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This manual documents Gambit-C. It covers release v4.6.1. +
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The Gambit programming system is a full implementation of the Scheme
+language which conforms to the R4RS, R5RS and IEEE Scheme standards. It
+consists of two main programs: gsi, the Gambit Scheme
+interpreter, and gsc, the Gambit Scheme compiler.
+
Gambit-C is a version of the Gambit programming system in which the +compiler generates portable C code, making the whole Gambit-C system and +the programs compiled with it easily portable to many computer +architectures for which a C compiler is available. With appropriate +declarations in the source code the executable programs generated by +the compiler run roughly as fast as equivalent C programs. +
+For the most up to date information on Gambit and add-on packages +please check the Gambit web page at +http://gambit.iro.umontreal.ca. The web page has links to the +Gambit mailing list, the bug reporting system, and the source code +repository. +
+| 1.1 Accessing the system files |
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+
Files related to Gambit, such as executables, libraries and header files, +are stored in multiple Gambit installation directories. +Gambit may be installed on a system according to two different +installation models. +
+In the first model there is a single directory where all the Gambit
+installation directories are stored. This central installation
+directory is typically /usr/local/Gambit-C under UNIX,
+/Library/Gambit-C under Mac OS X and C:/Program
+Files/Gambit-C under Microsoft Windows. This may have been
+overridden when the system was built with the command configure
+--prefix=/my/Gambit-C. If the system was built with the command
+configure --enable-multiple-versions then the central
+installation directory is prefix/version, where
+version is the system version string
+(e.g. v4.6.1 for Gambit v4.6.1). Moreover,
+prefix/current will be a symbolic link which points to
+the central installation directory. In this model, the Gambit
+installation directory named X is simply the subdirectory
+X of the central installation directory.
+
In the second model some or all of the Gambit installation directories +are stored in installation specific directories. The location of +these directories is assigned when the system is built using the +command configure --bindir=/my/bin --includedir=/my/include +--libdir=/my/lib. +
+The advantage of the first model is that it is easy to have multiple +versions of Gambit coexist and to remove all the files of a given +version. However, the second model may be necessary to conform to the +package installation conventions of some operating systems. +
+Executable programs such as the interpreter gsi and compiler
+gsc can be found in the bin installation directory.
+Adding this directory to the PATH environment variable allows
+these programs to be started by simply entering their name. This is
+done automatically by the Mac OS X and Microsoft Windows installers.
+
The runtime library is located in the lib installation
+directory. When the system’s runtime library is built as a
+shared-library (with the command configure --enable-shared) all
+programs built with Gambit-C, including the interpreter and compiler,
+need to find this library when they are executed and consequently this
+directory must be in the path searched by the system for
+shared-libraries. This path is normally specified through an
+environment variable which is LD_LIBRARY_PATH on most versions
+of UNIX, LIBPATH on AIX, SHLIB_PATH on HPUX,
+DYLD_LIBRARY_PATH on Mac OS X, and PATH on Microsoft
+Windows. If the shell is sh, the setting of the path can be
+made for a single execution by prefixing the program name with the
+environment variable assignment, as in:
+
$ LD_LIBRARY_PATH=/usr/local/Gambit-C/lib gsi + |
A similar problem exists with the Gambit header file gambit.h,
+located in the include installation directory. This header
+file is needed for compiling Scheme programs with the Gambit-C
+compiler. When the C compiler is being called explicitly it may be
+necessary to use a -I<dir> command line option to
+indicate where to find header files and a -L<dir> command
+line option to indicate where to find libraries.
+
Access to both of these files can be simplified by creating a link to +them in the appropriate system directories (special privileges may +however be required): +
+$ ln -s /usr/local/Gambit-C/lib/libgambc.a /usr/lib # name may vary
+$ ln -s /usr/local/Gambit-C/include/gambit.h /usr/include
+ |
Alternatively these files can be copied or linked in the directory +where the C compiler is invoked (this requires no special privileges). +
+Another approach is to set some environment variables which
+are used to tell the C compiler where to find header files
+and libraries. For example, the following settings can be
+used for the gcc C compiler:
+
$ export LIBRARY_PATH=/usr/local/Gambit-C/lib +$ export CPATH=/usr/local/Gambit-C/include + |
Note that this may have been done by the installation process. In
+particular, the Mac OS X and Microsoft Windows prebuilt installers set
+up the environment so that the gcc compiler finds these files
+automatically.
+
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Synopsis: +
+gsi [-:runtimeoption,…] [-i] [-f] [-v] [[-] [-e expressions] [file]]… + |
The interpreter is executed in interactive mode when no file or +- or -e option is given on the command line. Otherwise +the interpreter is executed in batch mode. The -i option +is ignored by the interpreter. The initialization file will be +examined unless the -f option is present (see section Customization). The -v option prints the system version +string, system time stamp, operating system type, and configure script +options on standard output and exits. Runtime options are explained +in Runtime options. +
+| 2.1 Interactive mode | ||
| 2.2 Batch mode | ||
| 2.3 Customization | ||
| 2.4 Process exit status | ||
| 2.5 Scheme scripts |
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+
In interactive mode a read-eval-print loop (REPL) is started for the +user to interact with the interpreter. At each iteration of this loop +the interpreter displays a prompt, reads a command and executes it. +The commands can be expressions to evaluate (the typical case) +or special commands related to debugging, for example ,q to +terminate the process (for a complete list of commands see +Debugging). Most commands produce some output, such as the +value or error message resulting from an evaluation. +
+The input and output of the interaction is done on the +interaction channel. The interaction channel can be specified +through the runtime options but if none is specified the system uses a +reasonable default that depends on the system’s configuration. When +the system’s runtime library was built with support for GUIDE, the +Gambit Universal IDE (with the command configure +--enable-guide) the interaction channel corresponds to the +console window of the primordial thread (for details see +GUIDE), otherwise the interaction channel is the user’s +console, also known as the controlling terminal in the +UNIX world. When the REPL starts, the ports associated with +(current-input-port), (current-output-port) and +(current-error-port) all refer to the interaction channel. +
+Expressions are evaluated in the global interaction environment.
+The interpreter adds to this environment any definition entered using
+the define and define-macro
+special forms. Once the evaluation of an expression is completed, the
+value or values resulting from the evaluation are output to the
+interaction channel by the pretty printer. The special “void”
+object is not output. This object is returned by most procedures and
+special forms which the Scheme standard defines as returning an
+unspecified value (e.g. write, set!, define).
+
Here is a sample interaction with gsi:
+
$ gsi +Gambit v4.6.1 + +> (define (fact n) (if (< n 2) 1 (* n (fact (- n 1))))) +> (map fact '(1 2 3 4 5 6)) +(1 2 6 24 120 720) +> (values (fact 10) (fact 40)) +3628800 +815915283247897734345611269596115894272000000000 +> ,q + |
What happens when errors occur is explained in Debugging. +
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+
In batch mode the command line arguments denote files to be loaded,
+REPL interactions to start (- option), and expressions to be
+evaluated (-e option). Note that the - and -e
+options can be interspersed with the files on the command line and can
+occur multiple times. The interpreter processes the command line
+arguments from left to right, loading files with the load
+procedure and evaluating expressions with the eval procedure in
+the global interaction environment. After this processing the
+interpreter exits.
+
When the file name has no extension the load procedure first
+attempts to load the file with no extension as a Scheme source file.
+If that file doesn’t exist it will search for both a source file and
+an object file. The object file’s name is obtained by adding to the
+file name a .on extension with the highest consecutive
+version number starting with 1. The source file’s name is obtained by
+adding to the file name the file extensions .scm and
+.six (the first found is the source file). If both a source
+file and an object file exist, then the one with the latest
+modification time is loaded. Otherwise the file that is found is
+loaded. When the file name has an extension, the load
+procedure will only attempt to load the file with that specific name.
+
When the extension of the file loaded is .scm the content of
+the file will be parsed using the normal Scheme prefix syntax. When
+the extension of the file loaded is .six the content of the
+file will be parsed using the Scheme infix syntax extension (see
+Scheme infix syntax extension). Otherwise, gsi will
+parse the file using the normal Scheme prefix syntax.
+
The ports associated with (current-input-port), +(current-output-port) and (current-error-port) initially +refer respectively to the standard input (stdin), standard +output (stdout) and the standard error (stderr) of the +interpreter. This is true even in REPLs started with the - +option. The usual interaction channel (console or IDE’s console +window) is still used to read expressions and commands and to display +results. This makes it possible to use REPLs to debug programs which +read the standard input and write to the standard output, even when +these have been redirected. +
+Here is a sample use of the interpreter in batch mode, under UNIX: +
+$ cat h.scm
+(display "hello") (newline)
+$ cat w.six
+display("world"); newline();
+$ gsi h.scm - w.six -e "(pretty-print 1)(pretty-print 2)"
+hello
+> (define (display x) (write (reverse (string->list x))))
+> ,(c 0)
+(#\d #\l #\r #\o #\w)
+1
+2
+ |
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There are two ways to customize the interpreter. When the interpreter +starts off it tries to execute a (load "~~lib/gambcext") (for an +explanation of how file names are interpreted see Host environment). +An error is not signaled when the file does not exist. Interpreter +extensions and patches that are meant to apply to all users and all +modes should go in that file. +
+Extensions which are meant to apply to a single user or to a specific
+working directory are best placed in the initialization file,
+which is a file containing Scheme code. In all modes, the interpreter
+first tries to locate the initialization file by searching the following
+locations: ‘.gambcini’ and ‘~/.gambcini’ (with no extension, a
+.scm extension, and a .six extension in that order). The
+first file that is found is examined as though the expression
+(include initialization-file) had been entered at the
+read-eval-print loop where initialization-file is the file that
+was found. Note that by using an include the macros defined in
+the initialization file will be visible from the read-eval-print loop
+(this would not have been the case if load had been used). The
+initialization file is not searched for or examined when the -f
+option is specified.
+
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The status is zero when the interpreter exits normally and is nonzero +when the interpreter exits due to an error. Here is the meaning of +the exit statuses: +
+0The execution of the primordial thread (i.e. the main thread) did not +encounter any error. It is however possible that other threads +terminated abnormally (by default threads other than the primordial +thread terminate silently when they raise an exception that is not +handled). +
+64The runtime options or the environment variable GAMBCOPT +contained a syntax error or were invalid. +
+70This normally indicates that an exception was raised in the primordial +thread and the exception was not handled. +
+71There was a problem initializing the runtime system, for example +insufficient memory to allocate critical tables. +
+For example, if the shell is sh:
+
$ gsi -:d0 -e "(pretty-print (expt 2 100))" +1267650600228229401496703205376 +$ echo $? +0 +$ gsi -:d0,unknown # try to use an unknown runtime option +$ echo $? +64 +$ gsi -:d0 nonexistent.scm # try to load a file that does not exist +$ echo $? +70 +$ gsi nonexistent.scm +*** ERROR IN ##main -- No such file or directory +(load "nonexistent.scm") +$ echo $? +70 + |
$ gsi -:m4000000 # ask for a 4 gigabyte heap
+*** malloc: vm_allocate(size=528384) failed (error code=3)
+*** malloc[15068]: error: Can't allocate region
+$ echo $?
+71
+ |
Note the use of the runtime option -:d0 that prevents error +messages from being output, and the runtime option -:m4000000 +which sets the minimum heap size to 4 gigabytes. +
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+
The load procedure treats specially files that begin with the
+two characters #! and @;. Such files are called
+script files and the first line is called the script line.
+In addition to indicating that the file is a script, the script line
+provides information about the source code language to be used by the
+load procedure. After the two characters #! and
+@; the system will search for the first substring matching one
+of the following language specifying tokens:
+
scheme-r4rsR4RS language with prefix syntax, case-insensitivity, keyword syntax +not supported +
+scheme-r5rsR5RS language with prefix syntax, case-insensitivity, keyword syntax +not supported +
+scheme-ieee-1178-1990IEEE 1178-1990 language with prefix syntax, case-insensitivity, keyword +syntax not supported +
+scheme-srfi-0R5RS language with prefix syntax and SRFI 0 support
+(i.e. cond-expand special form), case-insensitivity, keyword
+syntax not supported
+
gsi-scriptFull Gambit Scheme language with prefix syntax, case-sensitivity, keyword +syntax supported +
+gsc-scriptFull Gambit Scheme language with prefix syntax, case-sensitivity, keyword +syntax supported +
+six-scriptFull Gambit Scheme language with infix syntax, case-sensitivity, keyword +syntax supported +
+If a language specifying token is not found, load will use the
+same language as a nonscript file (i.e. it uses the file extension and
+runtime system options to determine the language).
+
After processing the script line, load will parse the rest of
+the file (using the syntax of the language indicated) and then execute
+it. When the file is being loaded because it is an argument on the
+interpreter’s command line, the interpreter will:
+
command-line procedure so that it returns a list
+containing the expanded file name of the script file and the
+arguments following the script file on the command line.
+This is done before the script is executed. The expanded file name
+of the script file can be used to determine the directory that
+contains the script (i.e. (path-directory (car (command-line)))).
+
+main is called with
+the command-line arguments. The way this is done depends on the
+language specifying token. For scheme-r4rs,
+scheme-r5rs, scheme-ieee-1178-1990, and
+scheme-srfi-0, the main procedure is called with the
+equivalent of (main (cdr (command-line))) and main is
+expected to return a process exit status code in the range 0 to 255.
+This conforms to the “Running Scheme Scripts on Unix SRFI” (SRFI
+22). For gsi-script and six-script the main
+procedure is called with the equivalent of (apply main (cdr
+(command-line))) and the process exit status code is 0 (main’s
+result is ignored). The Gambit-C system has a predefined main
+procedure which accepts any number of arguments and returns 0, so it
+is perfectly valid for a script to not define main and to do
+all its processing with top-level expressions (examples are given in
+the next section).
+
+main returns, the interpreter exits. The command-line
+arguments after a script file are consequently not processed (however
+they do appear in the list returned by the command-line
+procedure, after the script file’s expanded file name, so it is up to
+the script to process them).
+
+| 2.5.1 Scripts under UNIX and Mac OS X | ||
| 2.5.2 Scripts under Microsoft Windows | ||
| 2.5.3 Compiling scripts |
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Under UNIX and Mac OS X, the Gambit-C installation process creates the +executable gsi and also the executables six, +gsi-script, six-script, scheme-r5rs, +scheme-srfi-0, etc as links to gsi. A Scheme script +need only start with the name of the desired Scheme language variant +prefixed with #! and the directory where the Gambit-C +executables are stored. This script should be made executable by +setting the execute permission bits (with a chmod +x +script). Here is an example of a script which lists on standard +output the files in the current directory: +
+#!/usr/local/Gambit-C/bin/gsi-script +(for-each pretty-print (directory-files)) + |
Here is another UNIX script, using the Scheme infix syntax extension, +which takes a single integer argument and prints on standard output the +numbers from 1 to that integer: +
+#!/usr/local/Gambit-C/bin/six-script
+
+void main (obj n_str)
+{
+ int n = \string->number(n_str);
+ for (int i=1; i<=n; i++)
+ \pretty-print(i);
+}
+ |
For maximal portability it is a good idea to start scripts indirectly +through the /usr/bin/env program, so that the executable of the +interpreter will be searched in the user’s PATH. This is what +SRFI 22 recommends. For example here is a script that mimics the UNIX +cat utility for text files: +
+#!/usr/bin/env gsi-script + +(define (display-file filename) + (display (call-with-input-file filename + (lambda (port) + (read-line port #f))))) + +(for-each display-file (cdr (command-line))) + |
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Under Microsoft Windows, the Gambit-C installation process creates the +executable gsi.exe and six.exe and also the batch files +gsi-script.bat, six-script.bat, scheme-r5rs.bat, +scheme-srfi-0.bat, etc which simply invoke gsi.exe with +the same command line arguments. A Scheme script need only start with +the name of the desired Scheme language variant prefixed with +@;. A UNIX script can be converted to a Microsoft Windows +script simply by changing the script line and storing the script in a +file whose name has a .bat or .cmd extension: +
+@;gsi-script %~f0 %* +(display "files:\n") +(pretty-print (directory-files)) + |
Note that Microsoft Windows always searches executables in the user’s +PATH, so there is no need for an indirection such as the UNIX +/usr/bin/env. However the script line must end with %~f0 +%* to pass the expanded filename of the script and command line +arguments to the interpreter. +
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A script file can be compiled using the Gambit Scheme compiler +(see section The Gambit Scheme compiler) into a standalone executable. The script line will +provide information to the compiler on which language to use. The +script line also provides information on which runtime options to use +when executing the compiled script. This is useful to set the default +runtime options of an executable program. +
+The compiled script will be executed similarly to an interpreted
+script (i.e. the list of command line arguments returned by the
+command-line procedure and the invocation of the main
+procedure).
+
For example: +
+$ cat square.scm +#!/usr/local/Gambit-C/bin/gsi-script -:d0 +(define (main arg) + (pretty-print (expt (string->number arg) 2))) +$ gsi square 30 # gsi will load square.scm +900 +$ gsc -exe square # compile the script to a standalone program +$ ./square 30 +900 +$ ./square 1 2 3 # too many arguments to main +$ echo $? +70 +$ ./square -:d1 1 2 3 # ask for error message +*** ERROR -- Wrong number of arguments passed to procedure +(main "1" "2" "3") + |
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Synopsis: +
+gsc [-:runtimeoption,…] [-i] [-f] [-v] + [-prelude expressions] [-postlude expressions] + [-dynamic] [-exe] [-obj] [-cc-options options] + [-ld-options-prelude options] [-ld-options options] + [-warnings] [-verbose] [-report] [-expansion] [-gvm] + [-debug] [-debug-location] [-debug-source] + [-debug-environments] [-track-scheme] + [-o output] [-c] [-keep-c] [-link] [-flat] [-l base] + [[-] [-e expressions] [file]]… + |
| 3.1 Interactive mode | ||
| 3.2 Customization | ||
| 3.3 Batch mode | ||
| 3.4 Link files | ||
| 3.5 Procedures specific to compiler |
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When no command line argument is present other than options the
+compiler behaves like the interpreter in interactive mode. The only
+difference with the interpreter is that the compilation related
+procedures listed in this chapter are also available
+(i.e. compile-file, compile-file-to-c, etc).
+
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Like the interpreter, the compiler will examine the initialization +file unless the -f option is specified. +
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+
In batch mode gsc takes a set of file names (with either no
+extension, or a C file extension, or some other extension) on the
+command line and compiles each Scheme file into a C file.
+The recognized C file extensions are .c, .C, .cc,
+.cp, .cpp, .CPP, .cxx, .c++,
+.m, .M, and .mm.
+The extension can be omitted from file when the Scheme file has a
+.scm or .six extension. When the extension of the
+Scheme file is .six the content of the file will be parsed
+using the Scheme infix syntax extension (see Scheme infix syntax extension). Otherwise, gsc will parse the Scheme file using the
+normal Scheme prefix syntax. Files with a C file extension must
+have been previously produced by gsc, with the -c option,
+and are used by Gambit’s linker.
+
For each Scheme file a C file file.c will be produced. +The C file’s name is the same as the Scheme file, but the extension is +changed to .c. By default the C file is created in the same +directory as the Scheme file. This default can be overridden with the +compiler’s -o option. +
+The C files produced by the compiler serve two purposes. They will be +processed by a C compiler to generate object files, and they also +contain information to be read by Gambit’s linker to generate a +link file. The link file is a C file that collects various +linking information for a group of modules, such as the set of all +symbols and global variables used by the modules. + + +The linker is only invoked when the -link or -exe +options appear on the command line. +
+Compiler options must be specified before the first file name and +after the -: runtime option (see section Runtime options). If +present, the -i, -f, and -v compiler options +must come first. The available options are: +
+ + +-iForce interpreter mode. +
-fDo not examine the initialization file. +
-vPrint the system version string, system time stamp, operating system +type, and configure script options on standard output and exit. +
-prelude expressionsAdd expressions to the top of the source code being compiled. +
-postlude expressionsAdd expressions to the bottom of the source code being compiled. +
-cc-options optionsAdd options to the command that invokes the C compiler. +
-ld-options-prelude optionsAdd options to the command that invokes the C linker. +
-ld-options optionsAdd options to the command that invokes the C linker. +
-warningsDisplay warnings. +
-verboseDisplay a trace of the compiler’s activity. +
-reportDisplay a global variable usage report. +
-expansionDisplay the source code after expansion. +
-gvmGenerate a listing of the GVM code. +
-debugInclude all debugging information in the code generated. +
-debug-locationInclude source code location debugging information in the code generated. +
-debug-sourceInclude the source code debugging information in the code generated. +
-debug-environmentsInclude environment debugging information in the code generated. +
-track-schemeGenerate #line directives referring back to the Scheme code. +
-o outputSet name of output file or directory where output file(s) are written. +
-dynamicCompile Scheme source files to dynamically loadable object +files (this is the default). +
-exeCompile Scheme source files into an executable program. +
-objCompile Scheme source files to object files. +
-keep-cKeep any intermediate .c files that are generated. +
-cCompile Scheme source files to C without generating link file. +
-linkCompile Scheme source files to C and generate a link file. +
-flatGenerate a flat link file instead of the default incremental link file. +
-l baseSpecify the link file of the base library to use for the link. +
-Start REPL interaction. +
-e expressionsEvaluate expressions in the interaction environment. +
The -i option forces the compiler to process the remaining +command line arguments like the interpreter. +
+ +The -prelude option adds the specified expressions to the top of +the source code being compiled. The main use of this option is to +supply declarations on the command line. For example the following +invocation of the compiler will compile the file bench.scm in +unsafe mode: +
+$ gsc -prelude "(declare (not safe))" bench.scm + |
The -postlude option adds the specified expressions to the bottom +of the source code being compiled. The main use of this option is to +supply the expression that will start the execution of the program. For +example: +
+$ gsc -postlude "(start-bench)" bench.scm + |
The -cc-options option is only meaningful when a dynamically +loadable object file is being generated (neither the -c or +-link options are used). The -cc-options option adds +the specified options to the command that invokes the C compiler. The +main use of this option is to specify the include path, some symbols +to define or undefine, the optimization level, or any C compiler +option that is different from the default. For example: +
+$ gsc -cc-options "-U___SINGLE_HOST -O2 -I../include" bench.scm + |
The -ld-options-prelude and -ld-options options are only +meaningful when a dynamically loadable object file is being generated +(neither the -c or -link options are used). The +-ld-options-prelude and -ld-options options add the +specified options to the command that invokes the C linker (the +options in ld-options-prelude are passed to the C linker before +the input file and the options in ld-options are passed after). +The main use of this option is to specify additional object files or +libraries that need to be linked, or any C linker option that is +different from the default (such as the library search path and flags +to select between static and dynamic linking). For example: +
+$ gsc -ld-options "-L/usr/X11R6/lib -lX11 -dynamic" bench.scm + |
The -warnings option displays on standard output all warnings +that the compiler may have. +
+ +The -verbose option displays on standard output a trace of the +compiler’s activity. +
+ +The -report option displays on standard output a global +variable usage report. Each global variable used in the program is +listed with 4 flags that indicate whether the global variable is +defined, referenced, mutated and called. +
+ +The -expansion option displays on standard output the source code +after expansion and inlining by the front end. +
+ +The -gvm option generates a listing of the intermediate code +for the “Gambit Virtual Machine” (GVM) of each Scheme file on +file.gvm. +
+ + +The -debug option causes all kinds of debugging information to +be saved in the code generated. See the documentation of the +debug declaration for details. +
+ + +The -debug-location option causes source code location +debugging information to be saved in the code generated. See the +documentation of the debug-location declaration for details. +
+ + +The -debug-source option causes source code debugging +information to be saved in the code generated. See the documentation +of the debug-source declaration for details. +
+ + +The -debug-environments option causes environment debugging +information to be saved in the code generated. See the documentation +of the debug-environments declaration for details. +
+ +The -track-scheme options causes the generation of #line +directives that refer back to the Scheme source code. This allows the +use of a C debugger or profiler to debug Scheme code. +
+ +The -o option sets the filename of the output file, or the +directory in which the output file(s) generated by the compiler are +written. +
+ + + + + + + +If the -link or -exe options appear on the command line, +the Gambit linker is invoked to generate the link file from the set of +C files specified on the command line or produced by the Gambit +compiler. By default the link file is last_.c, where +last.c is the last file in the set of C files. When the +-c option is specified, the Scheme source files are compiled to +C files. When the -exe option is specified, the generated C +files and link file are compiled and linked using the C compiler to +produce an executable program whose name defaults to +last.exe. When the -obj option is specified, the +generated C files are compiled using the C compiler to produce object +files (.o or .obj extensions). If neither the +-link, -c, -exe, -obj options appear on +the command line, the Scheme source files are compiled to dynamically +loadable object files (.on extension). The +-keep-c option will prevent the deletion of any intermediate +.c file that is generated. Note that in this case the +intermediate .c file will be generated in the same directory as +the Scheme source file even if the -o option is used. +
+ +The -flat option is only meaningful when a link file is being +generated (i.e. the -link or -exe options also appear on +the command line). The -flat option directs the Gambit linker +to generate a flat link file. By default, the linker generates an +incremental link file (see the next section for a description of the +two types of link files). +
+ +The -l option is only meaningful when an incremental link file +is being generated (i.e. the -link or -exe options +appear on the command line and the -flat option is absent). +The -l option specifies the link file (without the .c +extension) of the base library to use for the incremental link. By +default the link file of the Gambit runtime library is used +(i.e. ~~lib/_gambc.c). +
+ +The - option starts a REPL interaction. +
+ +The -e option evaluates the specified expressions in the +interaction environment. +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
Gambit can be used to create programs and libraries of Scheme +modules. This section explains the steps required to do so and the role +played by the link files. +
+In general, a program is composed of a set of Scheme modules and C +modules. Some of the modules are part of the Gambit runtime library and +the other modules are supplied by the user. When the program is +started it must setup various global tables (including the symbol table +and the global variable table) and then sequentially execute the Scheme +modules (more or less as though they were being loaded one after another). +The information required for this is contained in one or more link +files generated by the Gambit linker from the C files produced by the +Gambit compiler. +
+The order of execution of the Scheme modules corresponds to the order of +the modules on the command line which produced the link file. The order +is usually important because most modules define variables and +procedures which are used by other modules (for this reason the +program’s main computation is normally started by the last module). +
+When a single link file is used to contain the linking information of +all the Scheme modules it is called a flat link file. Thus a +program built with a flat link file contains in its link file both +information on the user modules and on the runtime library. This is +fine if the program is to be statically linked but is wasteful in +a shared-library context because the linking information of the +runtime library can’t be shared and will be duplicated in all +programs (this linking information typically takes hundreds of kilobytes). +
+Flat link files are mainly useful to bundle multiple Scheme modules to
+make a runtime library (such as the Gambit runtime library) or to make a
+single file that can be loaded with the load procedure.
+
An incremental link file contains only the linking information +that is not already contained in a second link file (the “base” link +file). Assuming that a flat link file was produced when the runtime +library was linked, a program can be built by linking the user +modules with the runtime library’s link file, producing an incremental +link file. This allows the creation of a shared-library which +contains the modules of the runtime library and its flat link file. +The program is dynamically linked with this shared-library and +only contains the user modules and the incremental link file. For +small programs this approach greatly reduces the size of the +program because the incremental link file is small. A “hello +world” program built this way can be as small as 5 Kbytes. Note that +it is perfectly fine to use an incremental link file for statically +linked programs (there is very little loss compared to a single flat +link file). +
+Incremental link files may be built from other incremental link files. +This allows the creation of shared-libraries which extend the +functionality of the Gambit runtime library. +
+| 3.4.1 Building an executable program | ||
| 3.4.2 Building a loadable library | ||
| 3.4.3 Building a shared-library | ||
| 3.4.4 Other compilation options |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The simplest way to create an executable program is to invoke
+gsc with the -exe option. The compiler will
+transparently perform all the steps necessary, including compiling
+Scheme source files to C files, generating the link file, compiling
+the C files generated to object files, and creating the final
+executable file using the C linker. The following example shows how
+to build the executable program hello.exe which contains the
+two Scheme modules h.scm and w.six.
+
$ cat h.scm
+(display "hello") (newline)
+$ cat w.six
+display("world"); newline();
+$ gsc -o hello.exe -exe h.scm w.six
+h.scm:
+/Users/feeley/gambit/doc/h.c:
+w.six:
+/Users/feeley/gambit/doc/w.c:
+/Users/feeley/gambit/doc/w_.c:
+$ ./hello.exe
+hello
+world
+ |
The detailed steps which are performed can be viewed by setting the +GAMBC_CC_VERBOSE environment variable to a nonnull value. For +example: +
+$ export GAMBC_CC_VERBOSE=yes +$ gsc -o hello.exe -exe h.scm w.six +h.scm: +/Users/feeley/gambit/doc/h.c: +gcc -no-cpp-precomp -Wno-unused -O1 -fno-math-errno -fschedule-insns2 + -fno-trapping-math -fno-strict-aliasing -fwrapv -fomit-frame-pointer + -fPIC -fno-common -mieee-fp -I"/usr/local/Gambit-C/include" -c -o "h.o" h.c +w.six: +/Users/feeley/gambit/doc/w.c: +gcc -no-cpp-precomp -Wno-unused -O1 -fno-math-errno -fschedule-insns2 + -fno-trapping-math -fno-strict-aliasing -fwrapv -fomit-frame-pointer + -fPIC -fno-common -mieee-fp -I"/usr/local/Gambit-C/include" -c -o "w.o" w.c +/Users/feeley/gambit/doc/w_.c: +gcc -no-cpp-precomp -Wno-unused -O1 -fno-math-errno -fschedule-insns2 + -fno-trapping-math -fno-strict-aliasing -fwrapv -fomit-frame-pointer + -fPIC -fno-common -mieee-fp -I"/usr/local/Gambit-C/include" -c -o "w_.o" w_.c +gcc -no-cpp-precomp -Wno-unused -O1 -fno-math-errno -fschedule-insns2 + -fno-trapping-math -fno-strict-aliasing -fwrapv -fomit-frame-pointer + -fPIC -fno-common -mieee-fp -I"/usr/local/Gambit-C/include" + -o "hello.exe" h.o w.o w_.o "/usr/local/Gambit-C/lib/libgambc.a" + |
Using a single invocation of gsc with the -exe option is
+sometimes inappropriate when the build process is more complex, for
+example when the program is composed of several seperately compiled
+modules. In such a case it is useful to decompose the build process
+into smaller compilation steps. The hello.exe executable
+program could have been built by seperating the generation of C files
+from the C compilation and linking:
+
$ gsc -c h.scm +$ gsc -c w.six +$ gsc -o hello.exe -exe h.c w.c + |
When even finer control is desired the build process can be decomposed +into smaller steps that invoke the C compiler and linker explicitly. +This is described in the rest of this section. +
+The gsc compiler can be invoked to compile each Scheme module
+into a C file and to create an incremental link file. The C files and
+the link file must then be compiled with a C compiler and linked (at
+the object file level) with the Gambit runtime library and possibly
+other libraries (such as the math library and the dynamic loading
+library).
+
Here is for example how a program with three modules (one in C and two +in Scheme) can be built. The content of the three source files (m1.c, +m2.scm and m3.scm) is: +
+/* File: "m1.c" */
+int power_of_2 (int x) { return 1<<x; }
+
+; File: "m2.scm"
+(c-declare "extern int power_of_2 ();")
+(define pow2 (c-lambda (int) int "power_of_2"))
+(define (twice x) (cons x x))
+
+; File: "m3.scm"
+(write (map twice (map pow2 '(1 2 3 4)))) (newline)
+ |
The compilation of the two Scheme source files can be done with
+three invocations of gsc:
+
$ gsc -c m2.scm # create m2.c (note: .scm is optional) +$ gsc -c m3.scm # create m3.c (note: .scm is optional) +$ gsc -link m2.c m3.c # create the incremental link file m3_.c + |
Alternatively, the three invocations of gsc can be replaced by a
+single invocation:
+
$ gsc -link m2 m3 +m2: +m3: + |
At this point there will be 4 C files: m1.c, m2.c, +m3.c, and m3_.c. To produce an executable program these +files must be compiled with a C compiler and linked with the Gambit-C +runtime library. The C compiler options needed will depend on the C +compiler and the operating system (in particular it may be necessary +to add the options -I/usr/local/Gambit-C/include +-L/usr/local/Gambit-C/lib to access the gambit.h header file +and the Gambit-C runtime library). +
+Here is an example under Mac OS X: +
+$ uname -srmp +Darwin 8.1.0 Power Macintosh powerpc +$ gsc -obj m1.c m2.c m3.c m3_.c +m1.c: +m2.c: +m3.c: +m3_.c: +$ gcc m1.o m2.o m3.o m3_.o -lgambc +$ ./a.out +((2 . 2) (4 . 4) (8 . 8) (16 . 16)) + |
Here is an example under Linux: +
+$ uname -srmp +Linux 2.6.8-1.521 i686 athlon +$ gsc -obj m1.c m2.c m3.c m3_.c +m1.c: +m2.c: +m3.c: +m3_.c: +$ gcc m1.o m2.o m3.o m3_.o -lgambc -lm -ldl -lutil +$ ./a.out +((2 . 2) (4 . 4) (8 . 8) (16 . 16)) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
To bundle multiple modules into a single object file that can be
+dynamically loaded with the load procedure, a flat link file is
+needed. The compiler’s -o option must be used to name the C
+file generated as follows. If the dynamically loadable object file is
+to be named myfile.on then the -o option
+must set the name of the link file generated to
+myfile.on.c (note that the .c extension
+could also be .cc, .cpp or whatever extension is
+appropriate for C/C++ source files). The three modules of the
+previous example can be bundled by generating a link file in this way:
+
$ gsc -link -flat -o foo.o1.c m2 m3
+m2:
+m3:
+*** WARNING -- "cons" is not defined,
+*** referenced in: ("m2.c")
+*** WARNING -- "map" is not defined,
+*** referenced in: ("m3.c")
+*** WARNING -- "newline" is not defined,
+*** referenced in: ("m3.c")
+*** WARNING -- "write" is not defined,
+*** referenced in: ("m3.c")
+ |
The warnings indicate that there are no definitions (defines or
+set!s) of the variables cons, map, newline
+and write in the set of modules being linked. Before
+foo.o1 is loaded, these variables will have to be bound; either
+implicitly (by the runtime library) or explicitly.
+
When compiling the C files and link file generated, the flag +-D___DYNAMIC must be passed to the C compiler and the C +compiler and linker must be told to generate a dynamically loadable +shared library. +
+Here is an example under Mac OS X: +
+$ uname -srmp +Darwin 10.5.0 i386 i386 +$ gsc -link -flat -o foo.o1.c m2 m3 > /dev/null +m2: +m3: +$ gsc -cc-options "-D___DYNAMIC" -obj m1.c m2.c m3.c foo.o1.c +m1.c: +m2.c: +m3.c: +foo.o1.c: +$ gcc -bundle m1.o m2.o m3.o foo.o1.o -o foo.o1 +$ gsi foo.o1 +((2 . 2) (4 . 4) (8 . 8) (16 . 16)) + |
Here is an example under Linux: +
+$ uname -srmp +Linux 2.6.8-1.521 i686 athlon +$ gsc -link -flat -o foo.o1.c m2 m3 > /dev/null +m2: +m3: +$ gsc -cc-options "-D___DYNAMIC" -obj m1.c m2.c m3.c foo.o1.c +m1.c: +m2.c: +m3.c: +foo.o1.c: +$ gcc -shared m1.o m2.o m3.o foo.o1.o -o foo.o1 +$ gsi foo.o1 +((2 . 2) (4 . 4) (8 . 8) (16 . 16)) + |
Here is a more complex example, under Solaris, which shows how to build +a loadable library mymod.o1 composed of the files m4.scm, +m5.scm and x.c that links to system shared libraries (for +X-windows): +
+$ uname -srmp
+SunOS ungava 5.6 Generic_105181-05 sun4m sparc SUNW,SPARCstation-20
+$ gsc -link -flat -o mymod.o1.c m4 m5
+m4:
+m5:
+*** WARNING -- "*" is not defined,
+*** referenced in: ("m4.c")
+*** WARNING -- "+" is not defined,
+*** referenced in: ("m5.c")
+*** WARNING -- "display" is not defined,
+*** referenced in: ("m5.c" "m4.c")
+*** WARNING -- "newline" is not defined,
+*** referenced in: ("m5.c" "m4.c")
+*** WARNING -- "write" is not defined,
+*** referenced in: ("m5.c")
+$ gsc -cc-options "-D___DYNAMIC" -obj m4.c m5.c x.c mymod.o1.c
+m4.c:
+m5.c:
+x.c:
+mymod.o1.c:
+$ /usr/ccs/bin/ld -G -o mymod.o1 mymod.o1.o m4.o m5.o x.o -lX11 -lsocket
+$ gsi mymod.o1
+hello from m4
+hello from m5
+(f1 10) = 22
+$ cat m4.scm
+(define (f1 x) (* 2 (f2 x)))
+(display "hello from m4")
+(newline)
+
+(c-declare #<<c-declare-end
+#include "x.h"
+c-declare-end
+)
+(define x-initialize (c-lambda (char-string) bool "x_initialize"))
+(define x-display-name (c-lambda () char-string "x_display_name"))
+(define x-bell (c-lambda (int) void "x_bell"))
+$ cat m5.scm
+(define (f2 x) (+ x 1))
+(display "hello from m5")
+(newline)
+
+(display "(f1 10) = ")
+(write (f1 10))
+(newline)
+
+(x-initialize (x-display-name))
+(x-bell 50) ; sound the bell at 50%
+$ cat x.c
+#include <X11/Xlib.h>
+
+static Display *display;
+
+int x_initialize (char *display_name)
+{
+ display = XOpenDisplay (display_name);
+ return display != NULL;
+}
+
+char *x_display_name (void)
+{
+ return XDisplayName (NULL);
+}
+
+void x_bell (int volume)
+{
+ XBell (display, volume);
+ XFlush (display);
+}
+$ cat x.h
+int x_initialize (char *display_name);
+char *x_display_name (void);
+void x_bell (int);
+ |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
A shared-library can be built using an incremental link file or a flat +link file. An incremental link file is normally used when the Gambit +runtime library (or some other library) is to be extended with new +procedures. A flat link file is mainly useful when building a +“primal” runtime library, which is a library (such as the Gambit +runtime library) that does not extend another library. When compiling +the C files and link file generated, the flags -D___LIBRARY and +-D___SHARED must be passed to the C compiler. The flag +-D___PRIMAL must also be passed to the C compiler when a primal +library is being built. +
+A shared-library mylib.so containing the two first modules of +the previous example can be built this way: +
+$ uname -srmp +Linux bailey 1.2.13 #2 Wed Aug 28 16:29:41 GMT 1996 i586 +$ gsc -link -o mylib.c m2 +$ gsc -obj -cc-options "-D___SHARED" m1.c m2.c mylib.c +m1.c: +m2.c: +mylib.c: +$ gcc -shared m1.o m2.o mylib.o -o mylib.so + |
Note that this shared-library is built using an incremental link file
+(it extends the Gambit runtime library with the procedures pow2
+and twice). This shared-library can in turn be used to build
+an executable program from the third module of the previous example:
+
$ gsc -link -l mylib m3 +$ gsc -obj m3.c m3_.c +m3.c: +m3_.c: +$ gcc m3.o m3_.o mylib.so -lgambc +$ LD_LIBRARY_PATH=.:/usr/local/lib ./a.out +((2 . 2) (4 . 4) (8 . 8) (16 . 16)) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The performance of the code can be increased by passing the +-D___SINGLE_HOST flag to the C compiler. This will merge all +the procedures of a module into a single C procedure, which reduces +the cost of intra-module procedure calls. In addition the -O +option can be passed to the C compiler. For large modules, it will +not be practical to specify both -O and -D___SINGLE_HOST +for typical C compilers because the compile time will be high and the +C compiler might even fail to compile the program for lack of memory. +It has been observed that lower levels of optimization (e.g. -O1) +often give faster compilation and also generate faster code. It is +a good idea to experiment. +
+ + +Normally C compilers will not automatically search +/usr/local/Gambit-C/include for header files so the flag +-I/usr/local/Gambit-C/include should be passed to the C +compiler. Similarly, C compilers/linkers will not automatically +search /usr/local/Gambit-C/lib for libraries so the flag +-L/usr/local/Gambit-C/lib should be passed to the C +compiler/linker. Alternatives are given in Accessing the system files. +
+ + + + + + + + + + +A variety of flags are needed by some C compilers when compiling a +shared-library or a dynamically loadable library. Some of these flags +are: -shared, -call_shared, -rdynamic, +-fpic, -fPIC, -Kpic, -KPIC, -pic, ++z, -G. Check your compiler’s documentation to see +which flag you need. +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The Gambit Scheme compiler features the following procedures that +are not available in the Gambit Scheme interpreter. +
+ (compile-file-to-c file [options: options] [output: output] [module-name: module-name]) | procedure |
The file parameter must be a string naming an existing file
+containing Scheme source code. The extension can be omitted from
+file when the Scheme file has a .scm or .six
+extension. This procedure compiles the source file into a file
+containing C code. By default, this file is named after file
+with the extension replaced with .c. The name of the generated
+file can be specified with the output parameter. If
+output is a string naming a directory then the C file is created
+in that directory. Otherwise the name of the C file is output.
+The name of the generated module can be specified with the
+module-name parameter. If module-name is #f or is
+not specified, then the name of the module is derived from the name of
+the C file generated, without the extension.
+
Compilation options are specified through the options parameter +which must be a list of symbols. Any combination of the following +options can be used: verbose, report, expansion, +gvm, and debug. +
+When the compilation is successful, compile-file-to-c returns
+the name of the C file generated. When there is a compilation error,
+#f is returned.
+
$ cat h.scm +(display "hello") (newline) +$ gsc +Gambit v4.6.1 + +> (compile-file-to-c "h") +"/Users/feeley/gambit/doc/h.c" + |
(compile-file file [options: options] [output: output] [cc-options: cc-options] [ld-options-prelude: ld-options-prelude] [ld-options: ld-options]) | procedure |
The file, options, and output parameters have the
+same meaning as for the compile-file-to-c procedure, except that
+file may be a Scheme source file or a
+C file possibly generated by the Gambit Scheme compiler (for example
+with the compile-file-to-c procedure). The
+cc-options parameter is a string containing the options to pass
+to the C compiler and the ld-options-prelude and
+ld-options parameters are strings containing the options to pass
+to the C linker (the options in ld-options-prelude are passed to
+the C linker before the input file and the options in ld-options
+are passed after).
+
The compile-file procedure compiles the source file file
+into an object file, which is either a file dynamically loadable using
+the load procedure, or a C linkable object file destined to be
+linked with the C linker (for example to create a standalone
+executable program). The presence of the
+obj option in options will cause the creation of a C
+linkable object file and therefore the options
+ld-options-prelude and ld-options are ignored, otherwise a
+dynamically loadable file is created. In both cases, if file is
+a Scheme source file, the compiler first compiles file to a C
+file which is created in the same directory as file regardless
+of the output parameter. Then the C file is compiled with the C
+compiler.
+
When the compilation is successful, compile-file returns the
+name of the object file generated. When there is a compilation error,
+#f is returned.
+
The name of the object file can be specified with the output +parameter. If output is a string naming a directory then the +object file is created in that directory. Otherwise the name of the +object file is output. +
+In the case of a dynamically loadable object file, by default the
+object file is named after file with the extension replaced with
+.on, where n is a positive integer that acts as a
+version number. The next available version number is generated
+automatically by compile-file.
+
When dynamically loaded object files are loaded using the load
+procedure, the .on extension can be specified (to select
+a particular version) or omitted (to load the file with a
+.on extension with the highest n consecutively from
+1). When the .on extension is not specified and older
+versions are no longer needed, all versions must be deleted and the
+compilation must be repeated (this is necessary because the file name,
+including the extension, is used to name some of the exported symbols
+of the object file).
+
Note that dynamically loadable object files can only be generated on +host operating systems that support dynamic loading. +
+$ cat h.scm +(display "hello") (newline) +$ gsc +Gambit v4.6.1 + +> (compile-file "h") +"/Users/feeley/gambit/doc/h.o1" +> (load "h") +hello +"/Users/feeley/gambit/doc/h.o1" +> (compile-file-to-c "h" output: "h.o99.c") +"/Users/feeley/gambit/doc/h.o99.c" +> (compile-file "h.o99.c") +"/Users/feeley/gambit/doc/h.o99" +> (load "h.o99") +hello +"/Users/feeley/gambit/doc/h.o99" +> (compile-file-to-c "h") +"/Users/feeley/gambit/doc/h.c" +> (compile-file "h.c" options: '(obj)) +"/Users/feeley/gambit/doc/h.o" + |
(link-incremental module-list [output: output] [base: base] [warnings?: warnings?]) | procedure |
The first parameter must be a non empty list of strings naming Scheme +modules to link (the file extension may be omitted). An incremental link +file is generated for the modules specified in module-list. By +default the link file generated is named last_.c, where +last is the name of the last module, without the file extension. +The name of the generated +link file can be specified with the output parameter. If +output is a string naming a directory then the link file is +created in that directory. Otherwise the name of the link file is +output. +
+The base link file is specified by the base parameter, which +must be a string. By default the base link file is the Gambit runtime +library link file ~~lib/_gambc.c. However, when base is +supplied it is the name of the base link file (the file extension +may be omitted). +
+The warnings? parameter controls whether warnings are +generated for undefined references. +
+The following example shows how to build the executable program +hello which contains the two Scheme modules h.scm and +w.six. +
+$ uname -srmp
+Darwin 8.1.0 Power Macintosh powerpc
+$ cat h.scm
+(display "hello") (newline)
+$ cat w.six
+display("world"); newline();
+$ gsc
+Gambit v4.6.1
+
+> (compile-file-to-c "h")
+"/Users/feeley/gambit/doc/h.c"
+> (compile-file-to-c "w")
+"/Users/feeley/gambit/doc/w.c"
+> (link-incremental '("h" "w") output: "hello.c")
+"/Users/feeley/gambit/doc/hello_.c"
+> ,q
+$ gsc -obj h.c w.c hello.c
+h.c:
+w.c:
+hello.c:
+$ gcc h.o w.o hello.o -lgambc -o hello
+$ ./hello
+hello
+world
+ |
(link-flat module-list [output: output] [warnings?: warnings?]) | procedure |
The first parameter must be a non empty list of strings naming Scheme +modules to link (the file extension may be omitted). The first string +must be the name of a Scheme module +or the name of a link file and the remaining strings must name Scheme +modules. A flat link file +is generated for the modules specified in module-list. By +default the link file generated is named last_.c, where +last is the name of the last module. The name of the generated +link file can be specified with the output parameter. If +output is a string naming a directory then the link file is +created in that directory. Otherwise the name of the link file is +output. If a dynamically loadable object file is produced from +the link file output, then the name of the dynamically +loadable object file must be output stripped of its file +extension. +
+The warnings? parameter controls whether warnings are +generated for undefined references. +
+The following example shows how to build the dynamically loadable object +file lib.o1 which contains the two Scheme modules +m6.scm and m7.scm. +
+$ uname -srmp
+Darwin 8.1.0 Power Macintosh powerpc
+$ cat m6.scm
+(define (f x) (g (* x x)))
+$ cat m7.scm
+(define (g y) (+ n y))
+$ gsc
+Gambit v4.6.1
+
+> (compile-file-to-c "m6")
+"/Users/feeley/gambit/doc/m6.c"
+> (compile-file-to-c "m7")
+"/Users/feeley/gambit/doc/m7.c"
+> (link-flat '("m6" "m7") output: "lib.o1.c")
+*** WARNING -- "*" is not defined,
+*** referenced in: ("m6.c")
+*** WARNING -- "+" is not defined,
+*** referenced in: ("m7.c")
+*** WARNING -- "n" is not defined,
+*** referenced in: ("m7.c")
+"/Users/feeley/gambit/doc/lib.o1.c"
+> ,q
+$ gcc -bundle -D___DYNAMIC m6.c m7.c lib.o1.c -o lib.o1
+$ gsc
+Gambit v4.6.1
+
+> (load "lib")
+*** WARNING -- Variable "n" used in module "m7" is undefined
+"/Users/feeley/gambit/doc/lib.o1"
+> (define n 10)
+> (f 5)
+35
+> ,q
+ |
The warnings indicate that there are no definitions (defines or
+set!s) of the variables *, + and n in the
+modules contained in the library. Before the library is used, these
+variables will have to be bound; either implicitly (by the runtime
+library) or explicitly.
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
Both gsi and gsc as well as executable programs compiled
+and linked using gsc take a -: option which supplies
+parameters to the runtime system. This option must appear first on
+the command line. The colon is followed by a comma separated list of
+options with no intervening spaces. The available options are:
+
mHEAPSIZESet minimum heap size in kilobytes. +
hHEAPSIZESet maximum heap size in kilobytes. +
lLIVEPERCENTSet heap occupation after garbage collection. +
sSelect standard Scheme mode. +
SSelect Gambit Scheme mode. +
d[OPT...]Set debugging options. +
@[INTF][:PORT]Override the configuration of the main RPC server. +
=DIRECTORYOverride the central installation directory. +
~~DIR=DIRECTORYOverride the DIR installation directory. +
+ARGUMENTAdd ARGUMENT to the command line before other arguments. +
f[OPT...]Set file options. +
t[OPT...]Set terminal options. +
-[OPT...]Set standard input and output options. +
The m option specifies the minimum size of the heap. The +m is immediately followed by an integer indicating the number +of kilobytes of memory. The heap will not shrink lower than this +size. By default, the minimum size is 0. +
+ +The h option specifies the maximum size of the heap. The +h is immediately followed by an integer indicating the number +of kilobytes of memory. The heap will not grow larger than this size. +By default, there is no limit (i.e. the heap will grow until the +virtual memory is exhausted). +
+ +The l option specifies the percentage of the heap that will be +occupied with live objects after the heap is resized at the end of a +garbage collection. The l is immediately followed by an +integer between 1 and 100 inclusively indicating the desired +percentage. The garbage collector resizes the heap to reach this +percentage occupation. By default, the percentage is 50. +
+ + +The s option selects standard Scheme mode. In this mode the +reader is case-insensitive and keywords are not recognized. The +S option selects Gambit Scheme mode (the reader is case-sensitive +and recognizes keywords which end with a colon). By default Gambit +Scheme mode is used. +
+ +The d option sets various debugging options. The letter +d is followed by a sequence of letters indicating suboptions. +
+pUncaught exceptions will be treated as “errors” in the primordial thread +only. +
+aUncaught exceptions will be treated as “errors” in all threads. +
+rWhen an “error” occurs a new REPL will be started. +
+sWhen an “error” occurs a new REPL will be started. +Moreover the program starts in single-stepping mode. +
+qWhen an “error” occurs the program will terminate with a nonzero +exit status. +
+RWhen a user interrupt occurs a new REPL will be started. User +interrupts are typically obtained by typing <^C>. Note that with +some system configurations <^C> abruptly terminates the process. +For example, under Microsoft Windows, <^C> works fine with the +standard console but with the MSYS terminal window it terminates the +process. +
+DWhen a user interrupt occurs it will be deferred until the parameter
+current-user-interrupt-handler is bound.
+
QWhen a user interrupt occurs the program will terminate with a nonzero +exit status. +
+LEVELThe verbosity level is set to LEVEL (a digit from 0 to 9). +At level 0 the runtime system will not display error messages +and warnings. +
+iThe REPL interaction channel will be the IDE REPL window (if the IDE +is available). +
+cThe REPL interaction channel will be the console. +
+-The REPL interaction channel will be standard input and standard output. +
+@[HOST][:PORT]The REPL interaction channel will be connected to the remote debugger +at address HOST:PORT (if there is a remote debugger at +that address). The default HOST is 127.0.0.1 and the default +PORT is 44555. +THIS OPTION IS NOT YET IMPLEMENTED! +
+The default debugging options are equivalent to -:dpqQ1i
+(i.e. an uncaught exception in the primordial thread terminates the
+program after displaying an error message). When the letter d
+is not followed by suboptions, it is equivalent to -:dprR1i
+(i.e. a new REPL is started only when an uncaught exception occurs in
+the primordial thread). When gsi and gsc are running
+the main REPL, the debugging options are changed to cause errors in
+the primordial thread and user interrupts to start a nested REPL.
+
The @[INTF][:PORT] option +overrides the configuration of the main RPC server. The default +INTF is 127.0.0.1 and the default PORT is 44556. +THIS OPTION IS NOT YET IMPLEMENTED! +
+ +The =DIRECTORY option overrides the setting of the +central installation directory. +
+ +The ~~DIR=DIRECTORY option overrides the setting of +the DIR installation directory. +
+ +The + option adds the text that follows to the command line +before other arguments. +
+ + + +The f, t and - options specify the default +settings of the ports created for files, terminals and standard input +and output respectively. The default character encoding, end-of-line +encoding and buffering can be set. Moreover, for terminals the +line-editing feature can be enabled or disabled. The f, +t and - must be followed by a sequence of these options: +
+AASCII character encoding. +
1ISO-8859-1 character encoding. +
2UCS-2 character encoding. +
4UCS-4 character encoding. +
6UTF-16 character encoding. +
8UTF-8 character encoding. +
UUTF character encoding with fallback to UTF-8 on input if no BOM is present. +
UAUTF character encoding with fallback to ASCII on input if no BOM is present. +
U1UTF character encoding with fallback to ISO-8859-1 on input if no BOM is present. +
U6UTF character encoding with fallback to UTF-16 on input if no BOM is present. +
U8UTF character encoding with fallback to UTF-8 on input if no BOM is present. +
cEnd-of-line is encoded as CR (carriage-return). +
lEnd-of-line is encoded as LF (linefeed) +
clEnd-of-line is encoded as CR-LF. +
uUnbuffered I/O. +
nLine buffered I/O (n for “at newline”). +
fFully buffered I/O. +
rIllegal character encoding is treated as an error (exception raised). +
RSilently replace illegal character encodings with Unicode character #xfffd +(replacement character). +
eEnable line-editing (applies to terminals only). +
EDisable line-editing (applies to terminals only). +
When a program’s execution starts, the runtime system obtains the +runtime options by processing in turn four sources of runtime options: +the defaults, the environment variable GAMBCOPT, the script +line of the source code, and the first command line argument of the +program. Any runtime option can be overriden by a subsequent source +of runtime options. It is sometimes useful to prevent overriding +the runtime options of the script line. This can be achieved by +starting the script line runtime options with -::. In +this case the environment variable GAMBCOPT is ignored, +and the first command line argument of the program is +not used for runtime options (it is treated like a normal +command line argument). +
+For example: +
+$ GAMBCOPT=d0,=~/my-gambit2 +$ export GAMBCOPT +$ gsi -e '(pretty-print (path-expand "~~")) (/ 1 0)' +"/Users/feeley/my-gambit2/" +$ echo $? +70 +$ gsi -:d1 -e '(pretty-print (path-expand "~~")) (/ 1 0)' +"/Users/feeley/my-gambit2/" +*** ERROR IN (string)@1.3 -- Divide by zero +(/ 1 0) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
| 5.1 Debugging model | ||
| 5.2 Debugging commands | ||
| 5.3 Debugging example | ||
| 5.4 Procedures related to debugging | ||
| 5.5 Console line-editing | ||
| 5.6 Emacs interface | ||
| 5.7 GUIDE |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The evaluation of an expression may stop before it is completed for the +following reasons: +
+(step) was evaluated.
+
+When an evaluation stops, a message is displayed indicating the reason +and location where the evaluation was stopped. The location +information includes, if known, the name of the procedure where the +evaluation was stopped and the source code location in the format +stream@line.column, where stream is +either a string naming a file or a symbol within parentheses, such as +(console). +
+A nested REPL is then initiated in the context of the point of +execution where the evaluation was stopped. The nested REPL’s +continuation and evaluation environment are the same as the point where +the evaluation was stopped. For example when evaluating the expression +(let ((y (- 1 1))) (* (/ x y) 2)), a “divide by zero” error is +reported and the nested REPL’s continuation is the one that takes the +result and multiplies it by two. The REPL’s lexical environment +includes the lexical variable y. This allows the inspection of +the evaluation context (i.e. the lexical and dynamic environments and +continuation), which is particularly useful to determine the exact +location and cause of an error. +
+ +The prompt of nested REPLs includes the nesting level; 1> is the +prompt at the first nesting level, 2> at the second nesting +level, and so on. An end of file (usually <^D>) will cause the +current REPL to be terminated and the enclosing REPL (one nesting level +less) to be resumed. +
+At any time the user can examine the frames in the REPL’s +continuation, which is useful to determine which chain of procedure +calls lead to an error. A backtrace that lists the chain of active +continuation frames in the REPL’s continuation can be obtained with +the ,b command. The frames are numbered from 0, that is frame +0 is the most recent frame of the continuation where execution +stopped, frame 1 is the parent frame of frame 0, and so on. It is +also possible to move the REPL to a specific parent continuation +(i.e. a specific frame of the continuation where execution stopped) +with the ,N, ,N+, ,N-, +,+, ,-, ,++, and ,-- commands. When the +frame number of the frame being examined is not zero, it is shown in +the prompt after the nesting level, for example 1\5> is the +prompt when the REPL nesting level is 1 and the frame number is 5. +
+Expressions entered at a nested REPL are evaluated in the environment
+(both lexical and dynamic) of the continuation frame currently being
+examined if that frame was created by interpreted Scheme code. If the
+frame was created by compiled Scheme code then expressions get evaluated
+in the global interaction environment. This feature may be used in
+interpreted code to fetch the value of a variable in the current frame
+or to change its value with set!. Note that some special forms
+(define in particular) can only be evaluated in the global
+interaction environment.
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
In addition to expressions, the REPL accepts the following special +“comma” commands: +
+,?Give a summary of the REPL commands. +
+,(h subject)This command will show the section of the Gambit manual with the
+definition of the procedure or special form subject, which must
+be a symbol. For example ,(h time) will show the section
+documenting the time special form. Please see the help
+procedure for additional information.
+
,hThis command will show the section of the Gambit manual with the +definition of the procedure which raised the exception for which this +REPL was started. +
+,qTerminate the process with exit status 0. This is equivalent to
+calling (exit 0).
+
,qtTerminate the current thread (note that terminating the primordial +thread terminates the process). +
+,tReturn to the outermost REPL, also known as the “top-level REPL”. +
+,dLeave the current REPL and resume the enclosing REPL. This command does +nothing in the top-level REPL. +
+,(c expr)Leave the current REPL and continue the computation that initiated the +REPL with a specific value. This command can only be used to continue +a computation that signaled an error. The expression expr is +evaluated in the current context and the resulting value is returned +as the value of the expression which signaled the error. For example, +if the evaluation of the expression (* (/ x y) 2) signaled an +error because y is zero, then in the nested REPL a ,(c (+ +4 y)) will resume the computation of (* (/ x y) 2) as though +the value of (/ x y) was 4. This command must be used +carefully because the context where the error occured may rely on the +result being of a particular type. For instance a ,(c #f) in +the previous example will cause * to signal a type error (this +problem is the most troublesome when debugging Scheme code that was +compiled with type checking turned off so be careful). +
+,cLeave the current REPL and continue the computation that initiated the +REPL. This command can only be used to continue a computation that was +stopped due to a user interrupt, breakpoint or a single-step. +
+,sLeave the current REPL and continue the computation that initiated the
+REPL in single-stepping mode. The computation will perform an
+evaluation step (as defined by step-level-set!) and then stop,
+causing a nested REPL to be entered. Just before the evaluation step is
+performed, a line is displayed (in the same format as trace)
+which indicates the expression that is being evaluated. If the
+evaluation step produces a result, the result is also displayed on
+another line. A nested REPL is then entered after displaying a message
+which describes the next step of the computation. This command can
+only be used to continue a computation that was stopped due to a user
+interrupt, breakpoint or a single-step.
+
,lThis command is similar to ,s except that it “leaps” over +procedure calls, that is procedure calls are treated like a single step. +Single-stepping mode will resume when the procedure call returns, or if +and when the execution of the called procedure encounters a breakpoint. +
+,NMove to frame number N of the continuation. After changing the +current frame, a one-line summary of the frame is displayed as if the +,y command was entered. +
+,N+Move forward by N frames in the chain of continuation frames +(i.e. towards older continuation frames). After changing the current +frame, a one-line summary of the frame is displayed as if the +,y command was entered. +
+,N-Move backward by N frames in the chain of continuation frames +(i.e. towards more recent continuation frames). After changing the +current frame, a one-line summary of the frame is displayed as if the +,y command was entered. +
+,+Equivalent to ,1+. +
+,-Equivalent to ,1-. +
+,++Equivalent to ,N+ where N is the number of +continuation frames displayed at the head of a backtrace. +
+,--Equivalent to ,N- where N is the number of +continuation frames displayed at the head of a backtrace. +
+,yDisplay a one-line summary of the current frame. The information is +displayed in four fields. The first field is the frame number. The +second field is the procedure that created the frame or +(interaction) if the frame was created by an expression entered +at the REPL. The remaining fields describe the subproblem associated +with the frame, that is the expression whose value is being computed. +The third field is the location of the subproblem’s source code and +the fourth field is a reproduction of the source code, possibly +truncated to fit on the line. The last two fields may be missing if +that information is not available. In particular, the third field is +missing when the frame was created by a user call to the eval +procedure or by a compiled procedure not compiled with the declaration +debug-location, and the last field is missing when the frame +was created by a compiled procedure not compiled with the declaration +debug-source. +
+,bDisplay a backtrace summarizing each frame in the chain of continuation +frames starting with the current frame. For each frame, the same +information as for the ,y command is displayed (except that +location information is displayed in the format +stream@line:column). If there are more than 15 +frames in the chain of continuation frames, some of the middle frames +will be omitted. +
+,beLike the ,b command but also display the environment. +
+,bedLike the ,be command but also display the dynamic environment. +
+,(b expr)Display the backtrace of expr’s value, X, which is +obtained by evaluating expr in the current frame. X must +be a continuation or a thread. When X is a continuation, the +frames in that continuation are displayed. When X is a thread, +the backtrace of the current continuation of that thread is displayed. +
+,(be expr)Like the ,(b expr) command but also display the +environment. +
+,(bed expr)Like the ,(be expr) command but also display the dynamic +environment. +
+,iPretty print the procedure that created the current frame or +(interaction) if the frame was created by an expression entered +at the REPL. Compiled procedures will only be pretty printed when +they are compiled with the declaration debug-source. +
+,eDisplay the environment which is accessible from the current frame.
+The lexical environment is displayed, followed by the dynamic
+environment if the parameter object
+repl-display-dynamic-environment? is not false. Global lexical
+variables are not displayed. Moreover the frame must have been
+created by interpreted code or code compiled with the declaration
+debug-environments. Due to space safety
+considerations and compiler optimizations, some of the lexical
+variable bindings may be missing. Lexical variable bindings are
+displayed using the format variable = expression
+(when variable is mutable) or variable == expression
+(when variable is immutable, which may happen in compiled code
+due to compiler optimization)
+and dynamically-bound parameter bindings are displayed using the
+format (parameter) = expression. Note that
+expression can be a self-evaluating expression (number, string,
+boolean, character, ...), a quoted expression, a lambda expression or
+a global variable (the last two cases, which are only used when the
+value of the variable or parameter is a procedure, simplifies the
+debugging of higher-order procedures). A parameter can be a
+quoted expression or a global variable. Lexical bindings are
+displayed in inverse binding order (most deeply nested first) and
+shadowed variables are included in the list.
+
,edLike the ,e command but the dynamic environment is always +displayed. +
+,(e expr)Display the environment of expr’s value, X, which is +obtained by evaluating expr in the current frame. X must +be a continuation, a thread, a procedure, or a nonnegative integer. +When X is a continuation, the environment at that point in the +code is displayed. When X is a thread, the environment of the +current continuation of that thread is displayed. When X is a +procedure, the lexical environment where X was created is +combined with the current continuation and this combined environment +is displayed. When X is an integer, the environment at frame +number X of the continuation is displayed. +
+,(ed expr)Like the ,(e expr) command but the dynamic environment is +always displayed. +
+,stDisplay the state of the threads in the current thread’s thread group. +A thread can be: uninitialized, initialized, active, and +terminated (normally or abnormally). Active threads can be +running, sleeping and waiting on a synchronization object +(mutex, condition variable or port) possibly with a timeout. +
+,(st expr)Display the state of a specific thread or thread group. +The value of expr must be a thread or thread group. +
+,(v expr)Start a new REPL visiting expr’s value, X, which is +obtained by evaluating expr in the current frame. X must +be a continuation, a thread, a procedure, or a nonnegative integer. +When X is a continuation, the new REPL’s continuation is X +and evaluations are done in the environment at that point in the code. +When X is a thread, the thread is interrupted and the new REPL’s +continuation is the point where the thread was interrupted. When +X is a procedure, the lexical environment where X was +created is combined with the current continuation and evaluations are +done in this combined environment. When X is an integer, the +REPL is started in frame number X of the continuation. +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
Here is a sample interaction with gsi:
+
$ gsi +Gambit v4.6.1 + +> (define (invsqr x) (/ 1 (expt x 2))) +> (define (mymap fn lst) + (define (mm in) + (if (null? in) + '() + (cons (fn (car in)) (mm (cdr in))))) + (mm lst)) +> (mymap invsqr '(5 2 hello 9 1)) +*** ERROR IN invsqr, (console)@1.25 -- (Argument 1) NUMBER expected +(expt 'hello 2) +1> ,i +#<procedure #2 invsqr> = +(lambda (x) (/ 1 (expt x 2))) +1> ,e +x = 'hello +1> ,b +0 invsqr (console)@1:25 (expt x 2) +1 #<procedure #4> (console)@6:17 (fn (car in)) +2 #<procedure #4> (console)@6:31 (mm (cdr in)) +3 #<procedure #4> (console)@6:31 (mm (cdr in)) +4 (interaction) (console)@8:1 (mymap invsqr '(5 2 hel... +1> ,+ +1 #<procedure #4> (console)@6.17 (fn (car in)) +1\1> (pp #4) +(lambda (in) (if (null? in) '() (cons (fn (car in)) (mm (cdr in))))) +1\1> ,e +in = '(hello 9 1) +mm = (lambda (in) (if (null? in) '() (cons (fn (car in)) (mm (cdr in))))) +fn = invsqr +lst = '(5 2 hello 9 1) +1\1> ,(e mm) +mm = (lambda (in) (if (null? in) '() (cons (fn (car in)) (mm (cdr in))))) +fn = invsqr +lst = '(5 2 hello 9 1) +1\1> fn +#<procedure #2 invsqr> +1\1> (pp fn) +(lambda (x) (/ 1 (expt x 2))) +1\1> ,+ +2 #<procedure #4> (console)@6.31 (mm (cdr in)) +1\2> ,e +in = '(2 hello 9 1) +mm = (lambda (in) (if (null? in) '() (cons (fn (car in)) (mm (cdr in))))) +fn = invsqr +lst = '(5 2 hello 9 1) +1\2> ,(c (list 3 4 5)) +(1/25 1/4 3 4 5) +> ,q + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(help subject) | procedure |
(help-browser [new-value]) | procedure |
The help procedure displays the section of the Gambit manual
+with the definition of the procedure or special form subject,
+which must be a procedure or symbol. For example the call (help
+gensym) will show the section documenting the gensym procedure
+and the call (help 'time) will show the section documenting the
+time special form. The help procedure returns the void
+object.
+
The parameter object help-browser is bound to a string naming
+the external program that is used by the help procedure to view
+the documentation. Initially it is bound to the empty string. In
+normal circumstances when help-browser is bound to an empty
+string the help procedure runs the script
+~~bin/gambc-doc.bat which searches for a suitable web browser
+to open the documentation in HTML format. Unless the system was built
+with the command configure --enable-help-browser=..., the
+text-only browser lynx (see http://lynx.isc.org/) will
+be used by default if it is available. We highly recommend that you
+install this browser if you are interested in viewing the
+documentation within the console in which the REPL is running. You
+can exit lynx conveniently by typing an end of file (usually
+<^D>).
+
For example: +
+> (help-browser "firefox") ; use firefox instead of lynx +> (help 'gensym) +> (help gensym) ; OK because gensym is a procedure +> (help 'time) +> (help time) ; not OK because time is a special form +*** ERROR IN (console)@5.7 -- Macro name can't be used as a variable: time +> + |
(repl-result-history-ref i) | procedure |
(repl-result-history-max-length-set! n) | procedure |
The REPL keeps a history of the last few results printed by the
+REPL. The call (repl-result-history-ref i) returns the
+ith previous result (the last for i=0, the next to last
+for i=1, etc). By default the REPL result history remembers up
+to 3 results. The maximal length of the history can be set to n
+between 0 and 10 by a call to
+(repl-result-history-max-length-set! n).
+
For convenience the reader defines an abbreviation for calling
+repl-result-history-ref. Tokens formed by a sequence of one or
+more hash signs, such as #, ##, etc, are
+expanded by the reader into the list (repl-result-history-ref
+i), where i is the number of hash signs minus 1. In
+other words, # will return the last result printed by
+the REPL, ## will return the next to last, etc.
+
For example: +
+> (map (lambda (x) (* x x)) '(1 2 3)) +(1 4 9) +> (reverse #) +(9 4 1) +> (append # ##) +(9 4 1 1 4 9) +> 1 +1 +> 1 +1 +> (+ # ##) +2 +> (+ # ##) +3 +> (+ # ##) +5 +> #### +*** ERROR IN (console)@9.1 -- (Argument 1) Out of range +(repl-result-history-ref 3) +1> + |
(trace proc…) | procedure |
(untrace proc…) | procedure |
The trace procedure starts tracing calls to the specified
+procedures. When a traced procedure is called, a line containing the
+procedure and its arguments is displayed (using the procedure call
+expression syntax). The line is indented with a sequence of vertical
+bars which indicate the nesting depth of the procedure’s continuation.
+After the vertical bars is a greater-than sign which indicates that
+the evaluation of the call is starting.
+
When a traced procedure returns a result, it is displayed with the same +indentation as the call but without the greater-than sign. This makes +it easy to match calls and results (the result of a given call is the +value at the same indentation as the greater-than sign). If a traced +procedure P1 performs a tail call to a traced procedure P2, then P2 will +use the same indentation as P1. This makes it easy to spot tail calls. +The special handling for tail calls is needed to preserve the space +complexity of the program (i.e. tail calls are implemented as required +by Scheme even when they involve traced procedures). +
+The untrace procedure stops tracing calls to the specified
+procedures. When no argument is passed to the trace
+procedure, the list of procedures currently being traced is returned.
+The void object is returned by the trace procedure when it is
+passed one or more arguments. When no argument is passed to the
+untrace procedure stops all tracing and returns the void
+object. A compiled procedure may be traced but only if it is bound to
+a global variable.
+
For example: +
+> (define (fact n) (if (< n 2) 1 (* n (fact (- n 1))))) +> (trace fact) +> (fact 5) +| > (fact 5) +| | > (fact 4) +| | | > (fact 3) +| | | | > (fact 2) +| | | | | > (fact 1) +| | | | | 1 +| | | | 2 +| | | 6 +| | 24 +| 120 +120 +> (trace -) +*** WARNING -- Rebinding global variable "-" to an interpreted procedure +> (define (fact-iter n r) (if (< n 2) r (fact-iter (- n 1) (* n r)))) +> (trace fact-iter) +> (fact-iter 5 1) +| > (fact-iter 5 1) +| | > (- 5 1) +| | 4 +| > (fact-iter 4 5) +| | > (- 4 1) +| | 3 +| > (fact-iter 3 20) +| | > (- 3 1) +| | 2 +| > (fact-iter 2 60) +| | > (- 2 1) +| | 1 +| > (fact-iter 1 120) +| 120 +120 +> (trace) +(#<procedure #2 fact-iter> #<procedure #3 -> #<procedure #4 fact>) +> (untrace) +> (fact 5) +120 + |
(step) | procedure |
(step-level-set! level) | procedure |
The step procedure enables single-stepping mode. After the call
+to step the computation will stop just before the interpreter
+executes the next evaluation step (as defined by
+step-level-set!). A nested REPL is then started. Note that
+because single-stepping is stopped by the REPL whenever the prompt is
+displayed it is pointless to enter (step) by itself. On the
+other hand entering (begin (step) expr) will evaluate
+expr in single-stepping mode.
+
The procedure step-level-set! sets the stepping level which
+determines the granularity of the evaluation steps when single-stepping
+is enabled. The stepping level level must be an exact integer in
+the range 0 to 7. At a level of 0, the interpreter ignores
+single-stepping mode. At higher levels the interpreter stops the
+computation just before it performs the following operations, depending
+on the stepping level:
+
delay special form and operations at lower levels
+
+lambda special form and operations at lower levels
+
+define special form and operations at lower levels
+
+set! special form and operations at lower levels
+
+The default stepping level is 7. +
+For example: +
+> (define (fact n) (if (< n 2) 1 (* n (fact (- n 1))))) +> (step-level-set! 1) +> (begin (step) (fact 5)) +*** STOPPED IN (console)@3.15 +1> ,s +| > (fact 5) +*** STOPPED IN fact, (console)@1.22 +1> ,s +| | > (< n 2) +| | #f +*** STOPPED IN fact, (console)@1.43 +1> ,s +| | > (- n 1) +| | 4 +*** STOPPED IN fact, (console)@1.37 +1> ,s +| | > (fact (- n 1)) +*** STOPPED IN fact, (console)@1.22 +1> ,s +| | | > (< n 2) +| | | #f +*** STOPPED IN fact, (console)@1.43 +1> ,s +| | | > (- n 1) +| | | 3 +*** STOPPED IN fact, (console)@1.37 +1> ,l +| | | > (fact (- n 1)) +*** STOPPED IN fact, (console)@1.22 +1> ,l +| | > (* n (fact (- n 1))) +| | 24 +*** STOPPED IN fact, (console)@1.32 +1> ,l +| > (* n (fact (- n 1))) +| 120 +120 + |
(break proc…) | procedure |
(unbreak proc…) | procedure |
The break procedure places a breakpoint on each of the
+specified procedures. When a procedure is called that has a
+breakpoint, the interpreter will enable single-stepping mode (as if
+step had been called). This typically causes the computation
+to stop soon inside the procedure if the stepping level is high
+enough.
+
The unbreak procedure removes the breakpoints on the specified
+procedures. With no argument, break returns the list of
+procedures currently containing breakpoints. The void object is
+returned by break if it is passed one or more arguments. With
+no argument unbreak removes all the breakpoints and returns the
+void object. A breakpoint can be placed on a compiled procedure but
+only if it is bound to a global variable.
+
For example: +
+> (define (double x) (+ x x)) +> (define (triple y) (- (double (double y)) y)) +> (define (f z) (* (triple z) 10)) +> (break double) +> (break -) +*** WARNING -- Rebinding global variable "-" to an interpreted procedure +> (f 5) +*** STOPPED IN double, (console)@1.21 +1> ,b +0 double (console)@1:21 + +1 triple (console)@2:31 (double y) +2 f (console)@3:18 (triple z) +3 (interaction) (console)@6:1 (f 5) +1> ,e +x = 5 +1> ,c +*** STOPPED IN double, (console)@1.21 +1> ,c +*** STOPPED IN f, (console)@3.29 +1> ,c +150 +> (break) +(#<procedure #3 -> #<procedure #4 double>) +> (unbreak) +> (f 5) +150 + |
(generate-proper-tail-calls [new-value]) | procedure |
[Note: this procedure is DEPRECATED and will be removed +in a future version of Gambit. Use the proper-tail-calls +declaration instead.] +
+The parameter object generate-proper-tail-calls is bound to a
+boolean value controlling how the interpreter handles tail calls.
+When it is bound to #f the interpreter will treat tail calls
+like nontail calls, that is a new continuation will be created for the
+call. This setting is useful for debugging, because when a primitive
+signals an error the location information will point to the call site
+of the primitive even if this primitive was called with a tail call.
+The initial value of this parameter object is #t, which means
+that a tail call will reuse the continuation of the calling function.
+
This parameter object only affects code that is subsequently processed
+by load or eval, or entered at the REPL.
+
For example: +
+> (generate-proper-tail-calls) +#t +> (let loop ((i 1)) (if (< i 10) (loop (* i 2)) oops)) +*** ERROR IN #<procedure #2>, (console)@2.47 -- Unbound variable: oops +1> ,b +0 #<procedure #2> (console)@2:47 oops +1 (interaction) (console)@2:1 ((letrec ((loop (lambda... +1> ,t +> (generate-proper-tail-calls #f) +> (let loop ((i 1)) (if (< i 10) (loop (* i 2)) oops)) +*** ERROR IN #<procedure #3>, (console)@6.47 -- Unbound variable: oops +1> ,b +0 #<procedure #3> (console)@6:47 oops +1 #<procedure #3> (console)@6:32 (loop (* i 2)) +2 #<procedure #3> (console)@6:32 (loop (* i 2)) +3 #<procedure #3> (console)@6:32 (loop (* i 2)) +4 #<procedure #3> (console)@6:32 (loop (* i 2)) +5 (interaction) (console)@6:1 ((letrec ((loop (lambda... + + |
(display-environment-set! display?) | procedure |
[Note: this procedure is DEPRECATED and will be removed
+in a future version of Gambit. Use the parameter object
+repl-display-environment? instead.]
+
This procedure sets a flag that controls the automatic display of the +environment by the REPL. If display? is true, the environment +is displayed by the REPL before the prompt. The default setting is +not to display the environment. +
+ + + (repl-display-environment? display?) | procedure |
The parameter object repl-display-environment? is bound to a
+boolean value that controls the automatic display of the environment
+by the REPL. If display? is true, the environment is displayed
+by the REPL before the prompt. This is particularly useful in
+single-stepping mode. The default setting is not to display the
+environment.
+
(display-dynamic-environment? display?) | procedure |
The parameter object display-dynamic-environment? is bound to a
+boolean value that controls wether the dynamic environment is
+displayed when the environment is displayed. The default setting is
+not to display the dynamic environment.
+
(pretty-print obj [port]) | procedure |
This procedure pretty-prints obj on the port port. If it +is not specified, port defaults to the current output-port. +
+For example: +
+> (pretty-print + (let* ((x '(1 2 3 4)) (y (list x x x))) (list y y y))) +(((1 2 3 4) (1 2 3 4) (1 2 3 4)) + ((1 2 3 4) (1 2 3 4) (1 2 3 4)) + ((1 2 3 4) (1 2 3 4) (1 2 3 4))) + |
(pp obj [port]) | procedure |
This procedure pretty-prints obj on the port port. When +obj is a procedure created by the interpreter or a procedure +created by code compiled with the declaration +debug-source, the procedure’s source code is +displayed. If it is not specified, port defaults to the +interaction channel (i.e. the output will appear at the REPL). +
+For example: +
+> (define (f g) (+ (time (g 100)) (time (g 1000)))) +> (pp f) +(lambda (g) + (+ (##time (lambda () (g 100)) '(g 100)) + (##time (lambda () (g 1000)) '(g 1000)))) + |
(gc-report-set! report?) | procedure |
This procedure controls the generation of reports during garbage +collections. If the argument is true, a brief report of memory usage +is generated after every garbage collection. It contains: the time +taken for this garbage collection, the amount of memory allocated in +megabytes since the program was started, the size of the heap in +megabytes, the heap memory in megabytes occupied by live data, the +proportion of the heap occupied by live data, and the number of bytes +occupied by movable and nonmovable objects. +
+ + + |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The console implements a simple Scheme-friendly line-editing +user-interface that is enabled by default. It offers parentheses +balancing, a history of previous commands, symbol completion, and +several emacs-compatible keyboard commands. The user’s input is +displayed in a bold font and the output produced by the system is in a +plain font. The history of previous commands is saved in the file +‘~/.gambc_history’. It is restored when a REPL is started. +
+Symbol completion is triggered with the tab key. When the cursor is +after a sequence of characters that can form a symbol, typing the tab +key will search the symbol table for the first symbol (in alphabetical +order) that begins with that sequence and insert that symbol. Typing +the tab key in succession will cycle through all symbols with that +prefix. When all possible symbols have been shown or there are no +possible completions, the text reverts to the uncompleted symbol and +the bell is rung. +
+Here are the keyboard commands available (where the M-
+prefix means the escape key is typed and the C- prefix
+means the control key is pressed):
+
C-dGenerate an end-of-file when the line is empty, otherwise delete +character at cursor. +
+delete or backspaceDelete character before cursor. +
+M-C-dDelete word forward and keep a copy of this text on the clipboard. +
+M-deleteDelete word backward and keep a copy of this text on the clipboard. +
+M-backspaceDelete S-expression backward and keep a copy of this text on the clipboard. +
+C-aMove cursor to beginning of line. +
+C-eMove cursor to end of line. +
+C-b or left-arrowMove cursor left one character. +
+M-bMove cursor left one word. +
+M-C-b or M-left-arrowMove cursor left one S-expression. +
+C-f or right-arrowMove cursor right one character. +
+M-fMove cursor right one word. +
+M-C-f or M-right-arrowMove cursor right one S-expression. +
+C-p or M-p or up-arrowMove to previous line in history. +
+C-n or M-n or down-arrowMove to next line in history. +
+C-tTranspose character at cursor with previous character. +
+M-tTranspose word after cursor with previous word. +
+M-C-tTranspose S-expression after cursor with previous S-expression. +
+C-lClear console and redraw line being edited. +
+C-nulSet the mark to the cursor. +
+C-wDelete the text between the cursor and the mark and keep a copy +of this text on the clipboard. +
+C-kDelete the text from the cursor to the end of the line and keep a copy +of this text on the clipboard. +
+C-yPaste the text that is on the clipboard. +
+F8Same as typing #||#,c; (REPL command to continue the computation). +
+F9Same as typing #||#,-; (REPL command to move to newer frame). +
+F10Same as typing #||#,+; (REPL command to move to older frame). +
+F11Same as typing #||#,s; (REPL command to step the computation). +
+F12Same as typing #||#,l; (REPL command to leap the computation). +
+On Mac OS X, depending on your configuration, you may have to press
+the fn key to access the function key F12 and the
+option key to access the other function keys.
+
On Microsoft Windows the clipboard is the system clipboard. This +allows text to be copied and pasted between the program and other +applications. On other operating systems the clipboard is internal to +the program (it is not integrated with the operating system). +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
Gambit comes with the Emacs package gambit.el which provides a +nice environment for running Gambit from within the Emacs editor. +This package filters the standard output of the Gambit process and +when it intercepts a location information (in the format +stream@line.column where stream is +either (stdin) when the expression was obtained from standard +input, (console) when the expression was obtained from the +console, or a string naming a file) it opens a window to highlight the +corresponding expression. +
+To use this package, make sure the file gambit.el is accessible +from your load-path and that the following lines are in your +.emacs file: +
+(autoload 'gambit-inferior-mode "gambit" "Hook Gambit mode into cmuscheme.") +(autoload 'gambit-mode "gambit" "Hook Gambit mode into scheme.") +(add-hook 'inferior-scheme-mode-hook (function gambit-inferior-mode)) +(add-hook 'scheme-mode-hook (function gambit-mode)) +(setq scheme-program-name "gsi -:d-") + |
Alternatively, if you don’t mind always loading this package, +you can simply add this line to your .emacs file: +
+(require 'gambit) + |
You can then start an inferior Gambit process by typing M-x +run-scheme. The commands provided in cmuscheme mode will be +available in the Gambit interaction buffer (i.e. *scheme*) and in +buffers attached to Scheme source files. Here is a list of the most +useful commands (for a complete list type C-h m in the Gambit +interaction buffer): +
C-x C-eEvaluate the expression which is before the cursor (the expression will +be copied to the Gambit interaction buffer). +
C-c C-zSwitch to Gambit interaction buffer. +
C-c C-lLoad a file (file attached to current buffer is default) using
+(load file).
+
C-c C-kCompile a file (file attached to current buffer is default) using
+(compile-file file).
+
The file gambit.el provides these additional commands: +
+F8 or C-c cContinue the computation (same as typing #||#,c; to the REPL). +
F9 or C-c ]Move to newer frame (same as typing #||#,-; to the REPL). +
F10 or C-c [Move to older frame (same as typing #||#,+; to the REPL). +
F11 or C-c sStep the computation (same as typing #||#,s; to the REPL). +
F12 or C-c lLeap the computation (same as typing #||#,l; to the REPL). +
C-c _Removes the last window that was opened to highlight an expression. +
The two keystroke version of these commands can be shortened to +M-c, M-[, M-], M-s, M-l, and +M-_ respectively by adding this line to your .emacs +file: +
+(setq gambit-repl-command-prefix "\e") + |
This is more convenient to type than the two keystroke C-c based +sequences but the purist may not like this because it does not follow +normal Emacs conventions. +
+Here is what a typical .emacs file will look like: +
+(setq load-path ; add directory containing gambit.el + (cons "/usr/local/Gambit-C/share/emacs/site-lisp" + load-path)) +(setq scheme-program-name "/tmp/gsi -:d-") ; if gsi not in executable path +(setq gambit-highlight-color "gray") ; if you don't like the default +(setq gambit-repl-command-prefix "\e") ; if you want M-c, M-s, etc +(require 'gambit) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The implementation and documentation for GUIDE, the Gambit Universal +IDE, are not yet complete. +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
| 6.1 Extensions to standard procedures | ||
| 6.2 Extensions to standard special forms | ||
| 6.3 Miscellaneous extensions | ||
| 6.4 Undocumented extensions |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(transcript-on file) | procedure |
(transcript-off) | procedure |
These procedures do nothing. +
+ + + (call-with-current-continuation proc) | procedure |
(call/cc proc) | procedure |
The procedure call-with-current-continuation is bound to the
+global variables call-with-current-continuation and
+call/cc.
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(lambda lambda-formals body) | special form |
(define (variable define-formals) body) | special form |
( formal-argument-list ) | r4rs-lambda-formals
+. rest-formal-argument
+#!optional optional-formal-argument* | empty
+( variable initializer )
+#!rest rest-formal-argument | empty
+#!key keyword-formal-argument* | empty
+( variable initializer )
+( variable* ) |
+( variable+ . variable ) |
+variable
+. variable
+These forms are extended versions of the lambda and define
+special forms of standard Scheme. They allow the use of optional formal
+arguments, either positional or named, and support the syntax and semantics
+of the DSSSL standard.
+
When the procedure introduced by a lambda (or define) is
+applied to a list of actual arguments, the formal and actual arguments
+are processed as specified in the R4RS if the lambda-formals (or
+define-formals) is a r4rs-lambda-formals (or
+r4rs-define-formals).
+
If the formal-argument-list matches +dsssl-formal-argument-list or extended-formal-argument-list +they are processed as follows: +
+#f. The initializer is
+evaluated in an environment in which all previous formal arguments have
+been bound.
+
+#!key does not appear in the formal-argument-list
+and there is no rest-formal-argument then it shall be an error
+if there are any remaining actual arguments.
+
+#!key does not appear in the formal-argument-list
+and there is a rest-formal-argument then the
+rest-formal-argument is bound to a list of all remaining actual
+arguments.
+
+#!key appears in the formal-argument-list and there is
+no rest-formal-argument then there shall be an even number of
+remaining actual arguments. These are interpreted as a series of
+pairs, where the first member of each pair is a keyword specifying the
+argument name, and the second is the corresponding value. It shall be
+an error if the first member of a pair is not a keyword. It shall be
+an error if the argument name is not the same as a variable in a
+keyword-formal-argument. If the same argument name occurs more
+than once in the list of actual arguments, then the first value is
+used. If there is no actual argument for a particular
+keyword-formal-argument, then the variable is bound to the
+result of evaluating initializer if one was specified, and
+otherwise to #f. The initializer is evaluated in an
+environment in which all previous formal arguments have been bound.
+
+#!key appears in the formal-argument-list and there is
+a rest-formal-argument before the #!key then there
+may be an even or odd number of remaining actual arguments and the
+rest-formal-argument is bound to a list of all remaining actual
+arguments. Then, these remaining actual arguments are scanned from
+left to right in pairs, stopping at the first pair whose first element
+is not a keyword. Each pair whose first element is a keyword matching
+the name of a keyword-formal-argument gives the value (i.e. the
+second element of the pair) of the corresponding formal argument. If
+the same argument name occurs more than once in the list of actual
+arguments, then the first value is used. If there is no actual
+argument for a particular keyword-formal-argument, then the
+variable is bound to the result of evaluating initializer if one
+was specified, and otherwise to #f. The initializer is
+evaluated in an environment in which all previous formal arguments
+have been bound.
+
+#!key appears in the formal-argument-list and there is
+a rest-formal-argument after the #!key then there may
+be an even or odd number of remaining actual arguments. The remaining
+actual arguments are scanned from left to right in pairs, stopping at
+the first pair whose first element is not a keyword. Each pair shall
+have as its first element a keyword matching the name of a
+keyword-formal-argument; the second element gives the value of
+the corresponding formal argument. If the same argument name occurs
+more than once in the list of actual arguments, then the first value
+is used. If there is no actual argument for a particular
+keyword-formal-argument, then the variable is bound to the
+result of evaluating initializer if one was specified, and
+otherwise to #f. The initializer is evaluated in an
+environment in which all previous formal arguments have been bound.
+Finally, the rest-formal-argument is bound to the list of the
+actual arguments that were not scanned (i.e. after the last
+keyword/value pair).
+In all cases it is an error for a variable to appear more than +once in a formal-argument-list. +
+Note that this specification is compatible with the DSSSL language +standard (i.e. a correct DSSSL program will have the same semantics +when run with Gambit). +
+It is unspecified whether variables receive their value by binding or by
+assignment. Currently the compiler and interpreter use different
+methods, which can lead to different semantics if
+call-with-current-continuation is used in an initializer.
+Note that this is irrelevant for DSSSL programs because
+call-with-current-continuation does not exist in DSSSL.
+
For example: +
+> ((lambda (#!rest x) x) 1 2 3) +(1 2 3) +> (define (f a #!optional b) (list a b)) +> (define (g a #!optional (b a) #!key (k (* a b))) (list a b k)) +> (define (h1 a #!rest r #!key k) (list a k r)) +> (define (h2 a #!key k #!rest r) (list a k r)) +> (f 1) +(1 #f) +> (f 1 2) +(1 2) +> (g 3) +(3 3 9) +> (g 3 4) +(3 4 12) +> (g 3 4 k: 5) +(3 4 5) +> (g 3 4 k: 5 k: 6) +(3 4 5) +> (h1 7) +(7 #f ()) +> (h1 7 k: 8 9) +(7 8 (k: 8 9)) +> (h1 7 k: 8 z: 9) +(7 8 (k: 8 z: 9)) +> (h2 7) +(7 #f ()) +> (h2 7 k: 8 9) +(7 8 (9)) +> (h2 7 k: 8 z: 9) +*** ERROR IN (console)@17.1 -- Unknown keyword argument passed to procedure +(h2 7 k: 8 z: 9) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(vector-copy vector) | procedure |
This procedure returns a newly allocated vector with the same content +as the vector vector. Note that the elements are not +recursively copied. +
+For example: +
+> (define v1 '#(1 2 3)) +> (define v2 (vector-copy v1)) +> v2 +#(1 2 3) +> (eq? v1 v2) +#f + |
(subvector vector start end) | procedure |
This procedure is the vector analog of the substring
+procedure. It returns a newly allocated vector formed from the
+elements of the vector vector beginning with index start
+(inclusive) and ending with index end (exclusive).
+
For example: +
+> (subvector '#(a b c d e f) 3 5) +#(d e) + |
(vector-append vector…) | procedure |
This procedure is the vector analog of the string-append
+procedure. It returns a newly allocated vector whose elements
+form the concatenation of the given vectors.
+
For example: +
+> (define v '#(1 2 3)) +> (vector-append v v v) +#(1 2 3 1 2 3 1 2 3) + |
(append-vectors lst) | procedure |
This procedure returns a newly allocated vector whose elements form
+the concatenation of all the vectors in the list lst. It is
+equivalent to (apply vector-append lst).
+
For example: +
+> (define v '#(1 2 3)) +> (append-vectors (list v v v)) +#(1 2 3 1 2 3 1 2 3) + |
(subvector-fill! vector start end fill) | procedure |
This procedure is like vector-fill!, but fills a selected part
+of the given vector. It sets the elements of the vector vector,
+beginning with index start (inclusive) and ending with index
+end (exclusive) to fill. The value returned is
+unspecified.
+
For example: +
+> (define v (vector 'a 'b 'c 'd 'e 'f)) +> (subvector-fill! v 3 5 'x) +> v +#(a b c x x f) + |
(subvector-move! src-vector src-start src-end dst-vector dst-start) | procedure |
This procedure replaces part of the contents of vector +dst-vector with part of the contents of vector +src-vector. It copies elements from src-vector, beginning +with index src-start (inclusive) and ending with index +src-end (exclusive) to dst-vector beginning with index +dst-start (inclusive). The value returned is unspecified. +
+For example: +
+> (define v1 '#(1 2 3 4 5 6)) +> (define v2 (vector 'a 'b 'c 'd 'e 'f)) +> (subvector-move! v1 3 5 v2 1) +> v2 +#(a 4 5 d e f) + |
(vector-shrink! vector k) | procedure |
This procedure shortens the vector vector so that its new size +is k. The value returned is unspecified. +
+For example: +
+> (define v (vector 'a 'b 'c 'd 'e 'f)) +> v +#(a b c d e f) +> (vector-shrink! v 3) +> v +#(a b c) + |
(append-strings lst) | procedure |
This procedure returns a newly allocated string whose elements form
+the concatenation of all the strings in the list lst. It is
+equivalent to (apply string-append lst).
+
For example: +
+> (define s "abc") +> (append-strings (list s s s)) +"abcabcabc" + |
(substring-fill! string start end fill) | procedure |
This procedure is like string-fill!, but fills a selected part
+of the given string. It sets the elements of the string string,
+beginning with index start (inclusive) and ending with index
+end (exclusive) to fill. The value returned is
+unspecified.
+
For example: +
+> (define s (string #\a #\b #\c #\d #\e #\f)) +> (substring-fill! s 3 5 #\x) +> s +"abcxxf" + |
(substring-move! src-string src-start src-end dst-string dst-start) | procedure |
This procedure replaces part of the contents of string +dst-string with part of the contents of string +src-string. It copies elements from src-string, beginning +with index src-start (inclusive) and ending with index +src-end (exclusive) to dst-string beginning with index +dst-start (inclusive). The value returned is unspecified. +
+For example: +
+> (define s1 "123456") +> (define s2 (string #\a #\b #\c #\d #\e #\f)) +> (substring-move! s1 3 5 s2 1) +> s2 +"a45def" + |
(string-shrink! string k) | procedure |
This procedure shortens the string string so that its new size +is k. The value returned is unspecified. +
+For example: +
+> (define s (string #\a #\b #\c #\d #\e #\f)) +> s +"abcdef" +> (string-shrink! s 3) +> s +"abc" + |
(box obj) | procedure |
(box? obj) | procedure |
(unbox box) | procedure |
(set-box! box obj) | procedure |
These procedures implement the box data type. A box is a
+cell containing a single mutable field. The lexical syntax
+of a box containing the object obj is #&obj
+(see section Box syntax).
+
The procedure box returns a new box object whose content is
+initialized to obj. The procedure box? returns #t
+if obj is a box, and otherwise returns #f. The procedure
+unbox returns the content of the box box. The procedure
+set-box! changes the content of the box box to obj.
+The procedure set-box! returns an unspecified value.
+
For example: +
+> (define b (box 0)) +> b +#&0 +> (define (inc!) (set-box! b (+ (unbox b) 1))) +> (inc!) +> b +#&1 +> (unbox b) +1 + |
(keyword? obj) | procedure |
(keyword->string keyword) | procedure |
(string->keyword string) | procedure |
These procedures implement the keyword data type. Keywords are +similar to symbols but are self evaluating and distinct from the +symbol data type. The lexical syntax of keywords is specified in +Keyword syntax. +
+The procedure keyword? returns #t if obj is a
+keyword, and otherwise returns #f. The procedure
+keyword->string returns the name of keyword as a string.
+The procedure string->keyword returns the keyword whose name is
+string.
+
For example: +
+> (keyword? 'color) +#f +> (keyword? color:) +#t +> (keyword->string color:) +"color" +> (string->keyword "color") +color: + |
(gensym [prefix]) | procedure |
This procedure returns a new uninterned symbol. Uninterned symbols
+are guaranteed to be distinct from the symbols generated by the
+procedures read and string->symbol. The symbol
+prefix is the prefix used to generate the new symbol’s name. If
+it is not specified, the prefix defaults to g.
+
For example: +
+> (gensym) +#:g0 +> (gensym) +#:g1 +> (gensym 'star-trek-) +#:star-trek-2 + |
(make-uninterned-symbol name [hash]) | procedure |
(uninterned-symbol? obj) | procedure |
The procedure make-uninterned-symbol returns a new uninterned
+symbol whose name is name and hash is hash. The name must
+be a string and the hash must be a nonnegative fixnum.
+
The procedure uninterned-symbol? returns #t when
+obj is a symbol that is uninterned and #f otherwise.
+
For example: +
+> (uninterned-symbol? (gensym)) +#t +> (make-uninterned-symbol "foo") +#:foo: +> (uninterned-symbol? (make-uninterned-symbol "foo")) +#t +> (uninterned-symbol? 'hello) +#f +> (uninterned-symbol? 123) +#f + |
(make-uninterned-keyword name [hash]) | procedure |
(uninterned-keyword? obj) | procedure |
The procedure make-uninterned-keyword returns a new uninterned
+keyword whose name is name and hash is hash. The name must
+be a string and the hash must be a nonnegative fixnum.
+
The procedure uninterned-keyword? returns #t when
+obj is a keyword that is uninterned and #f otherwise.
+
For example: +
+> (make-uninterned-keyword "foo") +#:foo: +> (uninterned-keyword? (make-uninterned-keyword "foo")) +#t +> (uninterned-keyword? hello:) +#f +> (uninterned-keyword? 123) +#f + |
(void) | procedure |
This procedure returns the void object. The read-eval-print loop +prints nothing when the result is the void object. +
+ + + (eval expr [env]) | procedure |
The first parameter is a datum representing an expression. The
+eval procedure evaluates this expression in the global
+interaction environment and returns the result. If present, the
+second parameter is ignored (it is provided for compatibility with
+R5RS).
+
For example: +
+> (eval '(+ 1 2)) +3 +> ((eval 'car) '(1 2)) +1 +> (eval '(define x 5)) +> x +5 + |
(include file) | special form |
The file parameter must be a string naming an existing file
+containing Scheme source code. The include special form
+splices the content of the specified source file. This form can only
+appear where a define form is acceptable.
+
For example: +
+(include "macros.scm") + +(define (f lst) + (include "sort.scm") + (map sqrt (sort lst))) + |
(define-macro (name define-formals) body) | special form |
Define name as a macro special form which expands into body.
+This form can only appear where a define form is acceptable.
+Macros are lexically scoped. The scope of a local macro definition
+extends from the definition to the end of the body of the surrounding
+binding construct. Macros defined at the top level of a Scheme module
+are only visible in that module. To have access to the macro
+definitions contained in a file, that file must be included using the
+include special form. Macros which are visible from the REPL are
+also visible during the compilation of Scheme source files.
+
For example: +
+(define-macro (unless test . body) + `(if ,test #f (begin ,@body))) + +(define-macro (push var #!optional val) + `(set! ,var (cons ,val ,var))) + |
To examine the code into which a macro expands you can use the
+compiler’s -expansion option or the pp procedure.
+For example:
+
> (define-macro (push var #!optional val) + `(set! ,var (cons ,val ,var))) +> (pp (lambda () (push stack 1) (push stack) (push stack 3))) +(lambda () + (set! stack (cons 1 stack)) + (set! stack (cons #f stack)) + (set! stack (cons 3 stack))) + |
(define-syntax name expander) | special form |
Define name as a macro special form whose expansion is specified
+by expander. This form is available only when the runtime option
+-:s is used. This option causes the loading of the
+~~lib/syntax-case support library, which is the Hieb and Dybvig
+portable syntax-case implementation which has been ported to
+the Gambit interpreter and compiler. Note that this implementation of
+syntax-case does not support special forms that are specific to
+Gambit.
+
For example: +
+$ gsi -:s +Gambit v4.6.1 + +> (define-syntax unless + (syntax-rules () + ((unless test body ...) + (if test #f (begin body ...))))) +> (let ((test 111)) (unless (= 1 2) (list test test))) +(111 111) +> (pp (lambda () (let ((test 111)) (unless (= 1 2) (list test test))))) +(lambda () ((lambda (%%test14) (if (= 1 2) #f (list %%test14 %%test14))) 111)) +> (unless #f (pp xxx)) +*** ERROR IN (console)@7.16 -- Unbound variable: xxx + |
(declare declaration…) | special form |
This form introduces declarations to be used by the compiler
+(currently the interpreter ignores the declarations). This form can
+only appear where a define form is acceptable. Declarations
+are lexically scoped in the same way as macros. The following
+declarations are accepted by the compiler:
+
(dialect)Use the given dialect’s semantics. dialect can be: +ieee-scheme, r4rs-scheme, r5rs-scheme +or gambit-scheme. +
+(strategy)Select block compilation or separate compilation. In block +compilation, the compiler assumes that global variables defined in the +current file that are not mutated in the file will never be mutated. +strategy can be: block or separate. +
+([not] inline)Allow (or disallow) inlining of user procedures. +
+([not] inline-primitives primitive…)The given primitives should (or should not) be inlined +if possible (all primitives if none specified). +
+(inlining-limit n)Select the degree to which the compiler inlines user procedures.
+n is the upper-bound, in percent, on code expansion that will
+result from inlining. Thus, a value of 300 indicates that the size of
+the program will not grow by more than 300 percent (i.e. it will be at
+most 4 times the size of the original). A value of 0 disables inlining.
+The size of a program is the total number of subexpressions it contains
+(i.e. the size of an expression is one plus the size of its immediate
+subexpressions). The following conditions must hold for a procedure to
+be inlined: inlining the procedure must not cause the size of the call
+site to grow more than specified by the inlining limit, the site of
+definition (the define or lambda) and the call site must
+be declared as (inline), and the compiler must be able to find
+the definition of the procedure referred to at the call site (if the
+procedure is bound to a global variable, the definition site must have a
+(block) declaration). Note that inlining usually causes much
+less code expansion than specified by the inlining limit (an expansion
+around 10% is common for n=350).
+
([not] lambda-lift)Lambda-lift (or don’t lambda-lift) locally defined procedures. +
+([not] constant-fold)Allow (or disallow) constant-folding of primitive procedures. +
+([not] standard-bindings var…)The given global variables are known (or not known) to be equal to +the value defined for them in the dialect (all variables defined in +the standard if none specified). +
+([not] extended-bindings var…)The given global variables are known (or not known) to be equal to the +value defined for them in the runtime system (all variables defined +in the runtime if none specified). +
+([not] run-time-bindings var…)The given global variables will be tested at run time to see if they +are equal to the value defined for them in the runtime system (all +variables defined in the runtime if none specified). +
+([not] safe)Generate (or don’t generate) code that will prevent fatal errors at
+run time. Note that in safe mode certain semantic errors will
+not be checked as long as they can’t crash the system. For example
+the primitive char=? may disregard the type of its arguments in
+safe as well as not safe mode.
+
([not] interrupts-enabled)Generate (or don’t generate) interrupt checks. Interrupt checks are +used to detect user interrupts and also to check for stack overflows. +Interrupt checking should not be turned off casually. +
+([not] debug)Enable (or disable) the generation of debugging information. The kind +of debugging information that is generated depends on the declarations +debug-location, debug-source, and +debug-environments. If any of the command line options +-debug, -debug-location, -debug-source and +-debug-environments are present, the debug declaration +is initially enabled, otherwise it is initially disabled. When all +kinds of debugging information are generated there is a substantial +increase in the C compilation time and the size of the generated code. +When compiling a 3000 line Scheme file it was observed that the total +compilation time is 500% longer and the executable code is 150% +bigger. +
+([not] debug-location)Select (or deselect) source code location debugging information. When +this declaration and the debug declaration are in effect, run +time error messages indicate the location of the error in the source +code file. If any of the command line options -debug-source +and -debug-environments are present and -debug-location +is absent, the debug-location declaration is initially +disabled, otherwise it is initially enabled. When compiling a 3000 +line Scheme file it was observed that the total compilation time is +200% longer and the executable code is 60% bigger. +
+([not] debug-source)Select (or deselect) source code debugging information. When this
+declaration and the debug declaration are in effect, run time
+error messages indicate the source code, the backtraces are more
+precise, and the pp procedure will display the source code of
+compiled procedures. If any of the command line options
+-debug-location and -debug-environments are present and
+-debug-source is absent, the debug-source declaration is
+initially disabled, otherwise it is initially enabled. When compiling
+a 3000 line Scheme file it was observed that the total compilation
+time is 90% longer and the executable code is 90% bigger.
+
([not] debug-environments)Select (or deselect) environment debugging information. When this +declaration and the debug declaration are in effect, the +debugger will have access to the environments of the continuations. +In other words the local variables defined in compiled procedures (and +not optimized away by the compiler) will be shown by the ,e +REPL command. If any of the command line options +-debug-location and -debug-source are present and +-debug-environments is absent, the debug-environments +declaration is initially disabled, otherwise it is initially enabled. +When compiling a 3000 line Scheme file it was observed that the total +compilation time is 70% longer and the executable code is 40% bigger. +
+([not] proper-tail-calls)Generate (or don’t generate) proper tail calls. When proper tail
+calls are turned off, tail calls are handled like non-tail calls, that
+is a continuation frame will be created for all calls regardless of
+their kind. This is useful for debugging because the caller of a
+procedure will be visible in the backtrace produced by the REPL’s
+,b command even when the call is a tail call. Be advised that
+this does cause stack space to be consumed for tail calls which may
+cause the stack to overflow when performing long iterations with tail
+calls (whether they are expressed with a letrec, named
+let, do, or other form).
+
([not] optimize-dead-local-variables)Remove (or preserve) the dead local variables in the environment. +Preserving the dead local variables is useful for debugging because +continuations will contain the dead variables. Thus, if the code is +also compiled with the declaration debug-environments +the ,e, ,ed, ,be, and ,bed REPL +commands will display the dead variables. On the other hand, +preserving the dead local variables may change the space complexity of +the program (i.e. some of the data that would normally be reclaimed by +the garbage collector will not be). Note that due to other compiler +optimizations some dead local variables may be removed regardless of +this declaration. +
+(number-type primitive…)Numeric arguments and result of the specified primitives are +known to be of the given type (all primitives if none specified). +number-type can be: generic, fixnum, or +flonum. +
+(mostly-number-type primitive…)Numeric arguments and result of the specified primitives are expected +to be most often of the given type (all primitives if none specified). +mostly-number-type can be: mostly-generic, +mostly-fixnum, mostly-fixnum-flonum, +mostly-flonum, or mostly-flonum-fixnum. +
+The default declarations used by the compiler are equivalent to: +
+(declare + (gambit-scheme) + (separate) + (inline) + (inline-primitives) + (inlining-limit 350) + (constant-fold) + (lambda-lift) + (not standard-bindings) + (not extended-bindings) + (run-time-bindings) + (safe) + (interrupts-enabled) + (not debug) ;; depends on debugging command line options + (debug-location) ;; depends on debugging command line options + (debug-source) ;; depends on debugging command line options + (debug-environments) ;; depends on debugging command line options + (proper-tail-calls) + (optimize-dead-local-variables) + (generic) + (mostly-fixnum-flonum) +) + |
These declarations are compatible with the semantics of R5RS Scheme
+and includes a few procedures from R6RS (mainly fixnum specific and
+flonum specific procedures). Typically used declarations that enhance
+performance, at the cost of violating the R5RS Scheme semantics, are:
+(standard-bindings), (block), (not safe) and
+(fixnum).
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The procedures in this section are not yet documented. +
+ (continuation? obj) | procedure |
(continuation-capture proc) | procedure |
(continuation-graft cont proc obj…) | procedure |
(continuation-return cont obj…) | procedure |
These procedures provide access to internal first-class continuations +which are represented using continuation objects distinct from procedures. +
+The procedure continuation? returns #t when obj is
+a continuation object and #f otherwise.
+
The procedure continuation-capture is similar to the
+call/cc procedure but it represents the continuation with a
+continuation object. The proc parameter must be a procedure
+accepting a single argument. The procedure
+continuation-capture reifies its continuation and calls
+proc with the corresponding continuation object as its sole
+argument. Like for call/cc, the implicit continuation of the
+call to proc is the implicit continuation of the call to
+continuation-capture.
+
The procedure continuation-graft performs a procedure call to
+the procedure proc with arguments obj… and the
+implicit continuation corresponding to the continuation object
+cont. The current continuation of the call to procedure
+continuation-graft is ignored.
+
The procedure continuation-return invokes the implicit
+continuation corresponding to the continuation object cont with
+the result(s) obj…. This procedure can be easily
+defined in terms of continuation-graft:
+
(define (continuation-return cont . objs) + (continuation-graft (lambda () (apply values objs)))) + |
For example: +
+> (define x #f) +> (define p (make-parameter 11)) +> (pp (parameterize ((p 22)) + (cons 33 (continuation-capture + (lambda (c) (set! x c) 44))))) +(33 . 44) +> x +#<continuation #2> +> (continuation-return x 55) +(33 . 55) +> (continuation-graft x (lambda () (expt 2 10))) +(33 . 1024) +> (continuation-graft x expt 2 10) +(33 . 1024) +> (continuation-graft x (lambda () (p))) +(33 . 22) +> (define (map-sqrt1 lst) + (call/cc + (lambda (k) + (map (lambda (x) + (if (< x 0) + (k 'error) + (sqrt x))) + lst)))) +> (map-sqrt1 '(1 4 9)) +(1 2 3) +> (map-sqrt1 '(1 -1 9)) +error +> (define (map-sqrt2 lst) + (continuation-capture + (lambda (c) + (map (lambda (x) + (if (< x 0) + (continuation-return c 'error) + (sqrt x))) + lst)))) +> (map-sqrt2 '(1 4 9)) +(1 2 3) +> (map-sqrt2 '(1 -1 9)) +error + |
(display-exception exc [port]) | procedure |
(display-exception-in-context exc cont [port]) | procedure |
(display-procedure-environment proc [port]) | procedure |
(display-continuation-environment cont [port]) | procedure |
(display-continuation-dynamic-environment cont [port]) | procedure |
(display-continuation-backtrace cont [port [all-frames? [display-env? [max-head [max-tail [depth]]]]]]) | procedure |
The procedure display-continuation-backtrace displays the
+frames of the continuation corresponding to the continuation object
+cont on the port port. If it is not specified, port
+defaults to the current output-port. The frames are displayed in the
+same format as the REPL’s ,b command.
+
The parameter all-frames?, which defaults to #f, controls
+which frames are displayed. Some frames of ancillary importance, such
+as internal frames created by the interpreter, are not displayed when
+all-frames? is #f. Otherwise all frames are displayed.
+
The parameter display-env?, which defaults to #f, controls
+if the frames are displayed with its environment (the variables
+accessible and their bindings).
+
The parameters max-head and max-tail, which default to 10 +and 4 respectively, control how many frames are displayed at the head +and tail of the continuation. +
+The parameter depth, which defaults to 0, causes the frame numbers +to be offset by that value. +
+For example: +
+> (define x #f) +> (define (fib n) + (if (< n 2) + (continuation-capture + (lambda (c) (set! x c) 1)) + (+ (fib (- n 1)) + (fib (- n 2))))) +> (fib 10) +89 +> (display-continuation-backtrace x) +0 fib (console)@7:12 (fib (- n 2)) +1 fib (console)@7:12 (fib (- n 2)) +2 fib (console)@7:12 (fib (- n 2)) +3 fib (console)@7:12 (fib (- n 2)) +4 fib (console)@7:12 (fib (- n 2)) +5 (interaction) (console)@8:1 (fib 10) +#f +> (display-continuation-backtrace x (current-output-port) #t) +0 fib (console)@7:12 (fib (- n 2)) +1 fib (console)@6:9 (+ (fib (- n 1)) (fib (- ... +2 fib (console)@7:12 (fib (- n 2)) +3 fib (console)@6:9 (+ (fib (- n 1)) (fib (- ... +4 fib (console)@7:12 (fib (- n 2)) +5 fib (console)@6:9 (+ (fib (- n 1)) (fib (- ... +6 fib (console)@7:12 (fib (- n 2)) +7 fib (console)@6:9 (+ (fib (- n 1)) (fib (- ... +8 fib (console)@7:12 (fib (- n 2)) +9 fib (console)@6:9 (+ (fib (- n 1)) (fib (- ... +... +13 ##with-no-result-expected-toplevel +14 ##repl-debug +15 ##repl-debug-main +16 ##kernel-handlers +#f +> (display-continuation-backtrace x (current-output-port) #f #t) +0 fib (console)@7:12 (fib (- n 2)) + n = 2 +1 fib (console)@7:12 (fib (- n 2)) + n = 4 +2 fib (console)@7:12 (fib (- n 2)) + n = 6 +3 fib (console)@7:12 (fib (- n 2)) + n = 8 +4 fib (console)@7:12 (fib (- n 2)) + n = 10 +5 (interaction) (console)@8:1 (fib 10) +#f +> (display-continuation-backtrace x (current-output-port) #f #f 2 1 100) +100 fib (console)@7:12 (fib (- n 2)) +101 fib (console)@7:12 (fib (- n 2)) +... +105 (interaction) (console)@8:1 (fib 10) +#f + |
(make-thread-group [name [thread-group]]) | procedure |
(thread-group? obj) | procedure |
(thread-group-name thread-group) | procedure |
(thread-group-parent thread-group) | procedure |
(thread-group-resume! thread-group) | procedure |
(thread-group-suspend! thread-group) | procedure |
(thread-group-terminate! thread-group) | procedure |
(thread-group->thread-group-list thread-group) | procedure |
(thread-group->thread-group-vector thread-group) | procedure |
(thread-group->thread-list thread-group) | procedure |
(thread-group->thread-vector thread-group) | procedure |
(thread-state thread) | procedure |
(thread-state-uninitialized? thread-state) | procedure |
(thread-state-initialized? thread-state) | procedure |
(thread-state-active? thread-state) | procedure |
(thread-state-active-waiting-for thread-state) | procedure |
(thread-state-active-timeout thread-state) | procedure |
(thread-state-normally-terminated? thread-state) | procedure |
(thread-state-normally-terminated-result thread-state) | procedure |
(thread-state-abnormally-terminated? thread-state) | procedure |
(thread-state-abnormally-terminated-reason thread-state) | procedure |
(top [thread-group [port]]) | procedure |
(thread-interrupt! thread [thunk]) | procedure |
(thread-suspend! thread) | procedure |
(thread-resume! thread) | procedure |
(thread-thread-group thread) | procedure |
(define-type-of-thread name field…) | special form |
(thread-init! thread thunk [name [thread-group]]) | procedure |
(initialized-thread-exception? obj) | procedure |
(initialized-thread-exception-procedure exc) | procedure |
(initialized-thread-exception-arguments exc) | procedure |
(uninitialized-thread-exception? obj) | procedure |
(uninitialized-thread-exception-procedure exc) | procedure |
(uninitialized-thread-exception-arguments exc) | procedure |
(inactive-thread-exception? obj) | procedure |
(inactive-thread-exception-procedure exc) | procedure |
(inactive-thread-exception-arguments exc) | procedure |
(rpc-remote-error-exception? obj) | procedure |
(rpc-remote-error-exception-procedure exc) | procedure |
(rpc-remote-error-exception-arguments exc) | procedure |
(rpc-remote-error-exception-message exc) | procedure |
(timeout->time timeout) | procedure |
(open-dummy) | procedure |
(port-settings-set! port settings) | procedure |
(input-port-bytes-buffered port) | procedure |
(input-port-characters-buffered port) | procedure |
(nonempty-input-port-character-buffer-exception? obj) | procedure |
(nonempty-input-port-character-buffer-exception-arguments exc) | procedure |
(nonempty-input-port-character-buffer-exception-procedure exc) | procedure |
(repl-input-port) | procedure |
(repl-output-port) | procedure |
(console-port) | procedure |
(current-user-interrupt-handler [handler]) | procedure |
(defer-user-interrupts) | procedure |
(primordial-exception-handler exc) | procedure |
(err-code->string code) | procedure |
(foreign? obj) | procedure |
(foreign-tags foreign) | procedure |
(foreign-address foreign) | procedure |
(foreign-release! foreign) | procedure |
(foreign-released? foreign) | procedure |
(invalid-hash-number-exception? obj) | procedure |
(invalid-hash-number-exception-procedure exc) | procedure |
(invalid-hash-number-exception-arguments exc) | procedure |
(tcp-client-peer-socket-info tcp-client-port) | procedure |
(tcp-client-self-socket-info tcp-client-port) | procedure |
(tcp-server-socket-info tcp-server-port) | procedure |
(socket-info? obj) | procedure |
(socket-info-address socket-info) | procedure |
(socket-info-family socket-info) | procedure |
(socket-info-port-number socket-info) | procedure |
(system-version) | procedure |
(system-version-string) | procedure |
(system-type) | procedure |
(system-type-string) | procedure |
(configure-command-string) | procedure |
(system-stamp) | procedure |
(future expr) | special form |
(touch obj) | procedure |
(tty? obj) | procedure |
(tty-history tty) | procedure |
(tty-history-set! tty history) | procedure |
(tty-history-max-length-set! tty n) | procedure |
(tty-paren-balance-duration-set! tty duration) | procedure |
(tty-text-attributes-set! tty attributes) | procedure |
(tty-mode-set! tty mode) | procedure |
(tty-type-set! tty type) | procedure |
(with-input-from-port port thunk) | procedure |
(with-output-to-port port thunk) | procedure |
(input-port-char-position port) | procedure |
(output-port-char-position port) | procedure |
(open-event-queue n) | procedure |
(main …) | procedure |
(define-record-type …) | special form |
(define-type …) | special form |
(namespace …) | special form |
(this-source-file) | special form |
(receive …) | special form |
(cond-expand …) | special form |
(define-cond-expand-feature ident) | special form |
(finite? x) | procedure |
(infinite? x) | procedure |
(nan? x) | procedure |
(six.!) | undefined |
(six.!x x) | special form |
(six.&x x) | special form |
(six.*x x) | special form |
(six.++x x) | special form |
(six.+x x) | special form |
(six.--x x) | special form |
(six.-x x) | special form |
(six.arrow expr ident) | special form |
(six.break) | undefined |
(six.call func arg…) | special form |
(six.case) | undefined |
(six.clause) | undefined |
(six.compound statement…) | special form |
(six.cons x y) | special form |
(six.continue) | undefined |
(six.define-procedure ident proc) | special form |
(six.define-variable ident type dims init) | special form |
(six.do-while stat expr) | special form |
(six.dot expr ident) | special form |
(six.for stat1 expr2 expr3 stat2) | special form |
(six.goto) | undefined |
(six.identifier ident) | special form |
(six.if expr stat1 [stat2]) | special form |
(six.index expr1 expr2) | special form |
(six.label) | undefined |
(six.list x y) | special form |
(six.literal value) | special form |
(six.make-array init dim…) | procedure |
(six.new ident arg…) | special form |
(six.null) | special form |
(six.prefix datum) | special form |
(six.procedure type params stat) | special form |
(six.procedure-body stat…) | special form |
(six.return) | undefined |
(six.switch) | undefined |
(six.while expr stat…) | special form |
(six.x!=y x y) | special form |
(six.x%=y x y) | special form |
(six.x%y x y) | special form |
(six.x&&y x y) | special form |
(six.x&=y x y) | special form |
(six.x&y x y) | special form |
(six.x*=y x y) | special form |
(six.x*y x y) | special form |
(six.x++ x) | special form |
(six.x+=y x y) | special form |
(six.x+y x y) | special form |
(|six.x,y| x y) | special form |
(six.x-- x) | special form |
(six.x-=y x y) | special form |
(six.x-y x y) | special form |
(six.x/=y x y) | special form |
(six.x/y x y) | special form |
(six.x:-y x y) | undefined |
(six.x:=y x y) | special form |
(six.x:y x y) | special form |
(six.x<<=y x y) | special form |
(six.x<<y x y) | special form |
(six.x<=y x y) | special form |
(six.x<y x y) | special form |
(six.x==y x y) | special form |
(six.x=y x y) | special form |
(six.x>=y x y) | special form |
(six.x>>=y x y) | special form |
(six.x>>y x y) | special form |
(six.x>y x y) | special form |
(six.x?y:z x y z) | special form |
(six.x^=y x y) | special form |
(six.x^y x y) | special form |
(|six.x\|=y| x y) | special form |
(|six.x\|y| x y) | special form |
(|six.x\|\|y| x y) | special form |
(six.~x x) | special form |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
TO DO! +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
Gambit supports the Unicode character encoding standard. Scheme
+characters can be any of the characters whose Unicode encoding is in
+the range 0 to #x10ffff (inclusive) but not in the range #xd800 to
+#xdfff. Source code can also contain any Unicode character, however
+to read such source code properly gsi and gsc must be
+told which character encoding to use for reading the source code
+(i.e. ASCII, ISO-8859-1, UTF-8, etc). This can be done by specifying
+the runtime option -:f when gsi and gsc are
+started.
+
| 8.1 Extensions to character procedures | ||
| 8.2 Extensions to string procedures |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(char->integer char) | procedure |
(integer->char n) | procedure |
The procedure char->integer returns the Unicode encoding of
+the character char.
+
The procedure integer->char returns the character whose
+Unicode encoding is the exact integer n.
+
For example: +
+> (char->integer #\!) +33 +> (integer->char 65) +#\A +> (integer->char (char->integer #\u1234)) +#\u1234 +> (integer->char #xd800) +*** ERROR IN (console)@4.1 -- (Argument 1) Out of range +(integer->char 55296) + |
(char=? char1…) | procedure |
(char<? char1…) | procedure |
(char>? char1…) | procedure |
(char<=? char1…) | procedure |
(char>=? char1…) | procedure |
(char-ci=? char1…) | procedure |
(char-ci<? char1…) | procedure |
(char-ci>? char1…) | procedure |
(char-ci<=? char1…) | procedure |
(char-ci>=? char1…) | procedure |
These procedures take any number of arguments including no argument.
+This is useful to test if the elements of a list are sorted in a
+particular order. For example, testing that the list of characters
+lst is sorted in nondecreasing order can be done with the call
+(apply char<? lst).
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(string=? string1…) | procedure |
(string<? string1…) | procedure |
(string>? string1…) | procedure |
(string<=? string1…) | procedure |
(string>=? string1…) | procedure |
(string-ci=? string1…) | procedure |
(string-ci<? string1…) | procedure |
(string-ci>? string1…) | procedure |
(string-ci<=? string1…) | procedure |
(string-ci>=? string1…) | procedure |
These procedures take any number of arguments including no argument.
+This is useful to test if the elements of a list are sorted in a
+particular order. For example, testing that the list of strings
+lst is sorted in nondecreasing order can be done with the call
+(apply string<? lst).
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
| 9.1 Extensions to numeric procedures | ||
| 9.2 IEEE floating point arithmetic | ||
| 9.3 Integer square root and nth root | ||
| 9.4 Bitwise-operations on exact integers | ||
| 9.5 Fixnum specific operations | Operations on fixnums + | |
| 9.6 Flonum specific operations | Operations on flonums + | |
| 9.7 Pseudo random numbers |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(= z1…) | procedure |
(< x1…) | procedure |
(> x1…) | procedure |
(<= x1…) | procedure |
(>= x1…) | procedure |
These procedures take any number of arguments including no argument.
+This is useful to test if the elements of a list are sorted in a
+particular order. For example, testing that the list of numbers
+lst is sorted in nondecreasing order can be done with the call
+(apply < lst).
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
To better conform to IEEE floating point arithmetic the standard +numeric tower is extended with these special inexact reals: +
++inf.0positive infinity +
-inf.0negative infinity +
+nan.0“not a number” +
-0.negative zero (0. is the positive zero) +
The infinities and “not a number” are reals (i.e. (real?
++inf.0) is #t) but are not rational (i.e. (rational?
++inf.0) is #f).
+
Both zeros are numerically equal (i.e. (= -0. 0.) is #t)
+but are not equivalent (i.e. (eqv? -0. 0.) and (equal?
+-0. 0.) are #f). All numerical comparisons with “not a
+number”, including (= +nan.0 +nan.0), are #f.
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(integer-sqrt n) | procedure |
This procedure returns the integer part of the square root of the +nonnegative exact integer n. +
+For example: +
+> (integer-sqrt 123) +11 + |
(integer-nth-root n1 n2) | procedure |
This procedure returns the integer part of n1 raised to the +power 1/n2, where n1 is a nonnegative exact integer and +n2 is a positive exact integer. +
+For example: +
+> (integer-nth-root 100 3) +4 + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The procedures defined in this section are compatible with the +withdrawn “Integer Bitwise-operation Library SRFI” (SRFI 33). Note +that some of the procedures specified in SRFI 33 are not provided. +
+Most procedures in this section are specified in terms of the binary +representation of exact integers. The two’s complement representation +is assumed where an integer is composed of an infinite number of bits. +The upper section of an integer (the most significant bits) are either +an infinite sequence of ones when the integer is negative, or they are +an infinite sequence of zeros when the integer is nonnegative. +
+ (arithmetic-shift n1 n2) | procedure |
This procedure returns n1 shifted to the left by n2 bits,
+that is (floor (* n1 (expt 2 n2))). Both n1
+and n2 must be exact integers.
+
For example: +
+> (arithmetic-shift 1000 7) ; n1=...0000001111101000 +128000 +> (arithmetic-shift 1000 -6) ; n1=...0000001111101000 +15 +> (arithmetic-shift -23 -3) ; n1=...1111111111101001 +-3 + |
(bitwise-merge n1 n2 n3) | procedure |
This procedure returns an exact integer whose bits combine the bits +from n2 and n3 depending on n1. The bit at index +i of the result depends only on the bits at index i in +n1, n2 and n3: it is equal to the bit in n2 +when the bit in n1 is 0 and it is equal to the bit in n3 +when the bit in n1 is 1. All arguments must be exact integers. +
+For example: +
+> (bitwise-merge -4 -11 10) ; ...11111100 ...11110101 ...00001010 +9 +> (bitwise-merge 12 -11 10) ; ...00001100 ...11110101 ...00001010 +-7 + |
(bitwise-and n…) | procedure |
This procedure returns the bitwise “and” of the exact integers +n…. The value -1 is returned when there are no arguments. +
+For example: +
+> (bitwise-and 6 12) ; ...00000110 ...00001100 +4 +> (bitwise-and 6 -4) ; ...00000110 ...11111100 +4 +> (bitwise-and -6 -4) ; ...11111010 ...11111100 +-8 +> (bitwise-and) +-1 + |
(bitwise-ior n…) | procedure |
This procedure returns the bitwise “inclusive-or” of the exact +integers n…. The value 0 is returned when there are no +arguments. +
+For example: +
+> (bitwise-ior 6 12) ; ...00000110 ...00001100 +14 +> (bitwise-ior 6 -4) ; ...00000110 ...11111100 +-2 +> (bitwise-ior -6 -4) ; ...11111010 ...11111100 +-2 +> (bitwise-ior) +0 + |
(bitwise-xor n…) | procedure |
This procedure returns the bitwise “exclusive-or” of the exact +integers n…. The value 0 is returned when there are no +arguments. +
+For example: +
+> (bitwise-xor 6 12) ; ...00000110 ...00001100 +10 +> (bitwise-xor 6 -4) ; ...00000110 ...11111100 +-6 +> (bitwise-xor -6 -4) ; ...11111010 ...11111100 +6 +> (bitwise-xor) +0 + |
(bitwise-not n) | procedure |
This procedure returns the bitwise complement of the exact integer +n. +
+For example: +
+> (bitwise-not 3) ; ...00000011 +-4 +> (bitwise-not -1) ; ...11111111 +0 + |
(bit-count n) | procedure |
This procedure returns the bit count of the exact integer n. If +n is nonnegative, the bit count is the number of 1 bits in the +two’s complement representation of n. If n is negative, +the bit count is the number of 0 bits in the two’s complement +representation of n. +
+For example: +
+> (bit-count 0) ; ...00000000 +0 +> (bit-count 1) ; ...00000001 +1 +> (bit-count 2) ; ...00000010 +1 +> (bit-count 3) ; ...00000011 +2 +> (bit-count 4) ; ...00000100 +1 +> (bit-count -23) ; ...11101001 +3 + |
(integer-length n) | procedure |
This procedure returns the bit length of the exact integer n. +If n is a positive integer the bit length is one more than the +index of the highest 1 bit (the least significant bit is at index 0). +If n is a negative integer the bit length is one more than the +index of the highest 0 bit. If n is zero, the bit length is 0. +
+For example: +
+> (integer-length 0) ; ...00000000 +0 +> (integer-length 1) ; ...00000001 +1 +> (integer-length 2) ; ...00000010 +2 +> (integer-length 3) ; ...00000011 +2 +> (integer-length 4) ; ...00000100 +3 +> (integer-length -23) ; ...11101001 +5 + |
(bit-set? n1 n2) | procedure |
This procedure returns a boolean indicating if the bit at index +n1 of n2 is set (i.e. equal to 1) or not. Both n1 +and n2 must be exact integers, and n1 must be +nonnegative. +
+For example: +
+> (map (lambda (i) (bit-set? i -23)) ; ...11101001
+ '(7 6 5 4 3 2 1 0))
+(#t #t #t #f #t #f #f #t)
+ |
(any-bits-set? n1 n2) | procedure |
This procedure returns a boolean indicating if the bitwise and +of n1 and n2 is different from zero or not. This procedure +is implemented more efficiently than the naive definition: +
+(define (any-bits-set? n1 n2) (not (zero? (bitwise-and n1 n2)))) + |
For example: +
+> (any-bits-set? 5 10) ; ...00000101 ...00001010 +#f +> (any-bits-set? -23 32) ; ...11101001 ...00100000 +#t + |
(all-bits-set? n1 n2) | procedure |
This procedure returns a boolean indicating if the bitwise and +of n1 and n2 is equal to n1 or not. This procedure +is implemented more efficiently than the naive definition: +
+(define (all-bits-set? n1 n2) (= n1 (bitwise-and n1 n2))) + |
For example: +
+> (all-bits-set? 1 3) ; ...00000001 ...00000011 +#t +> (all-bits-set? 7 3) ; ...00000111 ...00000011 +#f + |
(first-bit-set n) | procedure |
This procedure returns the bit index of the least significant bit of
+n equal to 1 (which is also the number of 0 bits that are below
+the least significant 1 bit). This procedure returns -1 when
+n is zero.
+
For example: +
+> (first-bit-set 24) ; ...00011000 +3 +> (first-bit-set 0) ; ...00000000 +-1 + |
(extract-bit-field n1 n2 n3) | procedure |
(test-bit-field? n1 n2 n3) | procedure |
(clear-bit-field n1 n2 n3) | procedure |
(replace-bit-field n1 n2 n3 n4) | procedure |
(copy-bit-field n1 n2 n3 n4) | procedure |
These procedures operate on a bit-field which is n1 bits wide +starting at bit index n2. All arguments must be exact integers +and n1 and n2 must be nonnegative. +
+The procedure extract-bit-field returns the bit-field of
+n3 shifted to the right so that the least significant bit of the
+bit-field is the least significant bit of the result.
+
The procedure test-bit-field? returns #t if any bit in
+the bit-field of n3 is equal to 1, otherwise #f is
+returned.
+
The procedure clear-bit-field returns n3 with all bits
+in the bit-field replaced with 0.
+
The procedure replace-bit-field returns n4 with the
+bit-field replaced with the least-significant n1 bits of
+n3.
+
The procedure copy-bit-field returns n4 with the
+bit-field replaced with the (same index and size) bit-field in
+n3.
+
For example: +
+> (extract-bit-field 5 2 -37) ; ...11011011 +22 +> (test-bit-field? 5 2 -37) ; ...11011011 +#t +> (test-bit-field? 1 2 -37) ; ...11011011 +#f +> (clear-bit-field 5 2 -37) ; ...11011011 +-125 +> (replace-bit-field 5 2 -6 -37) ; ...11111010 ...11011011 +-21 +> (copy-bit-field 5 2 -6 -37) ; ...11111010 ...11011011 +-5 + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(fixnum? obj) | procedure |
(fx* n1…) | procedure |
(fx+ n1…) | procedure |
(fx- n1 n2…) | procedure |
(fx< n1…) | procedure |
(fx<= n1…) | procedure |
(fx= n1…) | procedure |
(fx> n1…) | procedure |
(fx>= n1…) | procedure |
(fxabs n) | procedure |
(fxand n1…) | procedure |
(fxarithmetic-shift n1 n2) | procedure |
(fxarithmetic-shift-left n1 n2) | procedure |
(fxarithmetic-shift-right n1 n2) | procedure |
(fxbit-count n) | procedure |
(fxbit-set? n1 n2) | procedure |
(fxeven? n) | procedure |
(fxfirst-bit-set n) | procedure |
(fxif n1 n2 n3) | procedure |
(fxior n1…) | procedure |
(fxlength n) | procedure |
(fxmax n1 n2…) | procedure |
(fxmin n1 n2…) | procedure |
(fxmodulo n1 n2) | procedure |
(fxnegative? n) | procedure |
(fxnot n) | procedure |
(fxodd? n) | procedure |
(fxpositive? n) | procedure |
(fxquotient n1 n2) | procedure |
(fxremainder n1 n2) | procedure |
(fxwrap* n1…) | procedure |
(fxwrap+ n1…) | procedure |
(fxwrap- n1 n2…) | procedure |
(fxwrapabs n) | procedure |
(fxwraparithmetic-shift n1 n2) | procedure |
(fxwraparithmetic-shift-left n1 n2) | procedure |
(fxwraplogical-shift-right n1 n2) | procedure |
(fxwrapquotient n1 n2) | procedure |
(fxxor n1…) | procedure |
(fxzero? n) | procedure |
(fixnum-overflow-exception? obj) | procedure |
(fixnum-overflow-exception-procedure exc) | procedure |
(fixnum-overflow-exception-arguments exc) | procedure |
Fixnum-overflow-exception objects are raised by some of the fixnum +specific procedures when the result is larger than can fit in a +fixnum. The parameter exc must be a fixnum-overflow-exception +object. +
+The procedure fixnum-overflow-exception? returns
+#t when obj is a fixnum-overflow-exception
+object and #f otherwise.
+
The procedure fixnum-overflow-exception-procedure
+returns the procedure that raised exc.
+
The procedure fixnum-overflow-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
For example: +
+> (define (handler exc) + (if (fixnum-overflow-exception? exc) + (list (fixnum-overflow-exception-procedure exc) + (fixnum-overflow-exception-arguments exc)) + 'not-fixnum-overflow-exception)) +> (with-exception-catcher + handler + (lambda () (fx* 100000 100000))) +(#<procedure #2 fx*> (100000 100000)) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(flonum? obj) | procedure |
(fixnum->flonum n) | procedure |
(fl* x1…) | procedure |
(fl+ x1…) | procedure |
(fl- x1 x2…) | procedure |
(fl/ x1 x2) | procedure |
(fl< x1…) | procedure |
(fl<= x1…) | procedure |
(fl= x1…) | procedure |
(fl> x1…) | procedure |
(fl>= x1…) | procedure |
(flabs x) | procedure |
(flacos x) | procedure |
(flasin x) | procedure |
(flatan x) | procedure |
(flatan y x) | procedure |
(flceiling x) | procedure |
(flcos x) | procedure |
(fldenominator x) | procedure |
(fleven? x) | procedure |
(flexp x) | procedure |
(flexpt x y) | procedure |
(flfinite? x) | procedure |
(flfloor x) | procedure |
(flinfinite? x) | procedure |
(flinteger? x) | procedure |
(fllog x) | procedure |
(flmax x1 x2…) | procedure |
(flmin x1 x2…) | procedure |
(flnan? x) | procedure |
(flnegative? x) | procedure |
(flnumerator x) | procedure |
(flodd? x) | procedure |
(flpositive? x) | procedure |
(flround x) | procedure |
(flsin x) | procedure |
(flsqrt x) | procedure |
(fltan x) | procedure |
(fltruncate x) | procedure |
(flzero? x) | procedure |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The procedures and variables defined in this section are compatible +with the “Sources of Random Bits SRFI” (SRFI 27). The +implementation is based on Pierre L’Ecuyer’s MRG32k3a pseudo random +number generator. At the heart of SRFI 27’s interface is the random +source type which encapsulates the state of a pseudo random number +generator. The state of a random source object changes every time a +pseudo random number is generated from this random source object. +
+ (default-random-source) | variable |
The global variable default-random-source is bound to the
+random source object which is used by the random-integer,
+random-real, random-u8vector and random-f64vector
+procedures.
+
(random-integer n) | procedure |
This procedure returns a pseudo random exact integer in the range 0 to
+n-1. The random source object in the global variable
+default-random-source is used to generate this number. The
+parameter n must be a positive exact integer.
+
For example: +
+> (random-integer 100) +24 +> (random-integer 100) +2 +> (random-integer 10000000000000000000000000000000000000000) +6143360270902284438072426748425263488507 + |
(random-real) | procedure |
This procedure returns a pseudo random inexact real between, but not
+including, 0 and 1. The random source object in the global variable
+default-random-source is used to generate this number.
+
For example: +
+> (random-real) +.24230672079133753 +> (random-real) +.02317001922506932 + |
(random-u8vector n) | procedure |
This procedure returns a u8vector of length n containing pseudo
+random exact integers in the range 0 to 255. The random source object
+in the global variable default-random-source is used to
+generate these numbers. The parameter n must be a nonnegative
+exact integer.
+
For example: +
+> (random-u8vector 10) +#u8(200 53 29 202 3 85 208 187 73 219) + |
(random-f64vector n) | procedure |
This procedure returns a f64vector of length n containing pseudo
+random inexact reals between, but not including, 0 and 1. The random
+source object in the global variable default-random-source is
+used to generate these numbers. The parameter n must be a nonnegative
+exact integer.
+
For example: +
+> (random-f64vector 3) +#f64(.7145854494613069 .47089632669147946 .5400124875182746) + |
(make-random-source) | procedure |
This procedure returns a new random source object initialized to a
+predetermined state (to initialize to a pseudo random state the
+procedure random-source-randomize! should be called).
+
For example: +
+> (define rs (make-random-source)) +> ((random-source-make-integers rs) 10000000) +8583952 + |
(random-source? obj) | procedure |
This procedure returns #t when obj is a random source
+object and #f otherwise.
+
For example: +
+> (random-source? default-random-source) +#t +> (random-source? 123) +#f + |
(random-source-state-ref random-source) | procedure |
(random-source-state-set! random-source state) | procedure |
The procedure random-source-state-ref extracts the state of
+the random source object random-source and returns a vector
+containing the state.
+
The procedure random-source-state-set! restores the state of
+the random source object random-source to state which must
+be a vector returned from a call to the procedure
+random-source-state-ref.
+
For example: +
+> (define s (random-source-state-ref default-random-source)) +> (random-integer 10000000000000000000000000000000000000000) +7583880188903074396261960585615270693321 +> (random-source-state-set! default-random-source s) +> (random-integer 10000000000000000000000000000000000000000) +7583880188903074396261960585615270693321 + |
(random-source-randomize! random-source) | procedure |
(random-source-pseudo-randomize! random-source i j) | procedure |
These procedures change the state of the random source object
+random-source. The procedure random-source-randomize!
+sets the random source object to a state that depends on the current
+time (which for typical uses can be considered to randomly initialize
+the state). The procedure random-source-pseudo-randomize!
+sets the random source object to a state that is determined only by
+the current state and the nonnegative exact integers i and
+j. For both procedures the value returned is unspecified.
+
For example: +
+> (define s (random-source-state-ref default-random-source)) +> (random-source-pseudo-randomize! default-random-source 5 99) +> (random-integer 10000000000000000000000000000000000000000) +9816755163910623041601722050112674079767 +> (random-source-state-set! default-random-source s) +> (random-source-pseudo-randomize! default-random-source 5 99) +> (random-integer 10000000000000000000000000000000000000000) +9816755163910623041601722050112674079767 +> (random-source-pseudo-randomize! default-random-source 5 99) +> (random-integer 10000000000000000000000000000000000000000) +9816755163910623041601722050112674079767 +> (random-source-state-set! default-random-source s) +> (random-source-randomize! default-random-source) +> (random-integer 10000000000000000000000000000000000000000) +2271441220851914333384493143687768110622 +> (random-source-state-set! default-random-source s) +> (random-source-randomize! default-random-source) +> (random-integer 10000000000000000000000000000000000000000) +6247966138948323029033944059178072366895 + |
(random-source-make-integers random-source) | procedure |
This procedure returns a procedure for generating pseudo random exact +integers using the random source object random-source. The +returned procedure accepts a single parameter n, a positive +exact integer, and returns a pseudo random exact integer in the range +0 to n-1. +
+For example: +
+> (define rs (make-random-source)) +> (define ri (random-source-make-integers rs)) +> (ri 10000000) +8583952 +> (ri 10000000) +2879793 + |
(random-source-make-reals random-source [precision]) | procedure |
This procedure returns a procedure for generating pseudo random +inexact reals using the random source object random-source. The +returned procedure accepts no parameters and returns a pseudo random +inexact real between, but not including, 0 and 1. The optional parameter +precision specifies an upper bound on the minimum amount by which two +generated pseudo-random numbers can be separated. +
+For example: +
+> (define rs (make-random-source)) +> (define rr (random-source-make-reals rs)) +> (rr) +.857402537562821 +> (rr) +.2876463473845367 + |
(random-source-make-u8vectors random-source) | procedure |
This procedure returns a procedure for generating pseudo random +u8vectors using the random source object random-source. The +returned procedure accepts a single parameter n, a nonnegative +exact integer, and returns a u8vector of length n containing +pseudo random exact integers in the range 0 to 255. +
+For example: +
+> (define rs (make-random-source)) +> (define rv (random-source-make-u8vectors rs)) +> (rv 10) +#u8(200 53 29 202 3 85 208 187 73 219) +> (rv 10) +#u8(113 8 182 120 138 103 53 192 40 176) + |
(random-source-make-f64vectors random-source [precision]) | procedure |
This procedure returns a procedure for generating pseudo random +f64vectors using the random source object random-source. The +returned procedure accepts a single parameter n, a nonnegative +exact integer, and returns an f64vector of length n containing +pseudo random inexact reals between, but not including, 0 and 1. +The optional parameter precision specifies an upper bound on the +minimum amount by which two generated pseudo-random numbers can be separated. +
+For example: +
+> (define rs (make-random-source)) +> (define rv (random-source-make-f64vectors rs)) +> (rv 3) +#f64(.7342236104231586 .2876463473845367 .8574025375628211) +> (rv 3) +#f64(.013863292728449427 .33449296573515447 .8162050798467028) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
Homogeneous vectors are vectors containing raw numbers of the same +type (signed or unsigned exact integers or inexact reals). There are +10 types of homogeneous vectors: +s8vector (vector of exact integers in the range -2^7 to 2^7-1), +u8vector (vector of exact integers in the range 0 to 2^8-1), +s16vector (vector of exact integers in the range -2^15 to 2^15-1), +u16vector (vector of exact integers in the range 0 to 2^16-1), +s32vector (vector of exact integers in the range -2^31 to 2^31-1), +u32vector (vector of exact integers in the range 0 to 2^32-1), +s64vector (vector of exact integers in the range -2^63 to 2^63-1), +u64vector (vector of exact integers in the range 0 to 2^64-1), +f32vector (vector of 32 bit floating point numbers), +and f64vector (vector of 64 bit floating point numbers). +
+The lexical syntax of homogeneous vectors is specified in +Homogeneous vector syntax. +
+The procedures available for homogeneous vectors, listed below, are +the analog of the normal vector/string procedures for each of the +homogeneous vector types. +
+ (s8vector? obj) | procedure |
(make-s8vector k [fill]) | procedure |
(s8vector exact-int8…) | procedure |
(s8vector-length s8vector) | procedure |
(s8vector-ref s8vector k) | procedure |
(s8vector-set! s8vector k exact-int8) | procedure |
(s8vector->list s8vector) | procedure |
(list->s8vector list-of-exact-int8) | procedure |
(s8vector-fill! s8vector fill) | procedure |
(subs8vector-fill! vector start end fill) | procedure |
(append-s8vectors lst) | procedure |
(s8vector-copy s8vector) | procedure |
(s8vector-append s8vector…) | procedure |
(subs8vector s8vector start end) | procedure |
(subs8vector-move! src-s8vector src-start src-end dst-s8vector dst-start) | procedure |
(s8vector-shrink! s8vector k) | procedure |
(u8vector? obj) | procedure |
(make-u8vector k [fill]) | procedure |
(u8vector exact-int8…) | procedure |
(u8vector-length u8vector) | procedure |
(u8vector-ref u8vector k) | procedure |
(u8vector-set! u8vector k exact-int8) | procedure |
(u8vector->list u8vector) | procedure |
(list->u8vector list-of-exact-int8) | procedure |
(u8vector-fill! u8vector fill) | procedure |
(subu8vector-fill! vector start end fill) | procedure |
(append-u8vectors lst) | procedure |
(u8vector-copy u8vector) | procedure |
(u8vector-append u8vector…) | procedure |
(subu8vector u8vector start end) | procedure |
(subu8vector-move! src-u8vector src-start src-end dst-u8vector dst-start) | procedure |
(u8vector-shrink! u8vector k) | procedure |
(s16vector? obj) | procedure |
(make-s16vector k [fill]) | procedure |
(s16vector exact-int16…) | procedure |
(s16vector-length s16vector) | procedure |
(s16vector-ref s16vector k) | procedure |
(s16vector-set! s16vector k exact-int16) | procedure |
(s16vector->list s16vector) | procedure |
(list->s16vector list-of-exact-int16) | procedure |
(s16vector-fill! s16vector fill) | procedure |
(subs16vector-fill! vector start end fill) | procedure |
(append-s16vectors lst) | procedure |
(s16vector-copy s16vector) | procedure |
(s16vector-append s16vector…) | procedure |
(subs16vector s16vector start end) | procedure |
(subs16vector-move! src-s16vector src-start src-end dst-s16vector dst-start) | procedure |
(s16vector-shrink! s16vector k) | procedure |
(u16vector? obj) | procedure |
(make-u16vector k [fill]) | procedure |
(u16vector exact-int16…) | procedure |
(u16vector-length u16vector) | procedure |
(u16vector-ref u16vector k) | procedure |
(u16vector-set! u16vector k exact-int16) | procedure |
(u16vector->list u16vector) | procedure |
(list->u16vector list-of-exact-int16) | procedure |
(u16vector-fill! u16vector fill) | procedure |
(subu16vector-fill! vector start end fill) | procedure |
(append-u16vectors lst) | procedure |
(u16vector-copy u16vector) | procedure |
(u16vector-append u16vector…) | procedure |
(subu16vector u16vector start end) | procedure |
(subu16vector-move! src-u16vector src-start src-end dst-u16vector dst-start) | procedure |
(u16vector-shrink! u16vector k) | procedure |
(s32vector? obj) | procedure |
(make-s32vector k [fill]) | procedure |
(s32vector exact-int32…) | procedure |
(s32vector-length s32vector) | procedure |
(s32vector-ref s32vector k) | procedure |
(s32vector-set! s32vector k exact-int32) | procedure |
(s32vector->list s32vector) | procedure |
(list->s32vector list-of-exact-int32) | procedure |
(s32vector-fill! s32vector fill) | procedure |
(subs32vector-fill! vector start end fill) | procedure |
(append-s32vectors lst) | procedure |
(s32vector-copy s32vector) | procedure |
(s32vector-append s32vector…) | procedure |
(subs32vector s32vector start end) | procedure |
(subs32vector-move! src-s32vector src-start src-end dst-s32vector dst-start) | procedure |
(s32vector-shrink! s32vector k) | procedure |
(u32vector? obj) | procedure |
(make-u32vector k [fill]) | procedure |
(u32vector exact-int32…) | procedure |
(u32vector-length u32vector) | procedure |
(u32vector-ref u32vector k) | procedure |
(u32vector-set! u32vector k exact-int32) | procedure |
(u32vector->list u32vector) | procedure |
(list->u32vector list-of-exact-int32) | procedure |
(u32vector-fill! u32vector fill) | procedure |
(subu32vector-fill! vector start end fill) | procedure |
(append-u32vectors lst) | procedure |
(u32vector-copy u32vector) | procedure |
(u32vector-append u32vector…) | procedure |
(subu32vector u32vector start end) | procedure |
(subu32vector-move! src-u32vector src-start src-end dst-u32vector dst-start) | procedure |
(u32vector-shrink! u32vector k) | procedure |
(s64vector? obj) | procedure |
(make-s64vector k [fill]) | procedure |
(s64vector exact-int64…) | procedure |
(s64vector-length s64vector) | procedure |
(s64vector-ref s64vector k) | procedure |
(s64vector-set! s64vector k exact-int64) | procedure |
(s64vector->list s64vector) | procedure |
(list->s64vector list-of-exact-int64) | procedure |
(s64vector-fill! s64vector fill) | procedure |
(subs64vector-fill! vector start end fill) | procedure |
(append-s64vectors lst) | procedure |
(s64vector-copy s64vector) | procedure |
(s64vector-append s64vector…) | procedure |
(subs64vector s64vector start end) | procedure |
(subs64vector-move! src-s64vector src-start src-end dst-s64vector dst-start) | procedure |
(s64vector-shrink! s64vector k) | procedure |
(u64vector? obj) | procedure |
(make-u64vector k [fill]) | procedure |
(u64vector exact-int64…) | procedure |
(u64vector-length u64vector) | procedure |
(u64vector-ref u64vector k) | procedure |
(u64vector-set! u64vector k exact-int64) | procedure |
(u64vector->list u64vector) | procedure |
(list->u64vector list-of-exact-int64) | procedure |
(u64vector-fill! u64vector fill) | procedure |
(subu64vector-fill! vector start end fill) | procedure |
(append-u64vectors lst) | procedure |
(u64vector-copy u64vector) | procedure |
(u64vector-append u64vector…) | procedure |
(subu64vector u64vector start end) | procedure |
(subu64vector-move! src-u64vector src-start src-end dst-u64vector dst-start) | procedure |
(u64vector-shrink! u64vector k) | procedure |
(f32vector? obj) | procedure |
(make-f32vector k [fill]) | procedure |
(f32vector inexact-real…) | procedure |
(f32vector-length f32vector) | procedure |
(f32vector-ref f32vector k) | procedure |
(f32vector-set! f32vector k inexact-real) | procedure |
(f32vector->list f32vector) | procedure |
(list->f32vector list-of-inexact-real) | procedure |
(f32vector-fill! f32vector fill) | procedure |
(subf32vector-fill! vector start end fill) | procedure |
(append-f32vectors lst) | procedure |
(f32vector-copy f32vector) | procedure |
(f32vector-append f32vector…) | procedure |
(subf32vector f32vector start end) | procedure |
(subf32vector-move! src-f32vector src-start src-end dst-f32vector dst-start) | procedure |
(f32vector-shrink! f32vector k) | procedure |
(f64vector? obj) | procedure |
(make-f64vector k [fill]) | procedure |
(f64vector inexact-real…) | procedure |
(f64vector-length f64vector) | procedure |
(f64vector-ref f64vector k) | procedure |
(f64vector-set! f64vector k inexact-real) | procedure |
(f64vector->list f64vector) | procedure |
(list->f64vector list-of-inexact-real) | procedure |
(f64vector-fill! f64vector fill) | procedure |
(subf64vector-fill! vector start end fill) | procedure |
(append-f64vectors lst) | procedure |
(f64vector-copy f64vector) | procedure |
(f64vector-append f64vector…) | procedure |
(subf64vector f64vector start end) | procedure |
(subf64vector-move! src-f64vector src-start src-end dst-f64vector dst-start) | procedure |
(f64vector-shrink! f64vector k) | procedure |
For example: +
+> (define v (u8vector 10 255 13)) +> (u8vector-set! v 2 99) +> v +#u8(10 255 99) +> (u8vector-ref v 1) +255 +> (u8vector->list v) +(10 255 99) +> (u8vector-shrink! v 2) +> (v) +#u8(10 255) + |
(object->u8vector obj [encoder]) | procedure |
(u8vector->object u8vector [decoder]) | procedure |
The procedure object->u8vector returns a u8vector that contains
+the sequence of bytes that encodes the object obj. The
+procedure u8vector->object decodes the sequence of bytes
+contained in the u8vector u8vector, which was produced by the
+procedure object->u8vector, and reconstructs an object
+structurally equal to the original object. In other words the
+procedures object->u8vector and u8vector->object
+respectively perform serialization and deserialization of Scheme
+objects. Note that some objects are non-serializable (e.g. threads,
+wills, some types of ports, and any object containing a
+non-serializable object).
+
The optional encoder and decoder parameters are single +parameter procedures which default to the identity function. The +encoder procedure is called during serialization. As the +serializer walks through obj, it calls the encoder +procedure on each sub-object X that is encountered. The +encoder transforms the object X into an object Y +that will be serialized instead of X. Similarly the +decoder procedure is called during deserialization. When an +object Y is encountered, the decoder procedure is called +to transform it into the object X that is the result of +deserialization. +
+The encoder and decoder procedures are useful to customize
+the serialized representation of objects. In particular, it can be
+used to define the semantics of serializing objects, such as threads
+and ports, that would otherwise not be serializable. The
+decoder procedure is typically the inverse of the encoder
+procedure, i.e. (decoder (encoder X)) =
+X.
+
For example: +
+> (define (make-adder x) (lambda (y) (+ x y))) +> (define f (make-adder 10)) +> (define a (object->u8vector f)) +> (define b (u8vector->object a)) +> (u8vector-length a) +1639 +> (f 5) +15 +> (b 5) +15 +> (pp b) +(lambda (y) (+ x y)) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
| 11.1 Hashing | ||
| 11.2 Weak references |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(object->serial-number obj) | procedure |
(serial-number->object n [default]) | procedure |
All Scheme objects are uniquely identified with a serial number which
+is a nonnegative exact integer. The object->serial-number procedure
+returns the serial number of object obj. This serial number is
+only allocated the first time the object->serial-number
+procedure is called on that object. Objects which do not have an
+external textual representation that can be read by the read
+procedure, use an external textual representation that includes a
+serial number of the form #n. Consequently, the
+procedures write, pretty-print, etc will call the
+object->serial-number procedure to get the serial number, and
+this may cause the serial number to be allocated.
+
The serial-number->object procedure takes an exact integer
+parameter n and returns the object whose serial number is
+n. If no object currently exists with that serial number,
+default is returned if it is specified, otherwise an
+unbound-serial-number-exception object is raised. The reader defines
+the following abbreviation for calling serial-number->object:
+the syntax #n, where n is a sequence of decimal
+digits and it is not followed by = or #,
+is equivalent to the list (serial-number->object n).
+
For example: +
+> (define z (list (lambda (x) (* x x)) (lambda (y) (/ 1 y)))) +> z +(#<procedure #2> #<procedure #3>) +> (#3 10) +1/10 +> '(#3 10) +((serial-number->object 3) 10) +> car +#<procedure #4 car> +> (#4 z) +#<procedure #2> + |
(unbound-serial-number-exception? obj) | procedure |
(unbound-serial-number-exception-procedure exc) | procedure |
(unbound-serial-number-exception-arguments exc) | procedure |
Unbound-serial-number-exception objects are raised by the procedure
+serial-number->object when no object currently exists with that
+serial number. The parameter exc must be an
+unbound-serial-number-exception object.
+
The procedure unbound-serial-number-exception? returns
+#t when obj is a unbound-serial-number-exception
+object and #f otherwise.
+
The procedure unbound-serial-number-exception-procedure
+returns the procedure that raised exc.
+
The procedure unbound-serial-number-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
For example: +
+> (define (handler exc) + (if (unbound-serial-number-exception? exc) + (list (unbound-serial-number-exception-procedure exc) + (unbound-serial-number-exception-arguments exc)) + 'not-unbound-serial-number-exception)) +> (with-exception-catcher + handler + (lambda () (serial-number->object 1000))) +(#<procedure #2 serial-number->object> (1000)) + |
(symbol-hash symbol) | procedure |
The symbol-hash procedure returns the hash number of the symbol
+symbol. The hash number is a small exact integer (fixnum).
+When symbol is an interned symbol the value returned is the same
+as (string=?-hash (symbol->string symbol)).
+
For example: +
+> (symbol-hash 'car) +444471047 + |
(keyword-hash keyword) | procedure |
The keyword-hash procedure returns the hash number of the
+keyword keyword. The hash number is a small exact integer
+(fixnum). When keyword is an interned keyword the value
+returned is the same as (string=?-hash (keyword->string
+keyword)).
+
For example: +
+> (keyword-hash car:) +444471047 + |
(string=?-hash string) | procedure |
The string=?-hash procedure returns the hash number of the
+string string. The hash number is a small exact integer
+(fixnum). For any two strings s1 and s2, (string=?
+s1 s2) implies (= (string=?-hash s1)
+(string=?-hash s2)).
+
For example: +
+> (string=?-hash "car") +444471047 + |
(string-ci=?-hash string) | procedure |
The string-ci=?-hash procedure returns the hash number of the
+string string. The hash number is a small exact integer
+(fixnum). For any two strings s1 and s2, (string-ci=?
+s1 s2) implies (= (string-ci=?-hash s1)
+(string-ci=?-hash s2)).
+
For example: +
+> (string-ci=?-hash "CaR") +444471047 + |
(eq?-hash obj) | procedure |
The eq?-hash procedure returns the hash number of the object
+obj. The hash number is a small exact integer (fixnum). For
+any two objects o1 and o2, (eq? o1 o2)
+implies (= (eq?-hash o1) (eq?-hash o2)).
+
For example: +
+> (eq?-hash #t) +536870910 + |
(eqv?-hash obj) | procedure |
The eqv?-hash procedure returns the hash number of the object
+obj. The hash number is a small exact integer (fixnum). For
+any two objects o1 and o2, (eqv? o1 o2)
+implies (= (eqv?-hash o1) (eqv?-hash o2)).
+
For example: +
+> (eqv?-hash 1.5) +496387656 + |
(equal?-hash obj) | procedure |
The equal?-hash procedure returns the hash number of the object
+obj. The hash number is a small exact integer (fixnum). For
+any two objects o1 and o2, (equal? o1 o2)
+implies (= (equal?-hash o1) (equal?-hash o2)).
+
For example: +
+> (equal?-hash (list 1 2 3)) +442438567 + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The garbage collector is responsible for reclaiming objects that are +no longer needed by the program. This is done by analyzing the +reachability graph of all objects from the roots (i.e. the global +variables, the runnable threads, permanently allocated objects such as +procedures defined in a compiled file, nonexecutable wills, etc). If +a root or a reachable object X contains a reference to an object +Y then Y is reachable. As a general rule, unreachable +objects are reclaimed by the garbage collector. +
+There are two types of references: strong references and weak +references. Most objects, including pairs, vectors, records and +closures, contain strong references. An object X is +strongly reachable if there is a path from the roots to X +that traverses only strong references. Weak references only occur in +wills and tables. There are two types of weak references: will-weak +references and table-weak references. If all paths from the roots to +an object Y traverse at least one table-weak reference, then +Y will be reclaimed by the garbage collector. The will-weak +references are used for finalization and are explained in the next +section. +
+| 11.2.1 Wills | ||
| 11.2.2 Tables |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The following procedures implement the will data type. Will +objects provide support for finalization. A will is an object that +contains a will-weak reference to a testator object (the object +attached to the will), and a strong reference to an action +procedure which is a one parameter procedure which is called when the +will is executed. +
+ (make-will testator action) | procedure |
(will? obj) | procedure |
(will-testator will) | procedure |
(will-execute! will) | procedure |
The make-will procedure creates a will object with the given
+testator object and action procedure. The will?
+procedure tests if obj is a will object. The
+will-testator procedure gets the testator object attached to
+the will. The will-execute! procedure executes
+will.
+
A will becomes executable when its testator object is not +strongly reachable (i.e. the testator object is either +unreachable or only reachable using paths from the roots that traverse +at least one weak reference). Some objects, including symbols, small +exact integers (fixnums), booleans and characters, are considered to +be always strongly reachable. +
+When the runtime system detects that a will has become executable the
+current computation is interrupted, the will’s testator is set to
+#f and the will’s action procedure is called with the will’s
+testator as the sole argument. Currently only the garbage collector
+detects when wills become executable but this may change in future
+versions of Gambit (for example the compiler could perform an analysis
+to infer will executability at compile time). The garbage collector
+builds a list of all executable wills. Shortly after a garbage
+collection, the action procedures of these wills will be called. The
+link from the will to the action procedure is severed when the action
+procedure is called.
+
Note that the testator object will not be reclaimed during the garbage +collection that determined executability of the will. It is only when +an object is not reachable from the roots that it is reclaimed by the +garbage collector. +
+A remarkable feature of wills is that an action procedure can +“resurrect” an object. An action procedure could for example assign +the testator object to a global variable or create a new will with the +same testator object. +
+For example: +
+> (define a (list 123))
+> (set-cdr! a a) ; create a circular list
+> (define b (vector a))
+> (define c #f)
+> (define w
+ (let ((obj a))
+ (make-will obj
+ (lambda (x) ; x will be eq? to obj
+ (display "executing action procedure")
+ (newline)
+ (set! c x)))))
+> (will? w)
+#t
+> (car (will-testator w))
+123
+> (##gc)
+> (set! a #f)
+> (##gc)
+> (set! b #f)
+> (##gc)
+executing action procedure
+> (will-testator w)
+#f
+> (car c)
+123
+ |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The following procedures implement the table data type. Tables +are heterogenous structures whose elements are indexed by keys which +are arbitrary objects. Tables are similar to association lists but +are abstract and the access time for large tables is typically smaller. +Each key contained in the table is bound to a value. The length of +the table is the number of key/value bindings it contains. New +key/value bindings can be added to a table, the value bound to a key +can be changed, and existing key/value bindings can be removed. +
+The references to the keys can either be all strong or all table-weak +and the references to the values can either be all strong or all +table-weak. The garbage collector removes key/value bindings from a +table when 1) the key is a table-weak reference and the key is +unreachable or only reachable using paths from the roots that traverse +at least one table-weak reference, or 2) the value is a table-weak +reference and the value is unreachable or only reachable using paths +from the roots that traverse at least one table-weak reference. +Key/value bindings that are removed by the garbage collector are +reclaimed immediately. +
+Although there are several possible ways of implementing tables, the +current implementation uses hashing with open-addressing. This is +space efficient and provides constant-time access. Hash tables are +automatically resized to maintain the load within specified bounds. +The load is the number of active entries (the length of the table) +divided by the total number of entries in the hash table. +
+Tables are parameterized with a key comparison procedure. By default
+the equal? procedure is used, but eq?, eqv?,
+string=?, string-ci=?, or a user defined procedure can
+also be used. To support arbitrary key comparison procedures, tables
+are also parameterized with a hashing procedure accepting a key as its
+single parameter and returning a fixnum result. The hashing procedure
+hash must be consistent with the key comparison procedure
+test, that is, for any two keys k1 and k2 in the
+table, (test k1 k2) implies (=
+(hash k1) (hash k2)). A default hashing
+procedure consistent with the key comparison procedure is provided by
+the system. The default hashing procedure generally gives good
+performance when the key comparison procedure is eq?,
+eqv?, equal?, string=?, and string-ci=?.
+However, for user defined key comparison procedures, the default
+hashing procedure always returns 0. This degrades the performance of
+the table to a linear search.
+
Tables can be compared for equality using the equal? procedure.
+Two tables X and Y are considered equal by
+equal? when they have the same weakness attributes, the same
+key comparison procedure, the same hashing procedure, the same length,
+and for all the keys k in X, (equal?
+(table-ref X k) (table-ref Y k)).
+
(make-table [size: size] [init: init] [weak-keys: weak-keys] [weak-values: weak-values] [test: test] [hash: hash] [min-load: min-load] [max-load: max-load]) | procedure |
The procedure make-table returns a new table. The optional keyword
+parameters specify various parameters of the table.
+
The size parameter is a nonnegative exact integer indicating +the expected length of the table. The system uses size to +choose an appropriate initial size of the hash table so that it does not +need to be resized too often. +
+The init parameter indicates a value that is associated to keys +that are not in the table. When init is not specified, no value +is associated to keys that are not in the table. +
+The weak-keys and weak-values parameters are extended +booleans indicating respectively whether the keys and values are +table-weak references (true) or strong references (false). By default +the keys and values are strong references. +
+The test parameter indicates the key comparison procedure. The
+default key comparison procedure is equal?. The key comparison
+procedures eq?, eqv?, equal?, string=?,
+and string-ci=? are special because the system will use a
+reasonably good hash procedure when none is specified.
+
The hash parameter indicates the hash procedure. This procedure
+must accept a single key parameter, return a fixnum, and be consistent
+with the key comparison procedure. When hash is not specified, a
+default hash procedure is used. The default hash procedure is
+reasonably good when the key comparison procedure is eq?,
+eqv?, equal?, string=?, or string-ci=?.
+
The min-load and max-load parameters are real numbers that +indicate the minimum and maximum load of the table respectively. The +table is resized when adding or deleting a key/value binding would +bring the table’s load outside of this range. The min-load +parameter must be no less than 0.05 and the max-load parameter +must be no greater than 0.95. Moreover the difference between +min-load and max-load must be at least 0.20. When +min-load is not specified, the value 0.45 is used. When +max-load is not specified, the value 0.90 is used. +
+For example: +
+> (define t (make-table)) +> (table? t) +#t +> (table-length t) +0 +> (table-set! t (list 1 2) 3) +> (table-set! t (list 4 5) 6) +> (table-ref t (list 1 2)) +3 +> (table-length t) +2 + |
(table? obj) | procedure |
The procedure table? returns #t when obj is a
+table and #f otherwise.
+
For example: +
+> (table? (make-table)) +#t +> (table? 123) +#f + |
(table-length table) | procedure |
The procedure table-length returns the number of key/value
+bindings contained in the table table.
+
For example: +
+> (define t (make-table weak-keys: #t)) +> (define x (list 1 2)) +> (define y (list 3 4)) +> (table-set! t x 111) +> (table-set! t y 222) +> (table-length t) +2 +> (table-set! t x) +> (table-length t) +1 +> (##gc) +> (table-length t) +1 +> (set! y #f) +> (##gc) +> (table-length t) +0 + |
(table-ref table key [default]) | procedure |
The procedure table-ref returns the value bound to the object
+key in the table table. When key is not bound and
+default is specified, default is returned. When
+default is not specified but an init parameter was
+specified when table was created, init is returned.
+Otherwise an unbound-table-key-exception object is raised.
+
For example: +
+> (define t1 (make-table init: 999)) +> (table-set! t1 (list 1 2) 3) +> (table-ref t1 (list 1 2)) +3 +> (table-ref t1 (list 4 5)) +999 +> (table-ref t1 (list 4 5) #f) +#f +> (define t2 (make-table)) +> (table-ref t2 (list 4 5)) +*** ERROR IN (console)@7.1 -- Unbound table key +(table-ref '#<table #2> '(4 5)) + |
(table-set! table key [value]) | procedure |
The procedure table-set! binds the object key to
+value in the table table. When value is not
+specified, if table contains a binding for key then the
+binding is removed from table. The procedure table-set!
+returns an unspecified value.
+
For example: +
+> (define t (make-table)) +> (table-set! t (list 1 2) 3) +> (table-set! t (list 4 5) 6) +> (table-set! t (list 4 5)) +> (table-set! t (list 7 8)) +> (table-ref t (list 1 2)) +3 +> (table-ref t (list 4 5)) +*** ERROR IN (console)@7.1 -- Unbound table key +(table-ref '#<table #2> '(4 5)) + |
(table-search proc table) | procedure |
The procedure table-search searches the table table for a
+key/value binding for which the two parameter procedure proc
+returns a non false result. For each key/value binding visited by
+table-search the procedure proc is called with the key as
+the first parameter and the value as the second parameter. The
+procedure table-search returns the first non false value
+returned by proc, or #f if proc returned #f
+for all key/value bindings in table.
+
The order in which the key/value bindings are visited is unspecified
+and may vary from one call of table-search to the next. While
+a call to table-search is being performed on table, it is
+an error to call any of the following procedures on table:
+table-ref, table-set!, table-search,
+table-for-each, table-copy, table-merge,
+table-merge!, and table->list. It is also an error to
+compare with equal? (directly or indirectly with member,
+assoc, table-ref, etc.) an object that contains
+table. All these procedures may cause table to be
+reordered and resized. This restriction allows a more efficient
+iteration over the key/value bindings.
+
For example: +
+> (define square (make-table)) +> (table-set! square 2 4) +> (table-set! square 3 9) +> (table-search (lambda (k v) (and (odd? k) v)) square) +9 + |
(table-for-each proc table) | procedure |
The procedure table-for-each calls the two parameter procedure
+proc for each key/value binding in the table table. The
+procedure proc is called with the key as the first parameter and
+the value as the second parameter. The procedure table-for-each
+returns an unspecified value.
+
The order in which the key/value bindings are visited is unspecified
+and may vary from one call of table-for-each to the next.
+While a call to table-for-each is being performed on
+table, it is an error to call any of the following procedures on
+table: table-ref, table-set!, table-search,
+table-for-each, and table->list. It is also an error to
+compare with equal? (directly or indirectly with member,
+assoc, table-ref, etc.) an object that contains
+table. All these procedures may cause table to be
+reordered and resized. This restriction allows a more efficient
+iteration over the key/value bindings.
+
For example: +
+> (define square (make-table)) +> (table-set! square 2 4) +> (table-set! square 3 9) +> (table-for-each (lambda (k v) (write (list k v)) (newline)) square) +(2 4) +(3 9) + |
(table->list table) | procedure |
The procedure table->list returns an association list
+containing the key/value bindings in the table table. Each
+key/value binding yields a pair whose car field is the key and whose
+cdr field is the value bound to that key. The order of the bindings
+in the list is unspecified.
+
For example: +
+> (define square (make-table)) +> (table-set! square 2 4) +> (table-set! square 3 9) +> (table->list square) +((3 . 9) (2 . 4)) + |
(list->table list [size: size] [init: init] [weak-keys: weak-keys] [weak-values: weak-values] [test: test] [hash: hash] [min-load: min-load] [max-load: max-load]) | procedure |
The procedure list->table returns a new table containing the
+key/value bindings in the association list list. The optional
+keyword parameters specify various parameters of the table and have
+the same meaning as for the make-table procedure.
+
Each element of list is a pair whose car field is a key and +whose cdr field is the value bound to that key. If a key appears more +than once in list (tested using the table’s key comparison +procedure) it is the first key/value binding in list that has +precedence. +
+For example: +
+> (define t (list->table '((b . 2) (a . 1) (c . 3) (a . 4)))) +> (table->list t) +((a . 1) (b . 2) (c . 3)) + |
(unbound-table-key-exception? obj) | procedure |
(unbound-table-key-exception-procedure exc) | procedure |
(unbound-table-key-exception-arguments exc) | procedure |
Unbound-table-key-exception objects are raised by the procedure
+table-ref when the key does not have a binding in the table.
+The parameter exc must be an unbound-table-key-exception object.
+
The procedure unbound-table-key-exception? returns
+#t when obj is a unbound-table-key-exception
+object and #f otherwise.
+
The procedure unbound-table-key-exception-procedure
+returns the procedure that raised exc.
+
The procedure unbound-table-key-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
For example: +
+> (define t (make-table)) +> (define (handler exc) + (if (unbound-table-key-exception? exc) + (list (unbound-table-key-exception-procedure exc) + (unbound-table-key-exception-arguments exc)) + 'not-unbound-table-key-exception)) +> (with-exception-catcher + handler + (lambda () (table-ref t '(1 2)))) +(#<procedure #2 table-ref> (#<table #3> (1 2))) + |
(table-copy table) | procedure |
The procedure table-copy returns a new table containing the
+same key/value bindings as table and the same table parameters
+(i.e. hash procedure, key comparison procedure, key and value
+weakness, etc).
+
For example: +
+> (define t (list->table '((b . 2) (a . 1) (c . 3)))) +> (define x (table-copy t)) +> (table-set! t 'b 99) +> (table->list t) +((a . 1) (b . 99) (c . 3)) +> (table->list x) +((a . 1) (b . 2) (c . 3)) + |
(table-merge! table1 table2 [table2-takes-precedence?]) | procedure |
The procedure table-merge! returns table1 after the
+key/value bindings contained in table2 have been added to it.
+When a key exists both in table1 and table2, then the
+parameter table2-takes-precedence? indicates which binding will
+be kept (the one in table1 if table2-takes-precedence? is
+false, and the one in table2 otherwise). If
+table2-takes-precedence? is not specified the binding in
+table1 is kept.
+
For example: +
+> (define t1 (list->table '((a . 1) (b . 2) (c . 3)))) +> (define t2 (list->table '((a . 4) (b . 5) (z . 6)))) +> (table->list (table-merge! t1 t2)) +((a . 1) (b . 2) (c . 3) (z . 6)) +> (define t1 (list->table '((a . 1) (b . 2) (c . 3)))) +> (define t2 (list->table '((a . 4) (b . 5) (z . 6)))) +> (table->list (table-merge! t1 t2 #t)) +((a . 4) (b . 5) (c . 3) (z . 6)) + |
(table-merge table1 table2 [table2-takes-precedence?]) | procedure |
The procedure table-merge returns a copy of table1
+(created with table-copy) to which the key/value bindings
+contained in table2 have been added using table-merge!.
+When a key exists both in table1 and table2, then the
+parameter table2-takes-precedence? indicates which binding will
+be kept (the one in table1 if table2-takes-precedence? is
+false, and the one in table2 otherwise). If
+table2-takes-precedence? is not specified the binding in
+table1 is kept.
+
For example: +
+> (define t1 (list->table '((a . 1) (b . 2) (c . 3)))) +> (define t2 (list->table '((a . 4) (b . 5) (z . 6)))) +> (table->list (table-merge t1 t2)) +((a . 1) (b . 2) (c . 3) (z . 6)) +> (table->list (table-merge t1 t2 #t)) +((a . 4) (b . 5) (c . 3) (z . 6)) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(define-structure name field…) | special form |
Record data types similar to Pascal records and C struct
+types can be defined using the define-structure special form.
+The identifier name specifies the name of the new data type. The
+structure name is followed by k identifiers naming each field of
+the record. The define-structure expands into a set of definitions
+of the following procedures:
+
Record data types have a printed representation that includes the name
+of the type and the name and value of each field. Record data types
+can not be read by the read procedure.
+
For example: +
+> (define-structure point x y color) +> (define p (make-point 3 5 'red)) +> p +#<point #2 x: 3 y: 5 color: red> +> (point-x p) +3 +> (point-color p) +red +> (point-color-set! p 'black) +> p +#<point #2 x: 3 y: 5 color: black> + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
Gambit supports the execution of multiple Scheme threads. These +threads are managed entirely by Gambit’s runtime and are not related +to the host operating system’s threads. Gambit’s runtime does not +currently take advantage of multiprocessors (i.e. at most one thread is +running). +
+| 13.1 Introduction | ||
| 13.2 Thread objects | ||
| 13.3 Mutex objects | ||
| 13.4 Condition variable objects | ||
| 13.5 Fairness | ||
| 13.6 Memory coherency | ||
| 13.7 Timeouts | ||
| 13.8 Primordial thread | ||
| 13.9 Procedures |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
Multithreading is a paradigm that is well suited for building complex +systems such as: servers, GUIs, and high-level operating systems. +Gambit’s thread system offers mechanisms for creating threads of +execution and for synchronizing them. The thread system also supports +features which are useful in a real-time context, such as priorities, +priority inheritance and timeouts. +
+The thread system provides the following data types: +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
A running thread is a thread that is currently executing. A
+runnable thread is a thread that is ready to execute or running.
+A thread is blocked if it is waiting for a mutex to become
+unlocked, an I/O operation to become possible, the end of a “sleep”
+period, etc. A new thread is a thread that has been allocated
+but has not yet been initialized. An initialized thread is a
+thread that can be made runnable. A new thread becomes runnable when
+it is started by calling thread-start!. A terminated
+thread is a thread that can no longer become runnable (but
+deadlocked threads are not considered terminated). The only
+valid transitions between the thread states are from new to
+initialized, from initialized to runnable, between runnable and
+blocked, and from any state except new to terminated as indicated in
+the following diagram:
+
unblock + start <------- +NEW -------> INITIALIZED -------> RUNNABLE -------> BLOCKED + \ | block / + \ v / + +-----> TERMINATED <----+ + |
Each thread has a base priority, which is a real number (where a +higher numerical value means a higher priority), a priority boost, +which is a nonnegative real number representing the priority increase +applied to a thread when it blocks, and a quantum, which is a +nonnegative real number representing a duration in seconds. +
+Each thread has a specific field which can be used in an +application specific way to associate data with the thread (some thread +systems call this “thread local storage”). +
+Each thread has a mailbox which is used for inter-thread +communication. +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
A mutex can be in one of four states: locked (either owned +or not owned) and unlocked (either abandoned or +not abandoned). +
+An attempt to lock a mutex only succeeds if the mutex is in an unlocked +state, otherwise the current thread will wait. A mutex in the +locked/owned state has an associated owner thread, which by +convention is the thread that is responsible for unlocking the mutex +(this case is typical of critical sections implemented as “lock mutex, +perform operation, unlock mutex”). A mutex in the locked/not-owned +state is not linked to a particular thread. +
+A mutex becomes locked when a thread locks it using the +mutex-lock! primitive. A mutex becomes unlocked/abandoned when +the owner of a locked/owned mutex terminates. A mutex becomes +unlocked/not-abandoned when a thread unlocks it using the +mutex-unlock! primitive. +
+The mutex primitives do not implement recursive mutex semantics. +An attempt to lock a mutex that is locked implies that the current +thread waits even if the mutex is owned by the current thread (this can +lead to a deadlock if no other thread unlocks the mutex). +
+Each mutex has a specific field which can be used in an +application specific way to associate data with the mutex. +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
A condition variable represents a set of blocked threads. These blocked +threads are waiting for a certain condition to become true. When a +thread modifies some program state that might make the condition true, +the thread unblocks some number of threads (one or all depending on the +primitive used) so they can check if the condition is now true. This +allows complex forms of interthread synchronization to be expressed more +conveniently than with mutexes alone. +
+Each condition variable has a specific field which can be used in +an application specific way to associate data with the condition +variable. +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
In various situations the scheduler must select one thread from a set of +threads (e.g. which thread to run when a running thread blocks or +expires its quantum, which thread to unblock when a mutex becomes +unlocked or a condition variable is signaled). The constraints on the +selection process determine the scheduler’s fairness. The +selection depends on the order in which threads become runnable or +blocked and on the priority attached to the threads. +
+The definition of fairness requires the notion of time ordering, +i.e. “event A occured before event B”. For the purpose of +establishing time ordering, the scheduler uses a clock with a discrete, +usually variable, resolution (a “tick”). Events occuring in a given +tick can be considered to be simultaneous (i.e. if event A occured +before event B in real time, then the scheduler will claim that +event A occured before event B unless both events fall +within the same tick, in which case the scheduler arbitrarily chooses a +time ordering). +
+Each thread T has three priorities which affect fairness; the +base priority, the boosted priority, and the effective +priority. +
+Let P(T) be the effective priority of thread T and +let R(T) be the most recent time when one of the following +events occurred for thread T, thus making it runnable: T +was started by calling thread-start!, T called +thread-yield!, T expired its quantum, or T became +unblocked. Let the relation NL(T1,T2), “T1 +no later than T2”, be true if +P(T1)<P(T2) or +P(T1)=P(T2) and +R(T1)>R(T2), and false otherwise. The +scheduler will schedule the execution of threads in such a way that +whenever there is at least one runnable thread, 1) within a finite +time at least one thread will be running, and 2) there is never a pair +of runnable threads T1 and T2 for which +NL(T1,T2) is true and T1 is not running and +T2 is running. +
+A thread T expires its quantum when an amount of time equal to +T’s quantum has elapsed since T entered the running state +and T did not block, terminate or call thread-yield!. +At that point T exits the running state to allow other threads to +run. A thread’s quantum is thus an indication of the rate of progress +of the thread relative to the other threads of the same priority. +Moreover, the resolution of the timer measuring the running time may +cause a certain deviation from the quantum, so a thread’s quantum should +only be viewed as an approximation of the time it can run before +yielding to another thread. +
+Threads blocked on a given mutex or condition variable will unblock in +an order which is consistent with decreasing priority and increasing +blocking time (i.e. the highest priority thread unblocks first, and +among equal priority threads the one that blocked first unblocks first). +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
Read and write operations on the store (such as reading and writing a +variable, an element of a vector or a string) are not atomic. It is +an error for a thread to write a location in the store while some +other thread reads or writes that same location. It is the +responsibility of the application to avoid write/read and write/write +races through appropriate uses of the synchronization primitives. +
+Concurrent reads and writes to ports are allowed. It is the +responsibility of the implementation to serialize accesses to a given +port using the appropriate synchronization primitives. +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
All synchronization primitives which take a timeout parameter accept +three types of values as a timeout, with the following meaning: +
+When a timeout denotes the current time or a time in the past, the
+synchronization primitive claims that the timeout has been reached
+only after the other synchronization conditions have been checked.
+Moreover the thread remains running (it does not enter the blocked
+state). For example, (mutex-lock! m 0) will lock mutex
+m and return #t if m is
+currently unlocked, otherwise #f is returned because the
+timeout is reached.
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The execution of a program is initially under the control of a single +thread known as the primordial thread. The primordial thread has an +unspecified +base priority, priority boost, boosted flag, quantum, +name, specific field, dynamic environment, dynamic-wind +stack, and exception-handler. All threads are terminated when the +primordial thread terminates (normally or not). +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(current-thread) | procedure |
This procedure returns the current thread. For example: +
+> (current-thread) +#<thread #1 primordial> +> (eq? (current-thread) (current-thread)) +#t + |
(thread? obj) | procedure |
This procedure returns #t when obj is a thread object and
+#f otherwise.
+
For example: +
+> (thread? (current-thread)) +#t +> (thread? 'foo) +#f + |
(make-thread thunk [name [thread-group]]) | procedure |
(make-root-thread thunk [name [thread-group [input-port [output-port]]]]) | procedure |
The make-thread procedure creates and returns an initialized
+thread. This thread is not automatically made runnable (the procedure
+thread-start! must be used for this). A thread has the
+following fields: base priority, priority boost, boosted flag,
+quantum, name, specific, end-result, end-exception, and a list of
+locked/owned mutexes it owns. The thread’s execution consists of a
+call to thunk with the initial continuation. This
+continuation causes the (then) current thread to store the result in
+its end-result field, abandon all mutexes it owns, and finally
+terminate. The dynamic-wind stack of the initial continuation
+is empty. The optional name is an arbitrary Scheme object which
+identifies the thread (useful for debugging); it defaults to an
+unspecified value. The specific field is set to an unspecified value.
+The optional thread-group indicates which thread group this
+thread belongs to; it defaults to the thread group of the current
+thread. The base priority, priority boost, and quantum of the thread
+are set to the same value as the current thread and the boosted flag
+is set to false. The thread’s mailbox is initially empty. The thread
+inherits the dynamic environment from the current thread. Moreover, in
+this dynamic environment the exception-handler is bound to the
+initial exception-handler which is a unary procedure which
+causes the (then) current thread to store in its end-exception field
+an uncaught-exception object whose “reason” is the argument of the
+handler, abandon all mutexes it owns, and finally terminate.
+
The make-root-thread procedure behaves like the
+make-thread procedure except the created thread does not
+inherit the dynamic environment from the current thread and the base
+priority is set to 0, the priority boost is set to 1.0e-6, and the
+quantum is set to 0.02. The dynamic environment of the thread has the
+global bindings of the parameter objects, except
+current-input-port which is bound to input-port,
+current-output-port which is bound to output-port, and
+current-directory which is bound to the initial current working
+directory of the current process. If input-port is not
+specified it defaults to a port corresponding to the standard input
+(stdin). If output-port is not specified it defaults to
+a port corresponding to the standard output (stdout).
+
For example: +
+> (make-thread (lambda () (write 'hello))) +#<thread #2> +> (make-root-thread (lambda () (write 'world)) 'a-name) +#<thread #3 a-name> + |
(thread-name thread) | procedure |
This procedure returns the name of the thread. For example: +
+> (thread-name (make-thread (lambda () #f) 'foo)) +foo + |
(thread-specific thread) | procedure |
(thread-specific-set! thread obj) | procedure |
The thread-specific procedure returns the content of the
+thread’s specific field.
+
The thread-specific-set! procedure stores obj into the
+thread’s specific field and returns an unspecified value.
+
For example: +
+> (thread-specific-set! (current-thread) "hello") +> (thread-specific (current-thread)) +"hello" + |
(thread-base-priority thread) | procedure |
(thread-base-priority-set! thread priority) | procedure |
The procedure thread-base-priority returns a real number which
+corresponds to the base priority of the thread.
+
The procedure thread-base-priority-set! changes the base
+priority of the thread to priority and returns an
+unspecified value. The priority must be a real number.
+
For example: +
+> (thread-base-priority-set! (current-thread) 12.3) +> (thread-base-priority (current-thread)) +12.3 + |
(thread-priority-boost thread) | procedure |
(thread-priority-boost-set! thread priority-boost) | procedure |
The procedure thread-priority-boost returns a real number which
+corresponds to the priority boost of the thread.
+
The procedure thread-priority-boost-set! changes the priority
+boost of the thread to priority-boost and returns an
+unspecified value. The priority-boost must be a nonnegative
+real.
+
For example: +
+> (thread-priority-boost-set! (current-thread) 2.5) +> (thread-priority-boost (current-thread)) +2.5 + |
(thread-quantum thread) | procedure |
(thread-quantum-set! thread quantum) | procedure |
The procedure thread-quantum returns a real number which
+corresponds to the quantum of the thread.
+
The procedure thread-quantum-set! changes the quantum of the
+thread to quantum and returns an unspecified value. The
+quantum must be a nonnegative real. A value of zero selects the
+smallest quantum supported by the implementation.
+
For example: +
+> (thread-quantum-set! (current-thread) 1.5) +> (thread-quantum (current-thread)) +1.5 +> (thread-quantum-set! (current-thread) 0) +> (thread-quantum (current-thread)) +0. + |
(thread-start! thread) | procedure |
This procedure makes thread runnable and returns the +thread. The thread must be an initialized thread. +
+For example: +
+> (let ((t (thread-start! (make-thread (lambda () (write 'a))))))
+ (write 'b)
+ (thread-join! t))
+ab> or ba>
+ |
NOTE: It is useful to separate thread creation and thread activation
+to avoid the race condition that would occur if the created thread
+tries to examine a table in which the current thread stores the
+created thread. See the last example of the thread-terminate!
+procedure which contains mutually recursive threads.
+
(thread-yield!) | procedure |
This procedure causes the current thread to exit the running state as +if its quantum had expired and returns an unspecified value. +
+For example: +
+; a busy loop that avoids being too wasteful of the CPU + +(let loop () + (if (mutex-lock! m 0) ; try to lock m but don't block + (begin + (display "locked mutex m") + (mutex-unlock! m)) + (begin + (do-something-else) + (thread-yield!) ; relinquish rest of quantum + (loop)))) + |
(thread-sleep! timeout) | procedure |
This procedure causes the current thread to wait until the timeout is +reached and returns an unspecified value. This blocks the thread only +if timeout represents a point in the future. It is an error for +timeout to be #f. +
+For example: +
+; a clock with a gradual drift: + +(let loop ((x 1)) + (thread-sleep! 1) + (write x) + (loop (+ x 1))) + +; a clock with no drift: + +(let ((start (time->seconds (current-time))) + (let loop ((x 1)) + (thread-sleep! (seconds->time (+ x start))) + (write x) + (loop (+ x 1)))) + |
(thread-terminate! thread) | procedure |
This procedure causes an abnormal termination of the thread. If
+the thread is not already terminated, all mutexes owned by the
+thread become unlocked/abandoned and a
+terminated-thread-exception object is stored in the thread’s
+end-exception field. If thread is the current thread,
+thread-terminate! does not return. Otherwise
+thread-terminate! returns an unspecified value; the termination
+of the thread will occur at some point between the calling of
+thread-terminate! and a finite time in the future (an explicit
+thread synchronization is needed to detect termination, see
+thread-join!).
+
For example: +
+(define (amb thunk1 thunk2) + (let ((result #f) + (result-mutex (make-mutex)) + (done-mutex (make-mutex))) + (letrec ((child1 + (make-thread + (lambda () + (let ((x (thunk1))) + (mutex-lock! result-mutex #f #f) + (set! result x) + (thread-terminate! child2) + (mutex-unlock! done-mutex))))) + (child2 + (make-thread + (lambda () + (let ((x (thunk2))) + (mutex-lock! result-mutex #f #f) + (set! result x) + (thread-terminate! child1) + (mutex-unlock! done-mutex)))))) + (mutex-lock! done-mutex #f #f) + (thread-start! child1) + (thread-start! child2) + (mutex-lock! done-mutex #f #f) + result))) + |
NOTE: This operation must be used carefully because it terminates a +thread abruptly and it is impossible for that thread to perform any +kind of cleanup. This may be a problem if the thread is in the middle +of a critical section where some structure has been put in an +inconsistent state. However, another thread attempting to enter this +critical section will raise an abandoned-mutex-exception object +because the mutex is unlocked/abandoned. This helps avoid observing +an inconsistent state. Clean termination can be obtained by polling, +as shown in the example below. +
+For example: +
+(define (spawn thunk) + (let ((t (make-thread thunk))) + (thread-specific-set! t #t) + (thread-start! t) + t)) + +(define (stop! thread) + (thread-specific-set! thread #f) + (thread-join! thread)) + +(define (keep-going?) + (thread-specific (current-thread))) + +(define count! + (let ((m (make-mutex)) + (i 0)) + (lambda () + (mutex-lock! m) + (let ((x (+ i 1))) + (set! i x) + (mutex-unlock! m) + x)))) + +(define (increment-forever!) + (let loop () (count!) (if (keep-going?) (loop)))) + +(let ((t1 (spawn increment-forever!)) + (t2 (spawn increment-forever!))) + (thread-sleep! 1) + (stop! t1) + (stop! t2) + (count!)) ==> 377290 + |
(thread-join! thread [timeout [timeout-val]]) | procedure |
This procedure causes the current thread to wait until the +thread terminates (normally or not) or until the timeout is +reached if timeout is supplied. If the timeout is reached, +thread-join! returns timeout-val if it is supplied, +otherwise a join-timeout-exception object is raised. If the +thread terminated normally, the content of the end-result field +is returned, otherwise the content of the end-exception field is +raised. +
+For example: +
+(let ((t (thread-start! (make-thread (lambda () (expt 2 100)))))) + (do-something-else) + (thread-join! t)) ==> 1267650600228229401496703205376 + +(let ((t (thread-start! (make-thread (lambda () (raise 123)))))) + (do-something-else) + (with-exception-handler + (lambda (exc) + (if (uncaught-exception? exc) + (* 10 (uncaught-exception-reason exc)) + 99999)) + (lambda () + (+ 1 (thread-join! t))))) ==> 1231 + +(define thread-alive? + (let ((unique (list 'unique))) + (lambda (thread) + ; Note: this procedure raises an exception if + ; the thread terminated abnormally. + (eq? (thread-join! thread 0 unique) unique)))) + +(define (wait-for-termination! thread) + (let ((eh (current-exception-handler))) + (with-exception-handler + (lambda (exc) + (if (not (or (terminated-thread-exception? exc) + (uncaught-exception? exc))) + (eh exc))) ; unexpected exceptions are handled by eh + (lambda () + ; The following call to thread-join! will wait until the + ; thread terminates. If the thread terminated normally + ; thread-join! will return normally. If the thread + ; terminated abnormally then one of these two exception + ; objects is raised by thread-join!: + ; - terminated-thread-exception object + ; - uncaught-exception object + (thread-join! thread) + #f)))) ; ignore result of thread-join! + |
(thread-send thread msg) | procedure |
Each thread has a mailbox which stores messages delivered to the +thread in the order delivered. +
+The procedure thread-send adds the message msg at the end
+of the mailbox of thread thread and returns an unspecified
+value.
+
For example: +
+> (thread-send (current-thread) 111) +> (thread-send (current-thread) 222) +> (thread-receive) +111 +> (thread-receive) +222 + |
(thread-receive [timeout [default]]) | procedure |
(thread-mailbox-next [timeout [default]]) | procedure |
(thread-mailbox-rewind) | procedure |
(thread-mailbox-extract-and-rewind) | procedure |
To allow a thread to examine the messages in its mailbox without
+removing them from the mailbox, each thread has a mailbox cursor
+which normally points to the last message accessed in the mailbox.
+When a mailbox cursor is rewound using the procedure
+thread-mailbox-rewind or
+thread-mailbox-extract-and-rewind or thread-receive, the
+cursor does not point to a message, but the next call to
+thread-receive and thread-mailbox-next will set the
+cursor to the oldest message in the mailbox.
+
The procedure thread-receive advances the mailbox cursor of the
+current thread to the next message, removes that message from the
+mailbox, rewinds the mailbox cursor, and returns the message. When
+timeout is not specified, the current thread will wait until a
+message is available in the mailbox. When timeout is specified
+and default is not specified, a
+mailbox-receive-timeout-exception object is raised if the timeout is
+reached before a message is available. When timeout is
+specified and default is specified, default is returned if
+the timeout is reached before a message is available.
+
The procedure thread-mailbox-next behaves like
+thread-receive except that the message remains in the mailbox
+and the mailbox cursor is not rewound.
+
The procedures thread-mailbox-rewind or
+thread-mailbox-extract-and-rewind rewind the mailbox cursor of
+the current thread so that the next call to thread-mailbox-next
+and thread-receive will access the oldest message in the
+mailbox. Additionally the procedure
+thread-mailbox-extract-and-rewind will remove from the mailbox
+the message most recently accessed by a call to
+thread-mailbox-next. When thread-mailbox-next has not
+been called since the last call to thread-receive or
+thread-mailbox-rewind or
+thread-mailbox-extract-and-rewind, a call to
+thread-mailbox-extract-and-rewind only resets the mailbox
+cursor (no message is removed).
+
For example: +
+> (thread-send (current-thread) 111) +> (thread-receive 1 999) +111 +> (thread-send (current-thread) 222) +> (thread-send (current-thread) 333) +> (thread-mailbox-next 1 999) +222 +> (thread-mailbox-next 1 999) +333 +> (thread-mailbox-next 1 999) +999 +> (thread-mailbox-extract-and-rewind) +> (thread-receive 1 999) +222 +> (thread-receive 1 999) +999 + |
(mailbox-receive-timeout-exception? obj) | procedure |
(mailbox-receive-timeout-exception-procedure exc) | procedure |
(mailbox-receive-timeout-exception-arguments exc) | procedure |
Mailbox-receive-timeout-exception objects are raised by the procedures
+thread-receive and thread-mailbox-next when a timeout
+expires before a message is available and no default value is
+specified. The parameter exc must be a
+mailbox-receive-timeout-exception object.
+
The procedure mailbox-receive-timeout-exception? returns
+#t when obj is a mailbox-receive-timeout-exception
+object and #f otherwise.
+
The procedure mailbox-receive-timeout-exception-procedure
+returns the procedure that raised exc.
+
The procedure mailbox-receive-timeout-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
For example: +
+> (define (handler exc) + (if (mailbox-receive-timeout-exception? exc) + (list (mailbox-receive-timeout-exception-procedure exc) + (mailbox-receive-timeout-exception-arguments exc)) + 'not-mailbox-receive-timeout-exception)) +> (with-exception-catcher + handler + (lambda () (thread-receive 1))) +(#<procedure #2 thread-receive> (1)) + |
(mutex? obj) | procedure |
This procedure returns #t when obj is a mutex object and
+#f otherwise.
+
For example: +
+> (mutex? (make-mutex)) +#t +> (mutex? 'foo) +#f + |
(make-mutex [name]) | procedure |
This procedure returns a new mutex in the unlocked/not-abandoned +state. The optional name is an arbitrary Scheme object which +identifies the mutex (useful for debugging); it defaults to an +unspecified value. The mutex’s specific field is set to an +unspecified value. +
+For example: +
+> (make-mutex) +#<mutex #2> +> (make-mutex 'foo) +#<mutex #3 foo> + |
(mutex-name mutex) | procedure |
Returns the name of the mutex. For example: +
+> (mutex-name (make-mutex 'foo)) +foo + |
(mutex-specific mutex) | procedure |
(mutex-specific-set! mutex obj) | procedure |
The mutex-specific procedure returns the content of the
+mutex’s specific field.
+
The mutex-specific-set! procedure stores obj into the
+mutex’s specific field and returns an unspecified value.
+
For example: +
+> (define m (make-mutex)) +> (mutex-specific-set! m "hello") +> (mutex-specific m) +"hello" +> (define (mutex-lock-recursively! mutex) + (if (eq? (mutex-state mutex) (current-thread)) + (let ((n (mutex-specific mutex))) + (mutex-specific-set! mutex (+ n 1))) + (begin + (mutex-lock! mutex) + (mutex-specific-set! mutex 0)))) +> (define (mutex-unlock-recursively! mutex) + (let ((n (mutex-specific mutex))) + (if (= n 0) + (mutex-unlock! mutex) + (mutex-specific-set! mutex (- n 1))))) +> (mutex-lock-recursively! m) +> (mutex-lock-recursively! m) +> (mutex-lock-recursively! m) +> (mutex-specific m) +2 + |
(mutex-state mutex) | procedure |
Thos procedure returns information about the state of the mutex. +The possible results are: +
+not-owned:
+the mutex is in the locked/not-owned state
+
+abandoned:
+the mutex is in the unlocked/abandoned
+state
+
+not-abandoned:
+the mutex is in the unlocked/not-abandoned
+state
+
+For example: +
+(mutex-state (make-mutex)) ==> not-abandoned + +(define (thread-alive? thread) + (let ((mutex (make-mutex))) + (mutex-lock! mutex #f thread) + (let ((state (mutex-state mutex))) + (mutex-unlock! mutex) ; avoid space leak + (eq? state thread)))) + |
(mutex-lock! mutex [timeout [thread]]) | procedure |
This procedure locks mutex. If the mutex is currently
+locked, the current thread waits until the mutex is unlocked, or
+until the timeout is reached if timeout is supplied. If the
+timeout is reached, mutex-lock! returns #f. Otherwise,
+the state of the mutex is changed as follows:
+
After changing the state of the mutex, an
+abandoned-mutex-exception object is raised if the mutex was
+unlocked/abandoned before the state change, otherwise
+mutex-lock! returns #t. It is not an error if the
+mutex is owned by the current thread (but the current thread
+will have to wait).
+
For example: +
+; an implementation of a mailbox object of depth one; this +; implementation does not behave well in the presence of forced +; thread terminations using thread-terminate! (deadlock can occur +; if a thread is terminated in the middle of a put! or get! operation) + +(define (make-empty-mailbox) + (let ((put-mutex (make-mutex)) ; allow put! operation + (get-mutex (make-mutex)) + (cell #f)) + + (define (put! obj) + (mutex-lock! put-mutex #f #f) ; prevent put! operation + (set! cell obj) + (mutex-unlock! get-mutex)) ; allow get! operation + + (define (get!) + (mutex-lock! get-mutex #f #f) ; wait until object in mailbox + (let ((result cell)) + (set! cell #f) ; prevent space leaks + (mutex-unlock! put-mutex) ; allow put! operation + result)) + + (mutex-lock! get-mutex #f #f) ; prevent get! operation + + (lambda (msg) + (case msg + ((put!) put!) + ((get!) get!) + (else (error "unknown message")))))) + +(define (mailbox-put! m obj) ((m 'put!) obj)) +(define (mailbox-get! m) ((m 'get!))) + +; an alternate implementation of thread-sleep! + +(define (sleep! timeout) + (let ((m (make-mutex))) + (mutex-lock! m #f #f) + (mutex-lock! m timeout #f))) + +; a procedure that waits for one of two mutexes to unlock + +(define (lock-one-of! mutex1 mutex2) + ; this procedure assumes that neither mutex1 or mutex2 + ; are owned by the current thread + (let ((ct (current-thread)) + (done-mutex (make-mutex))) + (mutex-lock! done-mutex #f #f) + (let ((t1 (thread-start! + (make-thread + (lambda () + (mutex-lock! mutex1 #f ct) + (mutex-unlock! done-mutex))))) + (t2 (thread-start! + (make-thread + (lambda () + (mutex-lock! mutex2 #f ct) + (mutex-unlock! done-mutex)))))) + (mutex-lock! done-mutex #f #f) + (thread-terminate! t1) + (thread-terminate! t2) + (if (eq? (mutex-state mutex1) ct) + (begin + (if (eq? (mutex-state mutex2) ct) + (mutex-unlock! mutex2)) ; don't lock both + mutex1) + mutex2)))) + |
(mutex-unlock! mutex [condition-variable [timeout]]) | procedure |
This procedure unlocks the mutex by making it
+unlocked/not-abandoned. It is not an error to unlock an unlocked
+mutex and a mutex that is owned by any thread. If
+condition-variable is supplied, the current thread is blocked
+and added to the condition-variable before unlocking
+mutex; the thread can unblock at any time but no later than when
+an appropriate call to condition-variable-signal! or
+condition-variable-broadcast! is performed (see below), and no
+later than the timeout (if timeout is supplied). If there are
+threads waiting to lock this mutex, the scheduler selects a
+thread, the mutex becomes locked/owned or locked/not-owned, and the
+thread is unblocked. mutex-unlock! returns #f when the
+timeout is reached, otherwise it returns #t.
+
NOTE: The reason the thread can unblock at any time (when
+condition-variable is supplied) is that the scheduler, when it
+detects a serious problem such as a deadlock, must interrupt one of
+the blocked threads (such as the primordial thread) so that it can
+perform some appropriate action. After a thread blocked on a
+condition-variable has handled such an interrupt it would be wrong for
+the scheduler to return the thread to the blocked state, because any
+calls to condition-variable-broadcast! during the interrupt
+will have gone unnoticed. It is necessary for the thread to remain
+runnable and return from the call to mutex-unlock! with a
+result of #t.
+
NOTE: mutex-unlock! is related to the “wait” operation on
+condition variables available in other thread systems. The main
+difference is that “wait” automatically locks mutex just
+after the thread is unblocked. This operation is not performed by
+mutex-unlock! and so must be done by an explicit call to
+mutex-lock!. This has the advantages that a different timeout
+and exception-handler can be specified on the mutex-lock! and
+mutex-unlock! and the location of all the mutex operations is
+clearly apparent.
+
For example: +
+(let loop () + (mutex-lock! m) + (if (condition-is-true?) + (begin + (do-something-when-condition-is-true) + (mutex-unlock! m)) + (begin + (mutex-unlock! m cv) + (loop)))) + |
(condition-variable? obj) | procedure |
This procedure returns #t when obj is a
+condition-variable object and #f otherwise.
+
For example: +
+> (condition-variable? (make-condition-variable)) +#t +> (condition-variable? 'foo) +#f + |
(make-condition-variable [name]) | procedure |
This procedure returns a new empty condition variable. The optional +name is an arbitrary Scheme object which identifies the +condition variable (useful for debugging); it defaults to an +unspecified value. The condition variable’s specific field is set to +an unspecified value. +
+For example: +
+> (make-condition-variable) +#<condition-variable #2> + |
(condition-variable-name condition-variable) | procedure |
This procedure returns the name of the condition-variable. For +example: +
+> (condition-variable-name (make-condition-variable 'foo)) +foo + |
(condition-variable-specific condition-variable) | procedure |
(condition-variable-specific-set! condition-variable obj) | procedure |
The condition-variable-specific procedure returns the content
+of the condition-variable’s specific field.
+
The condition-variable-specific-set! procedure stores obj
+into the condition-variable’s specific field and returns
+an unspecified value.
+
For example: +
+> (define cv (make-condition-variable)) +> (condition-variable-specific-set! cv "hello") +> (condition-variable-specific cv) +"hello" + |
(condition-variable-signal! condition-variable) | procedure |
This procedure unblocks a thread blocked on the +condition-variable (if there is at least one) and returns an +unspecified value. +
+For example: +
+; an implementation of a mailbox object of depth one; this +; implementation behaves gracefully when threads are forcibly +; terminated using thread-terminate! (an abandoned-mutex-exception +; object will be raised when a put! or get! operation is attempted +; after a thread is terminated in the middle of a put! or get! +; operation) + +(define (make-empty-mailbox) + (let ((mutex (make-mutex)) + (put-condvar (make-condition-variable)) + (get-condvar (make-condition-variable)) + (full? #f) + (cell #f)) + + (define (put! obj) + (mutex-lock! mutex) + (if full? + (begin + (mutex-unlock! mutex put-condvar) + (put! obj)) + (begin + (set! cell obj) + (set! full? #t) + (condition-variable-signal! get-condvar) + (mutex-unlock! mutex)))) + + (define (get!) + (mutex-lock! mutex) + (if (not full?) + (begin + (mutex-unlock! mutex get-condvar) + (get!)) + (let ((result cell)) + (set! cell #f) ; avoid space leaks + (set! full? #f) + (condition-variable-signal! put-condvar) + (mutex-unlock! mutex) + result))) + + (lambda (msg) + (case msg + ((put!) put!) + ((get!) get!) + (else (error "unknown message")))))) + +(define (mailbox-put! m obj) ((m 'put!) obj)) +(define (mailbox-get! m) ((m 'get!))) + |
(condition-variable-broadcast! condition-variable) | procedure |
This procedure unblocks all the thread blocked on the +condition-variable and returns an unspecified value. +
+For example: +
+(define (make-semaphore n) + (vector n (make-mutex) (make-condition-variable))) + +(define (semaphore-wait! sema) + (mutex-lock! (vector-ref sema 1)) + (let ((n (vector-ref sema 0))) + (if (> n 0) + (begin + (vector-set! sema 0 (- n 1)) + (mutex-unlock! (vector-ref sema 1))) + (begin + (mutex-unlock! (vector-ref sema 1) (vector-ref sema 2)) + (semaphore-wait! sema)))) + +(define (semaphore-signal-by! sema increment) + (mutex-lock! (vector-ref sema 1)) + (let ((n (+ (vector-ref sema 0) increment))) + (vector-set! sema 0 n) + (if (> n 0) + (condition-variable-broadcast! (vector-ref sema 2))) + (mutex-unlock! (vector-ref sema 1)))) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The dynamic environment is the structure which allows the system
+to find the value returned by the standard procedures
+current-input-port and current-output-port. The
+standard procedures with-input-from-file and
+with-output-to-file extend the dynamic environment to produce a
+new dynamic environment which is in effect for the dynamic extent of
+the call to the thunk passed as their last argument. These procedures
+are essentially special purpose dynamic binding operations on hidden
+dynamic variables (one for current-input-port and one for
+current-output-port). Gambit generalizes this dynamic binding
+mechanism to allow the user to introduce new dynamic variables, called
+parameter objects, and dynamically bind them. The parameter
+objects implemented by Gambit are compatible with the specification of
+the “Parameter objects SRFI” (SRFI 39).
+
One important issue is the relationship between the dynamic +environments of the parent and child threads when a thread is created. +Each thread has its own dynamic environment that is accessed when +looking up the value bound to a parameter object by that thread. When +a thread’s dynamic environment is extended it does not affect the +dynamic environment of other threads. When a thread is created it is +given a dynamic environment whose bindings are inherited from the +parent thread. In this inherited dynamic environment the parameter +objects are bound to the same cells as the parent’s dynamic +environment (in other words an assignment of a new value to a +parameter object is visible in the other thread). +
+Another important issue is the interaction between the
+dynamic-wind procedure and dynamic environments. When a thread
+creates a continuation, the thread’s dynamic environment and the
+dynamic-wind stack are saved within the continuation (an
+alternate but equivalent point of view is that the dynamic-wind
+stack is part of the dynamic environment). When this continuation is
+invoked the required dynamic-wind before and after thunks are
+called and the saved dynamic environment is reinstated as the dynamic
+environment of the current thread. During the call to each required
+dynamic-wind before and after thunk, the dynamic environment
+and the dynamic-wind stack in effect when the corresponding
+dynamic-wind was executed are reinstated. Note that this
+specification precisely defines the semantics of calling
+call-with-current-continuation or invoking a continuation
+within a before or after thunk. The semantics are well defined even
+when a continuation created by another thread is invoked. Below is an
+example exercising the subtleties of this semantics.
+
(with-output-to-file + "foo" + (lambda () + (let ((k (call-with-current-continuation + (lambda (exit) + (with-output-to-file + "bar" + (lambda () + (dynamic-wind + (lambda () + (write '(b1)) + (force-output)) + (lambda () + (let ((x (call-with-current-continuation + (lambda (cont) (exit cont))))) + (write '(t1)) + (force-output) + x)) + (lambda () + (write '(a1)) + (force-output))))))))) + (if k + (dynamic-wind + (lambda () + (write '(b2)) + (force-output)) + (lambda () + (with-output-to-file + "baz" + (lambda () + (write '(t2)) + (force-output) + ; go back inside (with-output-to-file "bar" ...) + (k #f)))) + (lambda () + (write '(a2)) + (force-output))))))) + |
The following actions will occur when this code is executed:
+(b1)(a1) is written to “bar”, (b2) is then written to
+“foo”, (t2) is then written to “baz”, (a2) is then
+written to “foo”, and finally (b1)(t1)(a1) is written to
+“bar”.
+
(make-parameter obj [filter]) | procedure |
The dynamic environment is composed of two parts: the local +dynamic environment and the global dynamic environment. There +is a single global dynamic environment, and it is used to lookup +parameter objects that can’t be found in the local dynamic +environment. +
+The make-parameter procedure returns a new parameter
+object. The filter argument is a one argument conversion
+procedure. If it is not specified, filter defaults to the
+identity function.
+
The global dynamic environment is updated to associate the parameter +object to a new cell. The initial content of the cell is the result +of applying the conversion procedure to obj. +
+A parameter object is a procedure which accepts zero or one argument. +The cell bound to a particular parameter object in the dynamic +environment is accessed by calling the parameter object. When no +argument is passed, the content of the cell is returned. When one +argument is passed the content of the cell is updated with the result +of applying the parameter object’s conversion procedure to the +argument. Note that the conversion procedure can be used for +guaranteeing the type of the parameter object’s binding and/or to +perform some conversion of the value. +
+For example: +
+> (define radix (make-parameter 10)) +> (radix) +10 +> (radix 2) +> (radix) +2 +> (define prompt + (make-parameter + 123 + (lambda (x) + (if (string? x) + x + (object->string x))))) +> (prompt) +"123" +> (prompt "$") +> (prompt) +"$" +> (define write-shared + (make-parameter + #f + (lambda (x) + (if (boolean? x) + x + (error "only booleans are accepted by write-shared"))))) +> (write-shared 123) +*** ERROR IN ##make-parameter -- only booleans are accepted by write-shared + |
(parameterize ((procedure value)…) body) | special form |
The parameterize form, evaluates all procedure and
+value expressions in an unspecified order. All the
+procedure expressions must evaluate to procedures, either parameter
+objects or procedures accepting zero and one argument. Then,
+for each procedure p and in an unspecified order:
+
(p) “gets p’s value” and that
+the call (p x) “sets p’s value to x”.
+First, the parameterize form gets p’s value and saves it in
+a local variable. It then sets p’s value to value. It then
+processes the remaining bindings (or evaluates body if there are
+no other bindings). Then it sets p’s value to the saved value.
+These steps are performed in a dynamic-wind so that it is
+possible to use continuations to jump into and out of the body
+(i.e. the dynamic-wind’s before thunk sets p’s value to
+value and the after thunk sets p’s value to the saved value).
+
+The result(s) of the parameterize form are the result(s) of the
+body.
+
Note that using procedures instead of parameter objects may lead to
+unexpected results in multithreaded programs because the before and
+after thunks of the dynamic-wind are not called when control
+switches between threads.
+
For example: +
+> (define radix (make-parameter 2)) +> (define prompt + (make-parameter + 123 + (lambda (x) + (if (string? x) + x + (object->string x))))) +> (radix) +2 +> (parameterize ((radix 16)) (radix)) +16 +> (radix) +2 +> (define (f n) (number->string n (radix))) +> (f 10) +"1010" +> (parameterize ((radix 8)) (f 10)) +"12" +> (parameterize ((radix 8) (prompt (f 10))) (prompt)) +"1010" +> (define p + (let ((x 1)) + (lambda args + (if (null? args) x (set! x (car args)))))) +> (let* ((a (p)) + (b (parameterize ((p 2)) (list (p)))) + (c (p))) + (list a b c)) +(1 (2) 1) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
Gambit’s exception-handling model is inspired from the withdrawn
+“Exception Handling SRFI” (SRFI 12), the “Multithreading support
+SRFI” (SRFI 18), and the “Exception Handling for Programs SRFI”
+(SRFI 34). The two fundamental operations are the dynamic binding of
+an exception handler (i.e. the procedure
+with-exception-handler) and the invocation of the exception
+handler (i.e. the procedure raise).
+
All predefined procedures which check for errors (including type +errors, memory allocation errors, host operating-system errors, etc) +report these errors using the exception-handling system (i.e. they +“raise” an exception that can be handled in a user-defined exception +handler). When an exception is raised and the exception is not +handled by a user-defined exception handler, the predefined exception +handler will display an error message (if the primordial thread raised +the exception) or the thread will silently terminate with no error +message (if it is not the primordial thread that raised the +exception). This default behavior can be changed through the +-:d runtime option (see section Runtime options). +
+Predefined procedures normally raise exceptions by performing a
+tail-call to the exception handler (the exceptions are “complex”
+procedures such as eval, compile-file, read,
+write, etc). This means that the continuation of the exception
+handler and of the REPL that may be started due to this is normally
+the continuation of the predefined procedure that raised the
+exception. By exiting the REPL with the ,(c expression)
+command it is thus possible to resume the program as though the call
+to the predefined procedure returned the value of expression.
+For example:
+
> (define (f x) (+ (car x) 1))
+> (f 2) ; typo... we meant to say (f '(2))
+*** ERROR IN f, (console)@1.18 -- (Argument 1) PAIR expected
+(car 2)
+1> ,(c 2)
+3
+ |
(current-exception-handler [new-exception-handler]) | procedure |
The parameter object current-exception-handler is bound to the
+current exception-handler. Calling this procedure with no argument
+returns the current exception-handler and calling this procedure with
+one argument sets the current exception-handler to
+new-exception-handler.
+
For example: +
+> (current-exception-handler) +#<procedure #2 primordial-exception-handler> +> (current-exception-handler (lambda (exc) (pp exc) 999)) +> (/ 1 0) +#<divide-by-zero-exception #3> +999 + |
(with-exception-handler handler thunk) | procedure |
Returns the result(s) of calling thunk with no arguments. The +handler, which must be a procedure, is installed as the current +exception-handler in the dynamic environment in effect during the call +to thunk. Note that the dynamic environment in effect during +the call to handler has handler as the exception-handler. +Consequently, an exception raised during the call to handler may +lead to an infinite loop. +
+For example: +
+> (with-exception-handler + (lambda (e) (write e) 5) + (lambda () (+ 1 (* 2 3) 4))) +11 +> (with-exception-handler + (lambda (e) (write e) 5) + (lambda () (+ 1 (* 'foo 3) 4))) +#<type-exception #2>10 +> (with-exception-handler + (lambda (e) (write e 9)) + (lambda () (+ 1 (* 'foo 3) 4))) +infinite loop + |
(with-exception-catcher handler thunk) | procedure |
Returns the result(s) of calling thunk with no arguments. A new
+exception-handler is installed as the current exception-handler in the
+dynamic environment in effect during the call to thunk. This
+new exception-handler will call the handler, which must be a
+procedure, with the exception object as an argument and with the same
+continuation as the call to with-exception-catcher. This
+implies that the dynamic environment in effect during the call to
+handler is the same as the one in effect at the call to
+with-exception-catcher. Consequently, an exception raised
+during the call to handler will not lead to an infinite loop.
+
For example: +
+> (with-exception-catcher + (lambda (e) (write e) 5) + (lambda () (+ 1 (* 2 3) 4))) +11 +> (with-exception-catcher + (lambda (e) (write e) 5) + (lambda () (+ 1 (* 'foo 3) 4))) +#<type-exception #2>5 +> (with-exception-catcher + (lambda (e) (write e 9)) + (lambda () (+ 1 (* 'foo 3) 4))) +*** ERROR IN (console)@7.1 -- (Argument 2) OUTPUT PORT expected +(write '#<type-exception #3> 9) + |
(raise obj) | procedure |
This procedure tail-calls the current exception-handler with obj
+as the sole argument. If the exception-handler returns, the
+continuation of the call to raise is invoked.
+
For example: +
+> (with-exception-handler + (lambda (exc) + (pp exc) + 100) + (lambda () + (+ 1 (raise "hello")))) +"hello" +101 + |
(abort obj) | procedure |
(noncontinuable-exception? obj) | procedure |
(noncontinuable-exception-reason exc) | procedure |
The procedure abort calls the current exception-handler with
+obj as the sole argument. If the exception-handler returns, the
+procedure abort will be tail-called with a
+noncontinuable-exception object, whose reason field is obj, as
+sole argument.
+
Noncontinuable-exception objects are raised by the abort
+procedure when the exception-handler returns. The parameter exc
+must be a noncontinuable-exception object.
+
The procedure noncontinuable-exception? returns
+#t when obj is a noncontinuable-exception
+object and #f otherwise.
+
The procedure noncontinuable-exception-reason returns the
+argument of the call to abort that raised exc.
+
For example: +
+> (call-with-current-continuation
+ (lambda (k)
+ (with-exception-handler
+ (lambda (exc)
+ (pp exc)
+ (if (noncontinuable-exception? exc)
+ (k (list (noncontinuable-exception-reason exc)))
+ 100))
+ (lambda ()
+ (+ 1 (abort "hello"))))))
+"hello"
+#<noncontinuable-exception #2>
+("hello")
+ |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(heap-overflow-exception? obj) | procedure |
Heap-overflow-exception objects are raised when the allocation of an +object would cause the heap to use more memory space than is available. +
+The procedure heap-overflow-exception? returns
+#t when obj is a heap-overflow-exception
+object and #f otherwise.
+
For example: +
+> (define (handler exc) + (if (heap-overflow-exception? exc) + exc + 'not-heap-overflow-exception)) +> (with-exception-catcher + handler + (lambda () + (define (f x) (f (cons 1 x))) + (f '()))) +#<heap-overflow-exception #2> + |
(stack-overflow-exception? obj) | procedure |
Stack-overflow-exception objects are raised when the allocation of a +continuation frame would cause the heap to use more memory space than +is available. +
+The procedure stack-overflow-exception? returns
+#t when obj is a stack-overflow-exception
+object and #f otherwise.
+
For example: +
+> (define (handler exc) + (if (stack-overflow-exception? exc) + exc + 'not-stack-overflow-exception)) +> (with-exception-catcher + handler + (lambda () + (define (f) (+ 1 (f))) + (f))) +#<stack-overflow-exception #2> + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(os-exception? obj) | procedure |
(os-exception-procedure exc) | procedure |
(os-exception-arguments exc) | procedure |
(os-exception-code exc) | procedure |
(os-exception-message exc) | procedure |
Os-exception objects are raised by procedures which access the host +operating-system’s services when the requested operation fails. The +parameter exc must be a os-exception object. +
+The procedure os-exception? returns
+#t when obj is a os-exception
+object and #f otherwise.
+
The procedure os-exception-procedure
+returns the procedure that raised exc.
+
The procedure os-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
The procedure os-exception-code returns an exact integer error
+code that can be converted to a string by the err-code->string
+procedure. Note that the error code is operating-system dependent.
+
The procedure os-exception-message returns
+#f or a string giving details of the exception in a
+human-readable form.
+
For example: +
+> (define (handler exc)
+ (if (os-exception? exc)
+ (list (os-exception-procedure exc)
+ (os-exception-arguments exc)
+ (err-code->string (os-exception-code exc))
+ (os-exception-message exc))
+ 'not-os-exception))
+> (with-exception-catcher
+ handler
+ (lambda () (host-info "x.y.z")))
+(#<procedure #2 host-info> ("x.y.z") "Unknown host" #f)
+ |
(no-such-file-or-directory-exception? obj) | procedure |
(no-such-file-or-directory-exception-procedure exc) | procedure |
(no-such-file-or-directory-exception-arguments exc) | procedure |
No-such-file-or-directory-exception objects are raised by procedures
+which access the filesystem (such as open-input-file and
+directory-files) when the path specified can’t be found on the
+filesystem. The parameter exc must be a
+no-such-file-or-directory-exception object.
+
The procedure no-such-file-or-directory-exception? returns
+#t when obj is a no-such-file-or-directory-exception
+object and #f otherwise.
+
The procedure no-such-file-or-directory-exception-procedure
+returns the procedure that raised exc.
+
The procedure no-such-file-or-directory-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
For example: +
+> (define (handler exc)
+ (if (no-such-file-or-directory-exception? exc)
+ (list (no-such-file-or-directory-exception-procedure exc)
+ (no-such-file-or-directory-exception-arguments exc))
+ 'not-no-such-file-or-directory-exception))
+> (with-exception-catcher
+ handler
+ (lambda () (with-input-from-file "nofile" read)))
+(#<procedure #2 with-input-from-file> ("nofile" #<procedure #3 read>))
+ |
(unbound-os-environment-variable-exception? obj) | procedure |
(unbound-os-environment-variable-exception-procedure exc) | procedure |
(unbound-os-environment-variable-exception-arguments exc) | procedure |
Unbound-os-environment-variable-exception objects are raised when an
+unbound operating-system environment variable is accessed by the
+procedures getenv and setenv. The parameter exc
+must be an unbound-os-environment-variable-exception object.
+
The procedure unbound-os-environment-variable-exception? returns
+#t when obj is an unbound-os-environment-variable-exception
+object and #f otherwise.
+
The procedure unbound-os-environment-variable-exception-procedure
+returns the procedure that raised exc.
+
The procedure unbound-os-environment-variable-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
For example: +
+> (define (handler exc)
+ (if (unbound-os-environment-variable-exception? exc)
+ (list (unbound-os-environment-variable-exception-procedure exc)
+ (unbound-os-environment-variable-exception-arguments exc))
+ 'not-unbound-os-environment-variable-exception))
+> (with-exception-catcher
+ handler
+ (lambda () (getenv "DOES_NOT_EXIST")))
+(#<procedure #2 getenv> ("DOES_NOT_EXIST"))
+ |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(scheduler-exception? obj) | procedure |
(scheduler-exception-reason exc) | procedure |
Scheduler-exception objects are raised by the scheduler when some +operation requested from the host operating system failed +(e.g. checking the status of the devices in order to wake up threads +waiting to perform I/O on these devices). The parameter exc +must be a scheduler-exception object. +
+The procedure scheduler-exception? returns
+#t when obj is a scheduler-exception
+object and #f otherwise.
+
The procedure scheduler-exception-reason returns the
+os-exception object that describes the failure detected by the
+scheduler.
+
(deadlock-exception? obj) | procedure |
Deadlock-exception objects are raised when the scheduler discovers +that all threads are blocked and can make no further progress. In +that case the scheduler unblocks the primordial-thread and forces it +to raise a deadlock-exception object. +
+The procedure deadlock-exception? returns #t when
+obj is a deadlock-exception object and #f otherwise.
+
For example: +
+> (define (handler exc) + (if (deadlock-exception? exc) + exc + 'not-deadlock-exception)) +> (with-exception-catcher + handler + (lambda () (read (open-vector)))) +#<deadlock-exception #2> + |
(abandoned-mutex-exception? obj) | procedure |
Abandoned-mutex-exception objects are raised when the current thread
+locks a mutex that was owned by a thread which terminated (see
+mutex-lock!).
+
The procedure abandoned-mutex-exception? returns
+#t when obj is a abandoned-mutex-exception
+object and #f otherwise.
+
For example: +
+> (define (handler exc) + (if (abandoned-mutex-exception? exc) + exc + 'not-abandoned-mutex-exception)) +> (with-exception-catcher + handler + (lambda () + (let ((m (make-mutex))) + (thread-join! + (thread-start! + (make-thread + (lambda () (mutex-lock! m))))) + (mutex-lock! m)))) +#<abandoned-mutex-exception #2> + |
(join-timeout-exception? obj) | procedure |
(join-timeout-exception-procedure exc) | procedure |
(join-timeout-exception-arguments exc) | procedure |
Join-timeout-exception objects are raised when a call to the
+thread-join! procedure reaches its timeout before the target
+thread terminates and a timeout-value parameter is not specified. The
+parameter exc must be a join-timeout-exception object.
+
The procedure join-timeout-exception? returns
+#t when obj is a join-timeout-exception
+object and #f otherwise.
+
The procedure join-timeout-exception-procedure
+returns the procedure that raised exc.
+
The procedure join-timeout-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
For example: +
+> (define (handler exc) + (if (join-timeout-exception? exc) + (list (join-timeout-exception-procedure exc) + (join-timeout-exception-arguments exc)) + 'not-join-timeout-exception)) +> (with-exception-catcher + handler + (lambda () + (thread-join! + (thread-start! + (make-thread + (lambda () (thread-sleep! 10)))) + 5))) +(#<procedure #2 thread-join!> (#<thread #3> 5)) + |
(started-thread-exception? obj) | procedure |
(started-thread-exception-procedure exc) | procedure |
(started-thread-exception-arguments exc) | procedure |
Started-thread-exception objects are raised when the target thread of
+a call to the procedure thread-start! is already started. The
+parameter exc must be a started-thread-exception object.
+
The procedure started-thread-exception? returns
+#t when obj is a started-thread-exception
+object and #f otherwise.
+
The procedure started-thread-exception-procedure
+returns the procedure that raised exc.
+
The procedure started-thread-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
For example: +
+> (define (handler exc) + (if (started-thread-exception? exc) + (list (started-thread-exception-procedure exc) + (started-thread-exception-arguments exc)) + 'not-started-thread-exception)) +> (with-exception-catcher + handler + (lambda () + (let ((t (make-thread (lambda () (expt 2 1000))))) + (thread-start! t) + (thread-start! t)))) +(#<procedure #2 thread-start!> (#<thread #3>)) + |
(terminated-thread-exception? obj) | procedure |
(terminated-thread-exception-procedure exc) | procedure |
(terminated-thread-exception-arguments exc) | procedure |
Terminated-thread-exception objects are raised when the
+thread-join! procedure is called and the target thread has
+terminated as a result of a call to the thread-terminate!
+procedure. The parameter exc must be a
+terminated-thread-exception object.
+
The procedure terminated-thread-exception? returns
+#t when obj is a terminated-thread-exception
+object and #f otherwise.
+
The procedure terminated-thread-exception-procedure
+returns the procedure that raised exc.
+
The procedure terminated-thread-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
For example: +
+> (define (handler exc) + (if (terminated-thread-exception? exc) + (list (terminated-thread-exception-procedure exc) + (terminated-thread-exception-arguments exc)) + 'not-terminated-thread-exception)) +> (with-exception-catcher + handler + (lambda () + (thread-join! + (thread-start! + (make-thread + (lambda () (thread-terminate! (current-thread)))))))) +(#<procedure #2 thread-join!> (#<thread #3>)) + |
(uncaught-exception? obj) | procedure |
(uncaught-exception-procedure exc) | procedure |
(uncaught-exception-arguments exc) | procedure |
(uncaught-exception-reason exc) | procedure |
Uncaught-exception objects are raised when an object is raised in a +thread and that thread does not handle it (i.e. the thread terminated +because it did not catch an exception it raised). The parameter +exc must be an uncaught-exception object. +
+The procedure uncaught-exception? returns
+#t when obj is an uncaught-exception
+object and #f otherwise.
+
The procedure uncaught-exception-procedure
+returns the procedure that raised exc.
+
The procedure uncaught-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
The procedure uncaught-exception-reason returns the object that
+was raised by the thread and not handled by that thread.
+
For example: +
+> (define (handler exc) + (if (uncaught-exception? exc) + (list (uncaught-exception-procedure exc) + (uncaught-exception-arguments exc) + (uncaught-exception-reason exc)) + 'not-uncaught-exception)) +> (with-exception-catcher + handler + (lambda () + (thread-join! + (thread-start! + (make-thread + (lambda () (open-input-file "data" 99))))))) +(#<procedure #2 thread-join!> + (#<thread #3>) + #<wrong-number-of-arguments-exception #4>) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(cfun-conversion-exception? obj) | procedure |
(cfun-conversion-exception-procedure exc) | procedure |
(cfun-conversion-exception-arguments exc) | procedure |
(cfun-conversion-exception-code exc) | procedure |
(cfun-conversion-exception-message exc) | procedure |
Cfun-conversion-exception objects are raised by the C-interface when +converting between the Scheme representation and the C representation +of a value during a call from Scheme to C. The parameter exc +must be a cfun-conversion-exception object. +
+The procedure cfun-conversion-exception? returns #t when
+obj is a cfun-conversion-exception object and #f
+otherwise.
+
The procedure cfun-conversion-exception-procedure returns the
+procedure that raised exc.
+
The procedure cfun-conversion-exception-arguments returns the
+list of arguments of the procedure that raised exc.
+
The procedure cfun-conversion-exception-code returns an exact
+integer error code that can be converted to a string by the
+err-code->string procedure.
+
The procedure cfun-conversion-exception-message returns
+#f or a string giving details of the exception in a
+human-readable form.
+
For example: +
+$ cat test1.scm +(define weird + (c-lambda (char-string) nonnull-char-string + "___result = ___arg1;")) +$ gsc test1.scm +$ gsi +Gambit v4.6.1 + +> (load "test1") +"/Users/feeley/gambit/doc/test1.o1" +> (weird "hello") +"hello" +> (define (handler exc) + (if (cfun-conversion-exception? exc) + (list (cfun-conversion-exception-procedure exc) + (cfun-conversion-exception-arguments exc) + (err-code->string (cfun-conversion-exception-code exc)) + (cfun-conversion-exception-message exc)) + 'not-cfun-conversion-exception)) +> (with-exception-catcher + handler + (lambda () (weird 'not-a-string))) +(#<procedure #2 weird> + (not-a-string) + "(Argument 1) Can't convert to C char-string" + #f) +> (with-exception-catcher + handler + (lambda () (weird #f))) +(#<procedure #2 weird> + (#f) + "Can't convert result from C nonnull-char-string" + #f) + |
(sfun-conversion-exception? obj) | procedure |
(sfun-conversion-exception-procedure exc) | procedure |
(sfun-conversion-exception-arguments exc) | procedure |
(sfun-conversion-exception-code exc) | procedure |
(sfun-conversion-exception-message exc) | procedure |
Sfun-conversion-exception objects are raised by the C-interface when +converting between the Scheme representation and the C representation +of a value during a call from C to Scheme. The parameter exc +must be a sfun-conversion-exception object. +
+The procedure sfun-conversion-exception? returns #t when
+obj is a sfun-conversion-exception object and #f
+otherwise.
+
The procedure sfun-conversion-exception-procedure returns the
+procedure that raised exc.
+
The procedure sfun-conversion-exception-arguments returns the
+list of arguments of the procedure that raised exc.
+
The procedure sfun-conversion-exception-code returns an exact
+integer error code that can be converted to a string by the
+err-code->string procedure.
+
The procedure sfun-conversion-exception-message returns
+#f or a string giving details of the exception in a
+human-readable form.
+
For example: +
+$ cat test2.scm +(c-define (f str) (nonnull-char-string) int "f" "" + (string->number str)) +(define t1 (c-lambda () int "___result = f (\"123\");")) +(define t2 (c-lambda () int "___result = f (0);")) +(define t3 (c-lambda () int "___result = f (\"1.5\");")) +$ gsc test2.scm +$ gsi +Gambit v4.6.1 + +> (load "test2") +"/u/feeley/test2.o1" +> (t1) +123 +> (define (handler exc) + (if (sfun-conversion-exception? exc) + (list (sfun-conversion-exception-procedure exc) + (sfun-conversion-exception-arguments exc) + (err-code->string (sfun-conversion-exception-code exc)) + (sfun-conversion-exception-message exc)) + 'not-sfun-conversion-exception)) +> (with-exception-catcher handler t2) +(#<procedure #2 f> + () + "(Argument 1) Can't convert from C nonnull-char-string" + #f) +> (with-exception-catcher handler t3) +(#<procedure #2 f> () "Can't convert result to C int" #f) + |
(multiple-c-return-exception? obj) | procedure |
Multiple-c-return-exception objects are raised by the C-interface when
+a C to Scheme procedure call returns and that call’s stack frame is no
+longer on the C stack because the call has already returned, or has
+been removed from the C stack by a longjump.
+
The procedure multiple-c-return-exception? returns #t
+when obj is a multiple-c-return-exception object and #f
+otherwise.
+
For example: +
+$ cat test3.scm +(c-define (f str) (char-string) scheme-object "f" "" + (pp (list 'entry 'str= str)) + (let ((k (call-with-current-continuation (lambda (k) k)))) + (pp (list 'exit 'k= k)) + k)) +(define scheme-to-c-to-scheme-and-back + (c-lambda (char-string) scheme-object + "___result = f (___arg1);")) +$ gsc test3.scm +$ gsi +Gambit v4.6.1 + +> (load "test3") +"/Users/feeley/gambit/doc/test3.o1" +> (define (handler exc) + (if (multiple-c-return-exception? exc) + exc + 'not-multiple-c-return-exception)) +> (with-exception-catcher + handler + (lambda () + (let ((c (scheme-to-c-to-scheme-and-back "hello"))) + (pp c) + (c 999)))) +(entry str= "hello") +(exit k= #<procedure #2>) +#<procedure #2> +(exit k= 999) +#<multiple-c-return-exception #3> + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(datum-parsing-exception? obj) | procedure |
(datum-parsing-exception-kind exc) | procedure |
(datum-parsing-exception-parameters exc) | procedure |
(datum-parsing-exception-readenv exc) | procedure |
Datum-parsing-exception objects are raised by the reader (i.e. the
+read procedure) when the input does not conform to the grammar
+for datum. The parameter exc must be a datum-parsing-exception
+object.
+
The procedure datum-parsing-exception? returns #t when
+obj is a datum-parsing-exception object and #f
+otherwise.
+
The procedure datum-parsing-exception-kind returns a symbol
+denoting the kind of parsing error that was encountered by the
+reader when it raised exc. Here is a table of the possible
+return values:
+
datum-or-eof-expected | Datum or EOF expected |
datum-expected | Datum expected |
improperly-placed-dot | Improperly placed dot |
incomplete-form-eof-reached | Incomplete form, EOF reached |
incomplete-form | Incomplete form |
character-out-of-range | Character out of range |
invalid-character-name | Invalid ’#\’ name |
illegal-character | Illegal character |
s8-expected | Signed 8 bit exact integer expected |
u8-expected | Unsigned 8 bit exact integer expected |
s16-expected | Signed 16 bit exact integer expected |
u16-expected | Unsigned 16 bit exact integer expected |
s32-expected | Signed 32 bit exact integer expected |
u32-expected | Unsigned 32 bit exact integer expected |
s64-expected | Signed 64 bit exact integer expected |
u64-expected | Unsigned 64 bit exact integer expected |
inexact-real-expected | Inexact real expected |
invalid-hex-escape | Invalid hexadecimal escape |
invalid-escaped-character | Invalid escaped character |
open-paren-expected | ’(’ expected |
invalid-token | Invalid token |
invalid-sharp-bang-name | Invalid ’#!’ name |
duplicate-label-definition | Duplicate definition for label |
missing-label-definition | Missing definition for label |
illegal-label-definition | Illegal definition of label |
invalid-infix-syntax-character | Invalid infix syntax character |
invalid-infix-syntax-number | Invalid infix syntax number |
invalid-infix-syntax | Invalid infix syntax |
The procedure datum-parsing-exception-parameters returns a list
+of the parameters associated with the parsing error that was
+encountered by the reader when it raised exc.
+
For example: +
+> (define (handler exc)
+ (if (datum-parsing-exception? exc)
+ (list (datum-parsing-exception-kind exc)
+ (datum-parsing-exception-parameters exc))
+ 'not-datum-parsing-exception))
+> (with-exception-catcher
+ handler
+ (lambda ()
+ (with-input-from-string "(s #\\pace)" read)))
+(invalid-character-name ("pace"))
+ |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(expression-parsing-exception? obj) | procedure |
(expression-parsing-exception-kind exc) | procedure |
(expression-parsing-exception-parameters exc) | procedure |
(expression-parsing-exception-source exc) | procedure |
Expression-parsing-exception objects are raised by the evaluator and
+compiler (i.e. the procedures eval, compile-file, etc)
+when the input does not conform to the grammar for expression. The
+parameter exc must be a expression-parsing-exception object.
+
The procedure expression-parsing-exception? returns #t when
+obj is a expression-parsing-exception object and #f
+otherwise.
+
The procedure expression-parsing-exception-kind returns a
+symbol denoting the kind of parsing error that was encountered by the
+evaluator or compiler when it raised exc. Here is a table of
+the possible return values:
+
id-expected | Identifier expected |
ill-formed-namespace | Ill-formed namespace |
ill-formed-namespace-prefix | Ill-formed namespace prefix |
namespace-prefix-must-be-string | Namespace prefix must be a string |
macro-used-as-variable | Macro name can’t be used as a variable |
variable-is-immutable | Variable is immutable |
ill-formed-macro-transformer | Macro transformer must be a lambda expression |
reserved-used-as-variable | Reserved identifier can’t be used as a variable |
ill-formed-special-form | Ill-formed special form |
cannot-open-file | Can’t open file |
filename-expected | Filename expected |
ill-placed-define | Ill-placed ’define’ |
ill-placed-**include | Ill-placed ’##include’ |
ill-placed-**define-macro | Ill-placed ’##define-macro’ |
ill-placed-**declare | Ill-placed ’##declare’ |
ill-placed-**namespace | Ill-placed ’##namespace’ |
ill-formed-expression | Ill-formed expression |
unsupported-special-form | Interpreter does not support |
ill-placed-unquote | Ill-placed ’unquote’ |
ill-placed-unquote-splicing | Ill-placed ’unquote-splicing’ |
parameter-must-be-id | Parameter must be an identifier |
parameter-must-be-id-or-default | Parameter must be an identifier or default binding |
duplicate-parameter | Duplicate parameter in parameter list |
ill-placed-dotted-rest-parameter | Ill-placed dotted rest parameter |
parameter-expected-after-rest | #!rest must be followed by a parameter |
ill-formed-default | Ill-formed default binding |
ill-placed-optional | Ill-placed #!optional |
ill-placed-rest | Ill-placed #!rest |
ill-placed-key | Ill-placed #!key |
key-expected-after-rest | #!key expected after rest parameter |
ill-placed-default | Ill-placed default binding |
duplicate-variable-definition | Duplicate definition of a variable |
empty-body | Body must contain at least one expression |
variable-must-be-id | Defined variable must be an identifier |
else-clause-not-last | Else clause must be last |
ill-formed-selector-list | Ill-formed selector list |
duplicate-variable-binding | Duplicate variable in bindings |
ill-formed-binding-list | Ill-formed binding list |
ill-formed-call | Ill-formed procedure call |
ill-formed-cond-expand | Ill-formed ’cond-expand’ |
unfulfilled-cond-expand | Unfulfilled ’cond-expand’ |
The procedure expression-parsing-exception-parameters returns a list
+of the parameters associated with the parsing error that was
+encountered by the evaluator or compiler when it raised exc.
+
For example: +
+> (define (handler exc) + (if (expression-parsing-exception? exc) + (list (expression-parsing-exception-kind exc) + (expression-parsing-exception-parameters exc)) + 'not-expression-parsing-exception)) +> (with-exception-catcher + handler + (lambda () + (eval '(+ do 1)))) +(reserved-used-as-variable (do)) + |
(unbound-global-exception? obj) | procedure |
(unbound-global-exception-variable exc) | procedure |
(unbound-global-exception-code exc) | procedure |
(unbound-global-exception-rte exc) | procedure |
Unbound-global-exception objects are raised when an unbound global +variable is accessed. The parameter exc must be an +unbound-global-exception object. +
+The procedure unbound-global-exception? returns
+#t when obj is an unbound-global-exception
+object and #f otherwise.
+
The procedure unbound-global-exception-variable returns a
+symbol identifying the unbound global variable.
+
For example: +
+> (define (handler exc) + (if (unbound-global-exception? exc) + (list 'variable= (unbound-global-exception-variable exc)) + 'not-unbound-global-exception)) +> (with-exception-catcher + handler + (lambda () foo)) +(variable= foo) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(type-exception? obj) | procedure |
(type-exception-procedure exc) | procedure |
(type-exception-arguments exc) | procedure |
(type-exception-arg-num exc) | procedure |
(type-exception-type-id exc) | procedure |
Type-exception objects are raised when a primitive procedure is called +with an argument of incorrect type (i.e. when a run time type-check +fails). The parameter exc must be a type-exception object. +
+The procedure type-exception? returns
+#t when obj is a type-exception
+object and #f otherwise.
+
The procedure type-exception-procedure
+returns the procedure that raised exc.
+
The procedure type-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
The procedure type-exception-arg-num returns the position of the
+argument whose type is incorrect. Position 1 is the first argument.
+
The procedure type-exception-type-id returns an identifier of
+the type expected. The type-id can be a symbol, such as number
+and string-or-nonnegative-fixnum, or a record type descriptor.
+
For example: +
+> (define (handler exc) + (if (type-exception? exc) + (list (type-exception-procedure exc) + (type-exception-arguments exc) + (type-exception-arg-num exc) + (type-exception-type-id exc)) + 'not-type-exception)) +> (with-exception-catcher + handler + (lambda () (vector-ref '#(a b c) 'foo))) +(#<procedure #2 vector-ref> (#(a b c) foo) 2 exact-integer) +> (with-exception-catcher + handler + (lambda () (time->seconds 'foo))) +(#<procedure #3 time->seconds> (foo) 1 #<type #4 time>) + |
(range-exception? obj) | procedure |
(range-exception-procedure exc) | procedure |
(range-exception-arguments exc) | procedure |
(range-exception-arg-num exc) | procedure |
Range-exception objects are raised when a numeric parameter is not in +the allowed range. The parameter exc must be a range-exception +object. +
+The procedure range-exception? returns #t when obj
+is a range-exception object and #f otherwise.
+
The procedure range-exception-procedure
+returns the procedure that raised exc.
+
The procedure range-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
The procedure range-exception-arg-num returns the position of
+the argument which is not in the allowed range. Position 1 is the
+first argument.
+
For example: +
+> (define (handler exc)
+ (if (range-exception? exc)
+ (list (range-exception-procedure exc)
+ (range-exception-arguments exc)
+ (range-exception-arg-num exc))
+ 'not-range-exception))
+> (with-exception-catcher
+ handler
+ (lambda () (string-ref "abcde" 10)))
+(#<procedure #2 string-ref> ("abcde" 10) 2)
+ |
(divide-by-zero-exception? obj) | procedure |
(divide-by-zero-exception-procedure exc) | procedure |
(divide-by-zero-exception-arguments exc) | procedure |
Divide-by-zero-exception objects are raised when a division by zero is +attempted. The parameter exc must be a divide-by-zero-exception +object. +
+The procedure divide-by-zero-exception? returns
+#t when obj is a divide-by-zero-exception
+object and #f otherwise.
+
The procedure divide-by-zero-exception-procedure
+returns the procedure that raised exc.
+
The procedure divide-by-zero-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
For example: +
+> (define (handler exc) + (if (divide-by-zero-exception? exc) + (list (divide-by-zero-exception-procedure exc) + (divide-by-zero-exception-arguments exc)) + 'not-divide-by-zero-exception)) +> (with-exception-catcher + handler + (lambda () (/ 5 0 7))) +(#<procedure #2 /> (5 0 7)) + |
(improper-length-list-exception? obj) | procedure |
(improper-length-list-exception-procedure exc) | procedure |
(improper-length-list-exception-arguments exc) | procedure |
(improper-length-list-exception-arg-num exc) | procedure |
Improper-length-list-exception objects are raised by the map
+and for-each procedures when they are called with two or more
+list arguments and the lists are not of the same length. The
+parameter exc must be an improper-length-list-exception object.
+
The procedure improper-length-list-exception? returns
+#t when obj is an improper-length-list-exception
+object and #f otherwise.
+
The procedure improper-length-list-exception-procedure
+returns the procedure that raised exc.
+
The procedure improper-length-list-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
The procedure improper-length-list-exception-arg-num returns
+the position of the argument whose length is the shortest. Position 1
+is the first argument.
+
For example: +
+> (define (handler exc) + (if (improper-length-list-exception? exc) + (list (improper-length-list-exception-procedure exc) + (improper-length-list-exception-arguments exc) + (improper-length-list-exception-arg-num exc)) + 'not-improper-length-list-exception)) +> (with-exception-catcher + handler + (lambda () (map + '(1 2) '(3) '(4 5)))) +(#<procedure #2 map> (#<procedure #3 +> (1 2) (3) (4 5)) 3) + |
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+ |
+ |
+ |
+ |
+ |
+
(wrong-number-of-arguments-exception? obj) | procedure |
(wrong-number-of-arguments-exception-procedure exc) | procedure |
(wrong-number-of-arguments-exception-arguments exc) | procedure |
Wrong-number-of-arguments-exception objects are raised when a +procedure is called with the wrong number of arguments. The parameter +exc must be a wrong-number-of-arguments-exception object. +
+The procedure wrong-number-of-arguments-exception? returns
+#t when obj is a wrong-number-of-arguments-exception
+object and #f otherwise.
+
The procedure wrong-number-of-arguments-exception-procedure
+returns the procedure that raised exc.
+
The procedure wrong-number-of-arguments-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
For example: +
+> (define (handler exc)
+ (if (wrong-number-of-arguments-exception? exc)
+ (list (wrong-number-of-arguments-exception-procedure exc)
+ (wrong-number-of-arguments-exception-arguments exc))
+ 'not-wrong-number-of-arguments-exception))
+> (with-exception-catcher
+ handler
+ (lambda () (open-input-file "data" 99)))
+(#<procedure #2 open-input-file> ("data" 99))
+ |
(number-of-arguments-limit-exception? obj) | procedure |
(number-of-arguments-limit-exception-procedure exc) | procedure |
(number-of-arguments-limit-exception-arguments exc) | procedure |
Number-of-arguments-limit-exception objects are raised by the
+apply procedure when the procedure being called is passed more
+than 8192 arguments. The parameter exc must be a
+number-of-arguments-limit-exception object.
+
The procedure number-of-arguments-limit-exception? returns
+#t when obj is a number-of-arguments-limit-exception
+object and #f otherwise.
+
The procedure number-of-arguments-limit-exception-procedure
+returns the target procedure of the call to apply that raised
+exc.
+
The procedure number-of-arguments-limit-exception-arguments
+returns the list of arguments of the target procedure of the call to
+apply that raised exc.
+
For example: +
+> (define (iota n) (if (= n 0) '() (cons n (iota (- n 1))))) +> (define (handler exc) + (if (number-of-arguments-limit-exception? exc) + (list (number-of-arguments-limit-exception-procedure exc) + (length (number-of-arguments-limit-exception-arguments exc))) + 'not-number-of-arguments-limit-exception)) +> (with-exception-catcher + handler + (lambda () (apply + 1 2 3 (iota 8190)))) +(#<procedure #2 +> 8193) + |
(nonprocedure-operator-exception? obj) | procedure |
(nonprocedure-operator-exception-operator exc) | procedure |
(nonprocedure-operator-exception-arguments exc) | procedure |
(nonprocedure-operator-exception-code exc) | procedure |
(nonprocedure-operator-exception-rte exc) | procedure |
Nonprocedure-operator-exception objects are raised when a procedure +call is executed and the operator position is not a procedure. The +parameter exc must be an nonprocedure-operator-exception object. +
+The procedure nonprocedure-operator-exception? returns
+#t when obj is an nonprocedure-operator-exception
+object and #f otherwise.
+
The procedure nonprocedure-operator-exception-operator returns
+the value in operator position of the procedure call that raised
+exc.
+
The procedure nonprocedure-operator-exception-arguments returns
+the list of arguments of the procedure call that raised exc.
+
For example: +
+> (define (handler exc) + (if (nonprocedure-operator-exception? exc) + (list (nonprocedure-operator-exception-operator exc) + (nonprocedure-operator-exception-arguments exc)) + 'not-nonprocedure-operator-exception)) +> (with-exception-catcher + handler + (lambda () (11 22 33))) +(11 (22 33)) + |
(unknown-keyword-argument-exception? obj) | procedure |
(unknown-keyword-argument-exception-procedure exc) | procedure |
(unknown-keyword-argument-exception-arguments exc) | procedure |
Unknown-keyword-argument-exception objects are raised when a procedure +accepting keyword arguments is called and one of the keywords supplied +is not among those that are expected. The parameter exc must be +an unknown-keyword-argument-exception object. +
+The procedure unknown-keyword-argument-exception? returns
+#t when obj is an unknown-keyword-argument-exception
+object and #f otherwise.
+
The procedure unknown-keyword-argument-exception-procedure
+returns the procedure that raised exc.
+
The procedure unknown-keyword-argument-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
For example: +
+> (define (handler exc) + (if (unknown-keyword-argument-exception? exc) + (list (unknown-keyword-argument-exception-procedure exc) + (unknown-keyword-argument-exception-arguments exc)) + 'not-unknown-keyword-argument-exception)) +> (with-exception-catcher + handler + (lambda () ((lambda (#!key (foo 5)) foo) bar: 11))) +(#<procedure #2> (bar: 11)) + |
(keyword-expected-exception? obj) | procedure |
(keyword-expected-exception-procedure exc) | procedure |
(keyword-expected-exception-arguments exc) | procedure |
Keyword-expected-exception objects are raised when a procedure +accepting keyword arguments is called and a nonkeyword was supplied +where a keyword was expected. The parameter exc must be an +keyword-expected-exception object. +
+The procedure keyword-expected-exception? returns
+#t when obj is an keyword-expected-exception
+object and #f otherwise.
+
The procedure keyword-expected-exception-procedure
+returns the procedure that raised exc.
+
The procedure keyword-expected-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
For example: +
+> (define (handler exc) + (if (keyword-expected-exception? exc) + (list (keyword-expected-exception-procedure exc) + (keyword-expected-exception-arguments exc)) + 'not-keyword-expected-exception)) +> (with-exception-catcher + handler + (lambda () ((lambda (#!key (foo 5)) foo) 11 22))) +(#<procedure #2> (11 22)) + |
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+ |
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+ |
+ |
+ |
+ |
+ |
+
(error-exception? obj) | procedure |
(error-exception-message exc) | procedure |
(error-exception-parameters exc) | procedure |
(error message obj…) | procedure |
Error-exception objects are raised when the error procedure is
+called. The parameter exc must be an error-exception
+object.
+
The procedure error-exception? returns
+#t when obj is an error-exception
+object and #f otherwise.
+
The procedure error-exception-message returns the first
+argument of the call to error that raised exc.
+
The procedure error-exception-parameters returns the list of
+arguments, starting with the second argument, of the call to
+error that raised exc.
+
The error procedure raises an error-exception object whose
+message field is message and parameters field is the list of
+values obj….
+
For example: +
+> (define (handler exc)
+ (if (error-exception? exc)
+ (list (error-exception-message exc)
+ (error-exception-parameters exc))
+ 'not-error-exception))
+> (with-exception-catcher
+ handler
+ (lambda () (error "unexpected object:" 123)))
+("unexpected object:" (123))
+ |
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+ |
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+ |
+ |
+ |
+ |
+ |
+
The host environment is the set of resources, such as the filesystem, +network and processes, that are managed by the operating system within +which the Scheme program is executing. This chapter specifies how the +host environment can be accessed from within the Scheme program. +
+In this chapter we say that the Scheme program being executed is a +process, even though the concept of process does not exist in some +operating systems supported by Gambit (e.g. MSDOS). +
+ |
+ |
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+ |
+ |
+ |
+ |
+ |
+
Gambit uses a naming convention for files that is compatible with +the one used by the host environment but extended to allow +referring to the home directory of the current user or some +specific user and the installation directories. +
+A path is a string that denotes a file, for example
+"src/readme.txt". Each component of a path is separated by a
+/ under UNIX and Mac OS X and by a / or \ under
+MSDOS and Microsoft Windows. A leading separator indicates an
+absolute path under UNIX, Mac OS X, MSDOS and Microsoft Windows. A
+path which does not contain a path separator is relative to the
+current working directory on all operating systems. A volume
+specifier such as C: may prefix a file name under MSDOS and
+Microsoft Windows.
+
A path which starts with the characters ~~ denotes a file in an +installation directory. If nothing follows the ~~ then the +directory denoted is the central installation directory. Otherwise +what follows the ~~ is the name of the installation directory, +for example ~~lib denotes the lib installation +directory. Note that the location of the installation directories may +be overridden by using the -:=DIRECTORY and +-:~~DIR=DIRECTORY runtime options or by defining +the GAMBCOPT environment variable. +
+ +A path which starts with the character ~ not followed by +~ denotes a file in the user’s home directory. The user’s home +directory is contained in the HOME environment variable under +UNIX, Mac OS X, MSDOS and Microsoft Windows. Under MSDOS and +Microsoft Windows, if the HOME environment variable is not +defined, the environment variables HOMEDRIVE and +HOMEPATH are concatenated if they are defined. If this fails +to yield a home directory, the central installation directory is used +instead. +
+ +A path which starts with the characters ~username +denotes a file in the home directory of the given user. Under UNIX +and Mac OS X this is found using the password file. There is no +equivalent under MSDOS and Microsoft Windows. +
+ (current-directory [new-current-directory]) | procedure |
The parameter object current-directory is bound to the current
+working directory. Calling this procedure with no argument returns
+the absolute normalized path of the directory and calling this
+procedure with one argument sets the directory to
+new-current-directory. The initial binding of this parameter
+object is the current working directory of the current process. The
+path returned by current-directory always contains a trailing
+directory separator. Modifications of the parameter object do not
+change the current working directory of the current process (i.e.
+that is accessible with the UNIX getcwd() function and the
+Microsoft Windows GetCurrentDirectory function). It is an
+error to mutate the string returned by current-directory.
+
For example under UNIX: +
+> (current-directory) +"/Users/feeley/gambit/doc/" +> (current-directory "..") +> (current-directory) +"/Users/feeley/gambit/" +> (path-expand "foo" "~~") +"/usr/local/Gambit-C/foo" +> (parameterize ((current-directory "~~")) (path-expand "foo")) +"/usr/local/Gambit-C/foo" + |
(path-expand path [origin-directory]) | procedure |
The procedure path-expand takes the path of a file or directory
+and returns an expanded path, which is an absolute path when
+path or origin-directory are absolute paths.
+The optional origin-directory parameter, which defaults
+to the current working directory, is the directory used to resolve
+relative paths. Components of the paths path and
+origin-directory need not exist.
+
For example under UNIX: +
+> (path-expand "foo") +"/Users/feeley/gambit/doc/foo" +> (path-expand "~/foo") +"/Users/feeley/foo" +> (path-expand "~~lib/foo") +"/usr/local/Gambit-C/lib/foo" +> (path-expand "../foo") +"/Users/feeley/gambit/doc/../foo" +> (path-expand "foo" "") +"foo" +> (path-expand "foo" "/tmp") +"/tmp/foo" +> (path-expand "this/file/does/not/exist") +"/Users/feeley/gambit/doc/this/file/does/not/exist" +> (path-expand "") +"/Users/feeley/gambit/doc/" + |
(path-normalize path [allow-relative? [origin-directory]]) | procedure |
The procedure path-normalize takes a path of a file or
+directory and returns its normalized path. The optional
+origin-directory parameter, which defaults to the current
+working directory, is the directory used to resolve relative paths.
+All components of the paths path and
+origin-directory must exist, except possibly the last
+component of path. A normalized path is a path
+containing no redundant parts and which is consistent with the current
+structure of the filesystem. A normalized path of a directory will
+always end with a path separator (i.e. /, \, or :
+depending on the operating system). The optional
+allow-relative? parameter, which defaults to #f,
+indicates if the path returned can be expressed relatively to
+origin-directory: a #f requests an absolute path,
+the symbol shortest requests the shortest of the absolute and
+relative paths, and any other value requests the relative path. The
+shortest path is useful for interaction with the user because short
+relative paths are typically easier to read than long absolute paths.
+
For example under UNIX: +
+> (path-expand "../foo") +"/Users/feeley/gambit/doc/../foo" +> (path-normalize "../foo") +"/Users/feeley/gambit/foo" +> (path-normalize "this/file/does/not/exist") +*** ERROR IN (console)@3.1 -- No such file or directory +(path-normalize "this/file/does/not/exist") + |
(path-extension path) | procedure |
(path-strip-extension path) | procedure |
(path-directory path) | procedure |
(path-strip-directory path) | procedure |
(path-strip-trailing-directory-separator path) | procedure |
(path-volume path) | procedure |
(path-strip-volume path) | procedure |
These procedures extract various parts of a path, which need not be a
+normalized path. The procedure path-extension returns the file
+extension (including the period) or the empty string if there is no
+extension. The procedure path-strip-extension returns the path
+with the extension stripped off. The procedure path-directory
+returns the file’s directory (including the last path separator) or
+the empty string if no directory is specified in the path. The
+procedure path-strip-directory returns the path with the
+directory stripped off. The procedure
+path-strip-trailing-directory-separator returns the path with
+the directory separator stripped off if one is at the end of the path.
+The procedure path-volume returns the file’s volume (including
+the last path separator) or the empty string if no volume is specified
+in the path. The procedure path-strip-volume returns the path
+with the volume stripped off.
+
For example under UNIX: +
+> (path-extension "/tmp/foo") +"" +> (path-extension "/tmp/foo.txt") +".txt" +> (path-strip-extension "/tmp/foo.txt") +"/tmp/foo" +> (path-directory "/tmp/foo.txt") +"/tmp/" +> (path-strip-directory "/tmp/foo.txt") +"foo.txt" +> (path-strip-trailing-directory-separator "/usr/local/bin/") +"/usr/local/bin" +> (path-strip-trailing-directory-separator "/usr/local/bin") +"/usr/local/bin" +> (path-volume "/tmp/foo.txt") +"" +> (path-volume "C:/tmp/foo.txt") +"" ; result is "C:" under Microsoft Windows +> (path-strip-volume "C:/tmp/foo.txt") +"C:/tmp/foo.txt" ; result is "/tmp/foo.txt" under Microsoft Windows + |
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+ |
+ |
+ |
+ |
+ |
+
(create-directory path-or-settings) | procedure |
This procedure creates a directory. The argument
+path-or-settings is either a string denoting a filesystem path
+or a list of port settings which must contain a path: setting.
+Here are the settings allowed:
+
path: string
+
+This setting indicates the location of the directory to create in the +filesystem. There is no default value for this setting. +
+permissions: 12-bit-exact-integer
+
+This setting controls the UNIX permissions that will be attached to
+the file if it is created. The default value of this setting is
+#o777.
+
For example: +
+> (create-directory "newdir") +> (create-directory "newdir") +*** ERROR IN (console)@2.1 -- File exists +(create-directory "newdir") + |
(create-fifo path-or-settings) | procedure |
This procedure creates a FIFO. The argument path-or-settings is
+either a string denoting a filesystem path or a list of port settings
+which must contain a path: setting. Here are the settings
+allowed:
+
path: string
+
+This setting indicates the location of the FIFO to create in the +filesystem. There is no default value for this setting. +
+permissions: 12-bit-exact-integer
+
+This setting controls the UNIX permissions that will be attached to
+the file if it is created. The default value of this setting is
+#o666.
+
For example: +
+> (create-fifo "fifo") +> (define a (open-input-file "fifo")) +> (define b (open-output-file "fifo")) +> (display "1 22 333" b) +> (force-output b) +> (read a) +1 +> (read a) +22 + |
(create-link source-path destination-path) | procedure |
This procedure creates a hard link between source-path and +destination-path. The argument source-path must be a +string denoting the path of an existing file. The argument +destination-path must be a string denoting the path of the link +to create. +
+ + + (create-symbolic-link source-path destination-path) | procedure |
This procedure creates a symbolic link between source-path and +destination-path. The argument source-path must be a +string denoting the path of an existing file. The argument +destination-path must be a string denoting the path of the +symbolic link to create. +
+ + + (rename-file source-path destination-path) | procedure |
This procedure renames the file source-path to +destination-path. The argument source-path must be a +string denoting the path of an existing file. The argument +destination-path must be a string denoting the new path of the +file. +
+ + + (copy-file source-path destination-path) | procedure |
This procedure copies the file source-path to +destination-path. The argument source-path must be a +string denoting the path of an existing file. The argument +destination-path must be a string denoting the path of the +file to create. +
+ + + (delete-file path) | procedure |
This procedure deletes the file path. The argument path +must be a string denoting the path of an existing file. +
+ + + (delete-directory path) | procedure |
This procedure deletes the directory path. The argument +path must be a string denoting the path of an existing +directory. +
+ + + (directory-files [path-or-settings]) | procedure |
This procedure returns the list of the files in a directory. The
+argument path-or-settings is either a string denoting a
+filesystem path to a directory or a list of settings which must
+contain a path: setting. If it is not specified,
+path-or-settings defaults to the current directory (the value
+bound to the current-directory parameter object). Here are the
+settings allowed:
+
path: string
+
+This setting indicates the location of the directory in the filesystem. +There is no default value for this setting. +
+ignore-hidden: ( #f | #t | dot-and-dot-dot )
+
+This setting controls whether hidden-files will be returned. Under
+UNIX and Mac OS X hidden-files are those that start with a period
+(such as ., .., and .profile). Under Microsoft
+Windows hidden files are the . and .. entries and the
+files whose “hidden file” attribute is set. A setting of #f
+will enumerate all the files. A setting of #t will only
+enumerate the files that are not hidden. A setting of
+dot-and-dot-dot will enumerate all the files except for the
+. and .. hidden files. The default value of this
+setting is #t.
+
For example: +
+> (directory-files)
+("complex" "README" "simple")
+> (directory-files "../include")
+("config.h" "config.h.in" "gambit.h" "makefile" "makefile.in")
+> (directory-files (list path: "../include" ignore-hidden: #f))
+("." ".." "config.h" "config.h.in" "gambit.h" "makefile" "makefile.in")
+ |
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+ |
+ |
+ |
+ |
+ |
+
(shell-command command) | procedure |
The procedure shell-command calls up the shell to execute
+command which must be a string. This procedure returns
+the exit status of the shell in the form that the C library’s
+system routine returns.
+
For example under UNIX: +
+> (shell-command "ls -sk f*.scm") +4 fact.scm 4 fib.scm +0 + |
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+ |
+ |
+ |
+ |
+ |
+
(exit [status]) | procedure |
The procedure exit causes the process to terminate with the
+status status which must be an exact integer in the range 0 to
+255. If it is not specified, status defaults to 0.
+
For example under UNIX: +
+$ gsi +Gambit v4.6.1 + +> (exit 42) +$ echo $? +42 + |
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+ |
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+ |
+ |
+ |
+ |
+ |
+
(command-line) | procedure |
This procedure returns a list of strings corresponding to the command
+line arguments, including the program file name as the first element
+of the list. When the interpreter executes a Scheme script, the list
+returned by command-line contains the script’s absolute path
+followed by the remaining command line arguments.
+
For example under UNIX: +
+$ gsi -:d -e "(pretty-print (command-line))"
+("gsi" "-e" "(pretty-print (command-line))")
+$ cat foo
+#!/usr/local/Gambit-C/bin/gsi-script
+(pretty-print (command-line))
+$ ./foo 1 2 "3 4"
+("/u/feeley/./foo" "1" "2" "3 4")
+ |
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+ |
+ |
+ |
+ |
+ |
+
(getenv name [default]) | procedure |
(setenv name [new-value]) | procedure |
The procedure getenv returns the value of the environment
+variable name of the current process. Variable names are
+denoted with strings. A string is returned if the environment
+variable is bound, otherwise default is returned if it is
+specified, otherwise an exception is raised.
+
The procedure setenv changes the binding of the environment
+variable name to new-value which must be a string.
+If new-value is not specified the binding is removed.
+
For example under UNIX: +
+> (getenv "HOME") +"/Users/feeley" +> (getenv "DOES_NOT_EXIST" #f) +#f +> (setenv "DOES_NOT_EXIST" "it does now") +> (getenv "DOES_NOT_EXIST" #f) +"it does now" +> (setenv "DOES_NOT_EXIST") +> (getenv "DOES_NOT_EXIST" #f) +#f +> (getenv "DOES_NOT_EXIST") +*** ERROR IN (console)@7.1 -- Unbound OS environment variable +(getenv "DOES_NOT_EXIST") + |
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+ |
+ |
+ |
+ |
+ |
+
Procedures are available for measuring real time (aka “wall” time) +and cpu time (the amount of time the cpu has been executing the +process). The resolution of the real time and cpu time clock is +operating system dependent. Typically the resolution of the cpu time +clock is rather coarse (measured in “ticks” of 1/60th or 1/100th of +a second). Real time is internally computed relative to some +arbitrary point in time using floating point numbers, which means that +there is a gradual loss of resolution as time elapses. Moreover, some +operating systems report time in number of ticks using a 32 bit +integer so the value returned by the time related procedures may +wraparound much before any significant loss of resolution occurs (for +example 2.7 years if ticks are 1/50th of a second). +
+ (current-time) | procedure |
(time? obj) | procedure |
(time->seconds time) | procedure |
(seconds->time x) | procedure |
The procedure current-time returns a time object
+representing the current point in real time.
+
The procedure time? returns #t when obj is a time
+object and #f otherwise.
+
The procedure time->seconds converts the time object time
+into an inexact real number representing the number of seconds elapsed
+since the “epoch” (which is 00:00:00 Coordinated Universal Time
+01-01-1970).
+
The procedure seconds->time converts the real number x
+representing the number of seconds elapsed since the “epoch” into a
+time object.
+
For example: +
+> (current-time)
+#<time #2>
+> (time? (current-time))
+#t
+> (time? 123)
+#f
+> (time->seconds (current-time))
+1083118758.63973
+> (time->seconds (current-time))
+1083118759.909163
+> (seconds->time (+ 10 (time->seconds (current-time))
+#<time #3> ; a time object representing 10 seconds in the future
+ |
(process-times) | procedure |
(cpu-time) | procedure |
(real-time) | procedure |
The procedure process-times returns a three element f64vector
+containing the cpu time that has been used by the program and the real
+time that has elapsed since it was started. The first element
+corresponds to “user” time in seconds, the second element
+corresponds to “system” time in seconds and the third element is the
+elapsed real time in seconds. On operating systems that can’t
+differentiate user and system time, the system time is zero. On
+operating systems that can’t measure cpu time, the user time is equal
+to the elapsed real time and the system time is zero.
+
The procedure cpu-time returns the cpu time in seconds that has
+been used by the program (user time plus system time).
+
The procedure real-time returns the real time that has elapsed
+since the program was started.
+
For example: +
+> (process-times) +#f64(.02794 .021754 .159926176071167) +> (cpu-time) +.051223 +> (real-time) +.40660619735717773 + |
(time expr) | special form |
The time special form evaluates expr and returns the
+result. As a side effect it displays a message on the interaction
+channel which indicates how long the evaluation took (in real time and
+cpu time), how much time was spent in the garbage collector, how much
+memory was allocated during the evaluation and how many minor and
+major page faults occured (0 is reported if not running under UNIX).
+
For example: +
+> (define (f x) + (let loop ((x x) (lst '())) + (if (= x 0) + lst + (loop (- x 1) (cons x lst))))) +> (length (time (f 100000))) +(time (f 100000)) + 683 ms real time + 558 ms cpu time (535 user, 23 system) + 8 collections accounting for 102 ms real time (70 user, 5 system) + 6400160 bytes allocated + no minor faults + no major faults +100000 + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(file-exists? path [chase?]) | procedure |
The path argument must be a string. This procedure returns
+#t when a file by that name exists, and returns #f
+otherwise.
+
When chase? is present and #f, symbolic links will not be
+chased, in other words if path refers to a symbolic link,
+file-exists? will return #t whether or not it points to
+an existing file.
+
For example: +
+> (file-exists? "nofile") +#f + |
(file-info path [chase?]) | procedure |
This procedure accesses the filesystem to get information about the +file whose location is given by the string path. A +file-information record is returned that contains the file’s type, the +device number, the inode number, the mode (permission bits), the +number of links, the file’s user id, the file’s group id, the file’s +size in bytes, the times of last-access, last-modification and +last-change, the attributes, and the creation time. +
+When chase? is present and #f, symbolic links will not be
+chased, in other words if path refers to a symbolic link the
+file-info procedure will return information about the link
+rather than the file it links to.
+
For example: +
+> (file-info "/dev/tty") +#<file-info #2 + type: character-special + device: 19513156 + inode: 20728196 + mode: 438 + number-of-links: 1 + owner: 0 + group: 0 + size: 0 + last-access-time: #<time #3> + last-modification-time: #<time #4> + last-change-time: #<time #5> + attributes: 128 + creation-time: #<time #6>> + |
(file-info? obj) | procedure |
This procedure returns #t when obj is a file-information
+record and #f otherwise.
+
For example: +
+> (file-info? (file-info "/dev/tty")) +#t +> (file-info? 123) +#f + |
(file-info-type file-info) | procedure |
Returns the type field of the file-information record +file-info. The type is denoted by a symbol. +The following types are possible: +
+regularRegular file +
directoryDirectory +
character-specialCharacter special device +
block-specialBlock special device +
fifoFIFO +
symbolic-linkSymbolic link +
socketSocket +
unknownFile is of an unknown type +
For example: +
+> (file-info-type (file-info "/dev/tty")) +character-special +> (file-info-type (file-info "/dev")) +directory + |
(file-info-device file-info) | procedure |
Returns the device field of the file-information record +file-info. +
+For example: +
+> (file-info-device (file-info "/dev/tty")) +19513156 + |
(file-info-inode file-info) | procedure |
Returns the inode field of the file-information record +file-info. +
+For example: +
+> (file-info-inode (file-info "/dev/tty")) +20728196 + |
(file-info-mode file-info) | procedure |
Returns the mode field of the file-information record +file-info. +
+For example: +
+> (file-info-mode (file-info "/dev/tty")) +438 + |
(file-info-number-of-links file-info) | procedure |
Returns the number-of-links field of the file-information record +file-info. +
+For example: +
+> (file-info-number-of-links (file-info "/dev/tty")) +1 + |
(file-info-owner file-info) | procedure |
Returns the owner field of the file-information record +file-info. +
+For example: +
+> (file-info-owner (file-info "/dev/tty")) +0 + |
(file-info-group file-info) | procedure |
Returns the group field of the file-information record +file-info. +
+For example: +
+> (file-info-group (file-info "/dev/tty")) +0 + |
(file-info-size file-info) | procedure |
Returns the size field of the file-information record +file-info. +
+For example: +
+> (file-info-size (file-info "/dev/tty")) +0 + |
(file-info-last-access-time file-info) | procedure |
Returns the last-access-time field of the file-information record +file-info. +
+For example: +
+> (file-info-last-access-time (file-info "/dev/tty")) +#<time #2> + |
(file-info-last-modification-time file-info) | procedure |
Returns the last-modification-time field of the file-information record +file-info. +
+For example: +
+> (file-info-last-modification-time (file-info "/dev/tty")) +#<time #2> + |
(file-info-last-change-time file-info) | procedure |
Returns the last-change-time field of the file-information record +file-info. +
+For example: +
+> (file-info-last-change-time (file-info "/dev/tty")) +#<time #2> + |
(file-info-attributes file-info) | procedure |
Returns the attributes field of the file-information record +file-info. +
+For example: +
+> (file-info-attributes (file-info "/dev/tty")) +128 + |
(file-info-creation-time file-info) | procedure |
Returns the creation-time field of the file-information record +file-info. +
+For example: +
+> (file-info-creation-time (file-info "/dev/tty")) +#<time #2> + |
(file-type path) | procedure |
(file-device path) | procedure |
(file-inode path) | procedure |
(file-mode path) | procedure |
(file-number-of-links path) | procedure |
(file-owner path) | procedure |
(file-group path) | procedure |
(file-size path) | procedure |
(file-last-access-time path) | procedure |
(file-last-modification-time path) | procedure |
(file-last-change-time path) | procedure |
(file-attributes path) | procedure |
(file-creation-time path) | procedure |
These procedures combine a call to the file-info procedure and
+a call to a file-information record field accessor. For instance
+(file-type path) is equivalent to (file-info-type
+(file-info path)).
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(group-info group-name-or-id) | procedure |
This procedure accesses the group database to get information about the +group identified by group-name-or-id, which is the group’s symbolic +name (string) or the group’s GID (exact integer). A group-information +record is returned that contains the group’s symbolic name, the group’s +id (GID), and the group’s members (list of symbolic user names). +
+For example: +
+> (group-info "staff")
+#<group-info #2 name: "staff" gid: 20 members: ("root")>
+> (group-info 29)
+#<group-info #3
+ name: "certusers"
+ gid: 29
+ members: ("root" "jabber" "postfix" "cyrusimap")>
+> (group-info 5000)
+*** ERROR IN (console)@3.1 -- Resource temporarily unavailable
+(group-info 5000)
+ |
(group-info? obj) | procedure |
This procedure returns #t when obj is a group-information
+record and #f otherwise.
+
For example: +
+> (group-info? (group-info "daemon")) +#t +> (group-info? 123) +#f + |
(group-info-name group-info) | procedure |
Returns the symbolic name field of the group-information record +group-info. +
+For example: +
+> (group-info-name (group-info 29)) +"certusers" + |
(group-info-gid group-info) | procedure |
Returns the group id field of the group-information record +group-info. +
+For example: +
+> (group-info-gid (group-info "staff")) +20 + |
(group-info-members group-info) | procedure |
Returns the members field of the group-information record +group-info. +
+For example: +
+> (group-info-members (group-info "staff"))
+("root")
+ |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(user-name) | procedure |
This procedure returns the user’s name as a string. +
+For example: +
+> (user-name) +"feeley" + |
(user-info user-name-or-id) | procedure |
This procedure accesses the user database to get information about the +user identified by user-name-or-id, which is the user’s symbolic +name (string) or the user’s UID (exact integer). A user-information +record is returned that contains the user’s symbolic name, the user’s +id (UID), the user’s group id (GID), the path to the user’s home +directory, and the user’s login shell. +
+For example: +
+> (user-info "feeley") +#<user-info #2 + name: "feeley" + uid: 506 + gid: 506 + home: "/Users/feeley" + shell: "/bin/bash"> +> (user-info 0) +#<user-info #3 name: "root" uid: 0 gid: 0 home: "/var/root" shell: "/bin/sh"> +> (user-info 5000) +*** ERROR IN (console)@3.1 -- Resource temporarily unavailable +(user-info 5000) + |
(user-info? obj) | procedure |
This procedure returns #t when obj is a user-information
+record and #f otherwise.
+
For example: +
+> (user-info? (user-info "feeley")) +#t +> (user-info? 123) +#f + |
(user-info-name user-info) | procedure |
Returns the symbolic name field of the user-information record +user-info. +
+For example: +
+> (user-info-name (user-info 0)) +"root" + |
(user-info-uid user-info) | procedure |
Returns the user id field of the user-information record +user-info. +
+For example: +
+> (user-info-uid (user-info "feeley")) +506 + |
(user-info-gid user-info) | procedure |
Returns the group id field of the user-information record +user-info. +
+For example: +
+> (user-info-gid (user-info "feeley")) +506 + |
(user-info-home user-info) | procedure |
Returns the home directory field of the user-information record +user-info. +
+For example: +
+> (user-info-home (user-info 0)) +"/var/root" + |
(user-info-shell user-info) | procedure |
Returns the shell field of the user-information record +user-info. +
+For example: +
+> (user-info-shell (user-info 0)) +"/bin/sh" + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(host-name) | procedure |
This procedure returns the machine’s host name as a string. +
+For example: +
+> (host-name) +"mega.iro.umontreal.ca" + |
(host-info host-name) | procedure |
This procedure accesses the internet host database to get information +about the machine whose name is denoted by the string host-name. +A host-information record is returned that contains the official name +of the machine, a list of aliases (alternative names), and a non-empty +list of IP addresses for this machine. An exception is raised when +host-name does not appear in the database. +
+For example: +
+> (host-info "www.google.com")
+#<host-info #2
+ name: "www.l.google.com"
+ aliases: ("www.google.com")
+ addresses: (#u8(66 249 85 99) #u8(66 249 85 104))>
+> (host-info "unknown.domain")
+*** ERROR IN (console)@2.1 -- Unknown host
+(host-info "unknown.domain")
+ |
(host-info? obj) | procedure |
This procedure returns #t when obj is a host-information
+record and #f otherwise.
+
For example: +
+> (host-info? (host-info "www.google.com")) +#t +> (host-info? 123) +#f + |
(host-info-name host-info) | procedure |
Returns the official name field of the host-information record +host-info. +
+For example: +
+> (host-info-name (host-info "www.google.com")) +"www.l.google.com" + |
(host-info-aliases host-info) | procedure |
Returns the aliases field of the host-information record +host-info. This field is a possibly empty list of strings. +
+For example: +
+> (host-info-aliases (host-info "www.google.com"))
+("www.google.com")
+ |
(host-info-addresses host-info) | procedure |
Returns the addresses field of the host-information record +host-info. This field is a non-empty list of u8vectors +denoting IP addresses. +
+For example: +
+> (host-info-addresses (host-info "www.google.com")) +(#u8(66 249 85 99) #u8(66 249 85 104)) + |
(address-infos [host: host] [service: service] [family: family] [socket-type: socket-type] [protocol: protocol]) | procedure |
This procedure is an interface to the getaddrinfo system call.
+It accesses the internet host database to get information about the
+machine whose name is denoted by the string host and service is
+denoted by the string service and network address family is
+family (INET or INET6) and network socket-type is
+socket-type (STREAM or DGRAM or RAW) and
+network protocol is socket-type (TCP or UDP). A
+list of address-information records is returned.
+
For example: +
+> (address-infos host: "ftp.at.debian.org") +(#<address-info #2 + family: INET6 + socket-type: DGRAM + protocol: UDP + socket-info: + #<socket-info #3 + family: INET6 + port-number: 0 + address: #u16(8193 2136 2 1 0 0 0 16)>> + #<address-info #4 + family: INET6 + socket-type: STREAM + protocol: TCP + socket-info: + #<socket-info #5 + family: INET6 + port-number: 0 + address: #u16(8193 2136 2 1 0 0 0 16)>> + #<address-info #6 + family: INET + socket-type: DGRAM + protocol: UDP + socket-info: + #<socket-info #7 + family: INET + port-number: 0 + address: #u8(213 129 232 18)>> + #<address-info #8 + family: INET + socket-type: STREAM + protocol: TCP + socket-info: + #<socket-info #9 + family: INET + port-number: 0 + address: #u8(213 129 232 18)>>) +> (address-infos host: "ftp.at.debian.org" + family: 'INET + protocol: 'TCP) +(#<address-info #10 + family: INET + socket-type: STREAM + protocol: TCP + socket-info: + #<socket-info #11 + family: INET + port-number: 0 + address: #u8(213 129 232 18)>>) +> (address-infos host: "unknown.domain") +*** ERROR IN (console)@5.1 -- nodename nor servname provided, or not known +(address-infos host: "unknown.domain") + |
(address-info? obj) | procedure |
This procedure returns #t when obj is an address-information
+record and #f otherwise.
+
For example: +
+> (map address-info? + (address-infos host: "ftp.at.debian.org")) +(#t #t #t #t) +> (address-info? 123) +#f + |
(address-info-family address-info) | procedure |
Returns the family field of the address-information record +address-info. +
+For example: +
+> (map address-info-family + (address-infos host: "ftp.at.debian.org")) +(INET6 INET6 INET INET) + |
(address-info-socket-type address-info) | procedure |
Returns the socket-type field of the address-information record +address-info. +
+For example: +
+> (map address-info-socket-type + (address-infos host: "ftp.at.debian.org")) +(DGRAM STREAM DGRAM STREAM) + |
(address-info-protocol address-info) | procedure |
Returns the protocol field of the address-information record +address-info. +
+For example: +
+> (map address-info-protocol + (address-infos host: "ftp.at.debian.org")) +(UDP TCP UDP TCP) + |
(address-info-socket-info address-info) | procedure |
Returns the socket-info field of the address-information record +address-info. +
+For example: +
+> (map address-info-socket-info + (address-infos host: "ftp.at.debian.org")) +(#<socket-info #2 + family: INET6 + port-number: 0 + address: #u16(8193 2136 2 1 0 0 0 16)> + #<socket-info #3 + family: INET6 + port-number: 0 + address: #u16(8193 2136 2 1 0 0 0 16)> + #<socket-info #4 + family: INET + port-number: 0 + address: #u8(213 129 232 18)> + #<socket-info #5 + family: INET + port-number: 0 + address: #u8(213 129 232 18)>) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(service-info service-name-or-id) | procedure |
This procedure accesses the service database to get information about +the service identified by service-name-or-id, which is the +service’s symbolic name (string) or the service’s port number (exact +integer). A service-information record is returned that contains the +service’s symbolic name, a list of aliases (alternative names), the +port number (exact integer), and the protocol name (string). An +exception is raised when service-name-or-id does not appear in +the database. +
+For example: +
+> (service-info "http")
+#<service-info #2
+ name: "http"
+ aliases: ("www" "www-http")
+ port-number: 80
+ protocol: "udp">
+> (service-info 80)
+#<service-info #3
+ name: "http"
+ aliases: ("www" "www-http")
+ port-number: 80
+ protocol: "udp">
+ |
(service-info? obj) | procedure |
This procedure returns #t when obj is a service-information
+record and #f otherwise.
+
For example: +
+> (service-info? (service-info "http")) +#t +> (service-info? 123) +#f + |
(service-info-name service-info) | procedure |
Returns the symbolic name field of the service-information record +service-info. +
+For example: +
+> (service-info-name (service-info 80)) +"http" + |
(service-info-aliases service-info) | procedure |
Returns the aliases field of the service-information record +service-info. This field is a possibly empty list of strings. +
+For example: +
+> (service-info-aliases (service-info "http"))
+("www" "www-http")
+ |
(service-info-port-number service-info) | procedure |
Returns the service port number field of the service-information +record service-info. +
+For example: +
+> (service-info-port-number (service-info "http")) +80 + |
(service-info-protocol service-info) | procedure |
Returns the service protocol name field of the service-information +record service-info. +
+For example: +
+> (service-info-protocol (service-info "http")) +"udp" + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(protocol-info protocol-name-or-id) | procedure |
This procedure accesses the protocol database to get information about +the protocol identified by protocol-name-or-id, which is the +protocol’s symbolic name (string) or the protocol’s number (exact +integer). A protocol-information record is returned that contains the +protocol’s symbolic name, a list of aliases (alternative names), and +the protocol number (32 bit unsigned exact integer). An exception is +raised when protocol-name-or-id does not appear in the database. +
+For example: +
+> (protocol-info "tcp")
+#<protocol-info #2 name: "tcp" aliases: ("TCP") number: 6>
+> (protocol-info 6)
+#<protocol-info #2 name: "tcp" aliases: ("TCP") number: 6>
+ |
(protocol-info? obj) | procedure |
This procedure returns #t when obj is a protocol-information
+record and #f otherwise.
+
For example: +
+> (protocol-info? (protocol-info "tcp")) +#t +> (protocol-info? 123) +#f + |
(protocol-info-name protocol-info) | procedure |
Returns the symbolic name field of the protocol-information record +protocol-info. +
+For example: +
+> (protocol-info-name (protocol-info 6)) +"tcp" + |
(protocol-info-aliases protocol-info) | procedure |
Returns the aliases field of the protocol-information record +protocol-info. This field is a possibly empty list of strings. +
+For example: +
+> (protocol-info-aliases (protocol-info "tcp"))
+("TCP")
+ |
(protocol-info-number protocol-info) | procedure |
Returns the protocol number field of the protocol-information record +protocol-info. +
+For example: +
+> (protocol-info-number (protocol-info "tcp")) +6 + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(network-info network-name-or-id) | procedure |
This procedure accesses the network database to get information about +the network identified by network-name-or-id, which is the +network’s symbolic name (string) or the network’s number (exact +integer). A network-information record is returned that contains the +network’s symbolic name, a list of aliases (alternative names), and +the network number (32 bit unsigned exact integer). An exception is +raised when network-name-or-id does not appear in the database. +
+For example: +
+> (network-info "loopback")
+#<network-info #2
+ name: "loopback"
+ aliases: ("loopback-net")
+ number: 127>
+> (network-info 127)
+#<network-info #3
+ name: "loopback"
+ aliases: ("loopback-net")
+ number: 127>
+ |
(network-info? obj) | procedure |
This procedure returns #t when obj is a network-information
+record and #f otherwise.
+
For example: +
+> (network-info? (network-info "loopback")) +#t +> (network-info? 123) +#f + |
(network-info-name network-info) | procedure |
Returns the symbolic name field of the network-information record +network-info. +
+For example: +
+> (network-info-name (network-info 127)) +"loopback" + |
(network-info-aliases network-info) | procedure |
Returns the aliases field of the network-information record +network-info. This field is a possibly empty list of strings. +
+For example: +
+> (network-info-aliases (network-info "loopback"))
+("loopback-net")
+ |
(network-info-number network-info) | procedure |
Returns the network number field of the network-information record +network-info. +
+For example: +
+> (network-info-number (network-info "loopback")) +127 + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
Unidirectional ports allow communication between a producer of +information and a consumer. An input-port’s producer is typically a +resource managed by the operating system (such as a file, a process or +a network connection) and the consumer is the Scheme program. The +roles are reversed for an output-port. +
+Associated with each port are settings that affect I/O operations on +that port (encoding of characters to bytes, end-of-line encoding, type +of buffering, etc). Port settings are specified when the port is +created. Some port settings can be changed after a port is created. +
+Bidirectional ports, also called input-output-ports, allow +communication in both directions. They are best viewed as an object +that groups two separate unidirectional ports (one in each direction). +Each direction has its own port settings and can be closed +independently from the other direction. +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The four classes of ports listed below form an inheritance hierarchy. +Operations possible for a certain class of port are also possible for +the subclasses. Only device-ports are connected to a device managed +by the operating system. For instance it is possible to create ports +that behave as a FIFO where the Scheme program is both the producer +and consumer of information (possibly one thread is the producer and +another thread is the consumer). +
+#\newline will be encoded as the 2 bytes CR-LF when using
+ISO-8859-1 character encoding and cr-lf end-of-line encoding, and
+a non-ASCII character will generate more than 1 byte when using UTF-8
+character encoding). When reading a character, a similar decoding
+occurs.
+
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
Some port settings are only valid for specific port classes whereas
+some others are valid for all ports. Port settings are specified when
+a port is created. The settings that are not specified will default
+to some reasonable values. Keyword objects are used to name the
+settings to be set. As a simple example, a device-port connected to
+the file "foo" can be created using the call
+
(open-input-file "foo") + |
This will use default settings for the character encoding, buffering, +etc. If the UTF-8 character encoding is desired, then the port could +be opened using the call +
+(open-input-file (list path: "foo" char-encoding: 'UTF-8)) + |
Here the argument of the procedure open-input-file has been
+replaced by a port settings list which specifies the value of
+each port setting that should not be set to the default value. Note
+that some port settings have no useful default and it is therefore
+required to specify a value for them, such as the path: in the
+case of the file opening procedures. All port creation procedures
+(i.e. named open-...) take a single argument that can either
+be a port settings list or a value of a type that depends on the kind
+of port being created (a path string for files, an IP port number for
+socket servers, etc).
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
| 17.4.1 Object-port settings | ||
| 17.4.2 Object-port operations |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The following is a list of port settings that are valid for all types +of ports. +
+direction: ( input | output | input-output )
+
+This setting controls the direction of the port. The symbol
+input indicates a unidirectional input-port, the symbol
+output indicates a unidirectional output-port, and the symbol
+input-output indicates a bidirectional port. The default
+value of this setting depends on the port creation procedure.
+
buffering: ( #f | #t | line )
+
+This setting controls the buffering of the port. To set each
+direction separately the keywords input-buffering: and
+output-buffering: must be used instead of buffering:.
+The value #f selects unbuffered I/O, the value #t
+selects fully buffered I/O, and the symbol line selects line
+buffered I/O (the output buffer is drained when a #\newline
+character is written). Line buffered I/O only applies to
+character-ports. The default value of this setting is operating
+system dependent except consoles which are unbuffered.
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(input-port? obj) | procedure |
(output-port? obj) | procedure |
(port? obj) | procedure |
The procedure input-port? returns #t when obj is a
+unidirectional input-port or a bidirectional port and #f
+otherwise.
+
The procedure output-port? returns #t when obj is a
+unidirectional output-port or a bidirectional port and #f
+otherwise.
+
The procedure port? returns #t when obj is a port
+(either unidirectional or bidirectional) and #f otherwise.
+
For example: +
+> (input-port? (current-input-port)) +#t +> (call-with-input-string "some text" output-port?) +#f +> (port? (current-output-port)) +#t + |
(read [port]) | procedure |
This procedure reads and returns the next Scheme datum from the +input-port port. The end-of-file object is returned when the +end of the stream is reached. If it is not specified, port +defaults to the current input-port. +
+For example: +
+> (call-with-input-string "some text" read) +some +> (call-with-input-string "" read) +#!eof + |
(read-all [port [reader]]) | procedure |
This procedure repeatedly calls the procedure reader with
+port as the sole argument and accumulates a list of each value
+returned up to the end-of-file object. The procedure read-all
+returns the accumulated list without the end-of-file object. If it is
+not specified, port defaults to the current input-port. If it
+is not specified, reader defaults to the procedure read.
+
For example: +
+> (call-with-input-string "3,2,1\ngo!" read-all)
+(3 ,2 ,1 go!)
+> (call-with-input-string "3,2,1\ngo!"
+ (lambda (p) (read-all p read-char)))
+(#\3 #\, #\2 #\, #\1 #\newline #\g #\o #\!)
+> (call-with-input-string "3,2,1\ngo!"
+ (lambda (p) (read-all p read-line)))
+("3,2,1" "go!")
+ |
(write obj [port]) | procedure |
This procedure writes the Scheme datum obj to the output-port +port and the value returned is unspecified. If it is not +specified, port defaults to the current output-port. +
+For example: +
+> (write (list 'compare (list 'quote '@x) 'and (list 'unquote '@x))) +(compare '@x and , @x)> + |
(newline [port]) | procedure |
This procedure writes an “object separator” to the output-port
+port and the value returned is unspecified. The separator
+ensures that the next Scheme datum written with the write
+procedure will not be confused with the latest datum that was written.
+On character-ports this is done by writing the character
+#\newline. On ports where successive objects are implicitly
+distinct (such as “vector ports”) this procedure does nothing.
+
Regardless of the class of a port p and assuming that the
+external textual representation of the object x is readable, the
+expression (begin (write x p) (newline p))
+will write to p a representation of x that can be read
+back with the procedure read. If it is not specified,
+port defaults to the current output-port.
+
For example: +
+> (begin (write 123) (newline) (write 456) (newline)) +123 +456 + |
(force-output [port [level]]) | procedure |
The procedure force-output causes the data that was written to
+the output-port port to be moved closer to its destination
+according to level, an exact integer in the range 0 to 2. If
+port is not specified, the current output-port is used. If
+level is not specified, it defaults to 0. Values of level
+above 0 are equivalent to level = 0 except for device ports as
+explained below.
+
When level is 0, the output buffers of port which are +managed in the Scheme process are drained (i.e. the output operation +that was delayed due to buffering is actually performed). In the case +of a device port the data is passed to the operating system and it +becomes its responsibility to transmit the data to the device. The +operating system may implement its own buffering approach which delays +the transmission of the data to the device. +
+When level is 1, in addition to the operations for level =
+0 and if the operating system supports the functionality, the
+operating system is requested to transmit the data to the device. On
+UNIX this corresponds to a fsync system call.
+
When level is 2, in addition to the operations for level =
+1 and if the operating system supports the functionality, the
+operating system is requested to wait until the device reports that
+the data was saved by the device (e.g. actually written to disk in the
+case of a file). This operation can take a long time on some
+operating systems. On Mac OS X this corresponds to a fcntl
+system call with operation F_FULLFSYNC.
+
For example: +
+> (define p (open-tcp-client "www.iro.umontreal.ca:80")) +> (display "GET /\n" p) +> (force-output p) +> (read-line p) +"<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\"" + |
(close-input-port port) | procedure |
(close-output-port port) | procedure |
(close-port port) | procedure |
The port argument of these procedures must be a unidirectional +or a bidirectional port. For all three procedures the value returned +is unspecified. +
+The procedure close-input-port closes the input-port side of
+port, which must not be a unidirectional output-port.
+
The procedure close-output-port closes the output-port side of
+port, which must not be a unidirectional input-port. The ouput
+buffers are drained before port is closed.
+
The procedure close-port closes all sides of the port.
+Unless port is a unidirectional input-port, the output buffers
+are drained before port is closed.
+
For example: +
+> (define p (open-tcp-client "www.iro.umontreal.ca:80")) +> (display "GET /\n" p) +> (close-output-port p) +> (read-line p) +"<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\"" + |
(input-port-timeout-set! port timeout [thunk]) | procedure |
(output-port-timeout-set! port timeout [thunk]) | procedure |
When a thread tries to perform an I/O operation on a port, the +requested operation may not be immediately possible and the thread +must wait. For example, the thread may be trying to read a line of +text from the console and the user has not typed anything yet, or the +thread may be trying to write to a network connection faster than the +network can handle. In such situations the thread normally blocks +until the operation becomes possible. +
+It is sometimes necessary to guarantee that the thread will not block
+too long. For this purpose, to each input-port and output-port is
+attached a timeout and timeout-thunk. The timeout
+indicates the point in time beyond which the thread should stop
+waiting on an input and output operation respectively. When the
+timeout is reached, the thread calls the port’s timeout-thunk. If the
+timeout-thunk returns #f the thread abandons trying to perform
+the operation (in the case of an input operation an end-of-file is
+read and in the case of an output operation an exception is raised).
+Otherwise, the thread will block again waiting for the operation to
+become possible (note that if the port’s timeout has not changed the
+thread will immediately call the timeout-thunk again).
+
The procedure input-port-timeout-set! sets the timeout of the
+input-port port to timeout and the timeout-thunk to
+thunk. The procedure output-port-timeout-set! sets the
+timeout of the output-port port to timeout and the
+timeout-thunk to thunk. If it is not specified, the thunk
+defaults to a thunk that returns #f. The timeout is
+either a time object indicating an absolute point in time, or it is a
+real number which indicates the number of seconds relative to the
+moment the procedure is called. For both procedures the value
+returned is unspecified.
+
When a port is created the timeout is set to infinity (+inf.0).
+This causes the thread to wait as long as needed for the operation to
+become possible. Setting the timeout to a point in the past
+(-inf.0) will cause the thread to attempt the I/O operation and
+never block (i.e. the timeout-thunk is called if the operation is not
+immediately possible).
+
The following example shows how to cause the REPL to terminate +when the user does not enter an expression within the next 60 seconds. +
+> (input-port-timeout-set! (repl-input-port) 60) +> +*** EOF again to exit + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
| 17.5.1 Character-port settings | ||
| 17.5.2 Character-port operations |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The following is a list of port settings that are valid for +character-ports. +
+readtable: readtable
+
+This setting determines the readtable attached to the character-port.
+To set each direction separately the keywords input-readtable:
+and output-readtable: must be used instead of
+readtable:. Readtables control the external textual
+representation of Scheme objects, that is the encoding of Scheme
+objects using characters. The behavior of the read procedure
+depends on the port’s input-readtable and the behavior of the
+procedures write, pretty-print, and related procedures
+is affected by the port’s output-readtable. The default value of this
+setting is the value bound to the parameter object
+current-readtable.
+
output-width: positive-integer
+
+This setting indicates the width of the character output-port in +number of characters. This information is used by the pretty-printer. +The default value of this setting is 80. +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(input-port-line port) | procedure |
(input-port-column port) | procedure |
(output-port-line port) | procedure |
(output-port-column port) | procedure |
The current character location of a character input-port is the
+location of the next character to read. The current character
+location of a character output-port is the location of the next
+character to write. Location is denoted by a line number (the first
+line is line 1) and a column number, that is the location on the
+current line (the first column is column 1). The procedures
+input-port-line and input-port-column return the line
+location and the column location respectively of the character
+input-port port. The procedures output-port-line and
+output-port-column return the line location and the column
+location respectively of the character output-port port.
+
For example: +
+> (call-with-output-string + '() + (lambda (p) + (display "abc\n123def" p) + (write (list (output-port-line p) (output-port-column p)) + p))) +"abc\n123def(2 7)" + |
(output-port-width port) | procedure |
This procedure returns the width, in characters, of the character +output-port port. The value returned is the port’s output-width +setting. +
+For example: +
+> (output-port-width (repl-output-port)) +80 + |
(read-char [port]) | procedure |
This procedure reads the character input-port port and returns
+the character at the current character location and advances the
+current character location to the next character, unless the
+port is already at end-of-file in which case read-char
+returns the end-of-file object. If it is not specified, port
+defaults to the current input-port.
+
For example: +
+> (call-with-input-string + "some text" + (lambda (p) + (let ((a (read-char p))) (list a (read-char p))))) +(#\s #\o) +> (call-with-input-string "" read-char) +#!eof + |
(peek-char [port]) | procedure |
This procedure returns the same result as read-char but it does
+not advance the current character location of the input-port
+port. If it is not specified, port defaults to the
+current input-port.
+
For example: +
+> (call-with-input-string + "some text" + (lambda (p) + (let ((a (peek-char p))) (list a (read-char p))))) +(#\s #\s) +> (call-with-input-string "" peek-char) +#!eof + |
(write-char char [port]) | procedure |
This procedure writes the character char to the character +output-port port and advances the current character location of +that output-port. The value returned is unspecified. If it is not +specified, port defaults to the current output-port. +
+For example: +
+> (write-char #\=) +=> + |
(read-line [port [separator [include-separator? [max-length]]]]) | procedure |
This procedure reads characters from the character input-port +port until a specific separator or the end-of-file is +encountered and returns a string containing the sequence of characters +read. If it is specified, max-length must be a nonnegative +exact integer and it places an upper limit on the number of characters +that are read. +
+The separator is included at the end of the string only
+if it was the last character read and include-separator? is not
+#f. The separator must be a character or #f (in
+which case all the characters until the end-of-file are read). If it
+is not specified, port defaults to the current input-port. If
+it is not specified, separator defaults to #\newline. If
+it is not specified, include-separator? defaults to #f.
+
For example: +
+> (define (split sep)
+ (lambda (str)
+ (call-with-input-string
+ str
+ (lambda (p)
+ (read-all p (lambda (p) (read-line p sep)))))))
+> ((split #\,) "a,b,c")
+("a" "b" "c")
+> (map (split #\,)
+ (call-with-input-string "1,2,3\n4,5"
+ (lambda (p) (read-all p read-line))))
+(("1" "2" "3") ("4" "5"))
+> (read-line (current-input-port) #\newline #f 2)1234
+"12"
+> 34
+ |
(read-substring string start end [port [need]]) | procedure |
(write-substring string start end [port]) | procedure |
These procedures support bulk character I/O. The part of the string
+string starting at index start and ending just before
+index end is used as a character buffer that will be the target
+of read-substring or the source of the write-substring.
+The read-substring also accepts a need parameter which
+must be a nonnegative fixnum. Up to end-start characters
+will be transferred. The number of characters transferred, possibly
+zero, is returned by these procedures. Fewer characters will be read
+by read-substring if an end-of-file is read, or a timeout
+occurs before all the requested characters are transferred and the
+timeout thunk returns #f (see the procedure
+input-port-timeout-set!), or need is specified and at
+least that many characters have been read (in other words the
+procedure does not block for more characters but may transfer more
+characters if they are immediately available). Fewer characters will
+be written by write-substring if a timeout occurs before all
+the requested characters are transferred and the timeout thunk returns
+#f (see the procedure output-port-timeout-set!). If it
+is not specified, port defaults to the current input-port and
+current output-port respectively.
+
For example: +
+> (define s (make-string 10 #\x)) +> (read-substring s 2 5)123456789 +3 +> 456789 +> s +"xx123xxxxx" +> (read-substring s 2 10 (current-input-port) 3)abcd +5 +> s +"xxabcd\nxxx" + |
(input-port-readtable port) | procedure |
(output-port-readtable port) | procedure |
These procedures return the readtable attached to the character-port
+port. The port parameter of input-port-readtable
+must be an input-port. The port parameter of
+output-port-readtable must be an output-port.
+
(input-port-readtable-set! port readtable) | procedure |
(output-port-readtable-set! port readtable) | procedure |
These procedures change the readtable attached to the character-port
+port to the readtable readtable. The port parameter
+of input-port-readtable-set! must be an input-port. The
+port parameter of output-port-readtable-set! must be an
+output-port. The value returned is unspecified.
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
| 17.6.1 Byte-port settings | ||
| 17.6.2 Byte-port operations |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The following is a list of port settings that are valid for +byte-ports. +
+char-encoding: encoding
+
+This setting controls the character encoding of the byte-port. For
+bidirectional byte-ports, the character encoding for input and output
+is set. To set each direction separately the keywords
+input-char-encoding: and output-char-encoding: must be
+used instead of char-encoding:. The default value of this
+setting is operating system dependent, but this can be overridden
+through the runtime options (see section Runtime options). The following
+encodings are supported:
+
ISO-8859-1ISO-8859-1 character encoding. Each character is encoded by a single byte. +Only Unicode characters with a code in the range 0 to 255 are allowed. +
+ASCIIASCII character encoding. Each character is encoded by a single byte.
+In principle only Unicode characters with a code in the range 0 to 127
+are allowed but most types of ports treat this exactly like ISO-8859-1.
+
UTF-8UTF-8 character encoding. Each character is encoded by a sequence of one +to four bytes. The minimum length UTF-8 encoding is used. If a BOM is +needed at the beginning of the stream then it must be explicitly +written. +
+UTF-16UTF-16 character encoding. Each character is encoded by one or two 16 +bit integers (2 or 4 bytes). The 16 bit integers may be encoded using +little-endian encoding or big-endian encoding. If the port is an +input-port and the first two bytes read are a BOM (“Byte Order Mark” +character with hexadecimal code FEFF) then the BOM will be discarded +and the endianness will be set accordingly, otherwise the endianness +depends on the operating system and how the Gambit runtime was +compiled. If the port is an output-port then a BOM will be output at +the beginning of the stream and the endianness depends on the +operating system and how the Gambit runtime was compiled. +
+UTF-16LEUTF-16 character encoding with little-endian endianness. It is like
+UTF-16 except the endianness is set to little-endian and there is no
+BOM processing. If a BOM is needed at the beginning of the stream
+then it must be explicitly written.
+
UTF-16BEUTF-16 character encoding with big-endian endianness. It is like
+UTF-16LE except the endianness is set to big-endian.
+
UTF / UTF-fallback-ASCII / UTF-fallback-ISO-8859-1 / UTF-fallback-UTF-16 / UTF-fallback-UTF-16LE / UTF-fallback-UTF-16BEThese encodings combine the UTF-8 and UTF-16 encodings. When one of
+these character encodings is used for an output port, characters will
+be encoded using the UTF-8 encoding. The first character, if there is
+one, is prefixed with a UTF-8 BOM (the three byte sequence EF BB BF in
+hexadecimal). When one of these character encodings is used for an
+input port, the character encoding depends on the first few bytes. If
+the first bytes of the stream are a UTF-16LE BOM (FF FE in
+hexadecimal), or a UTF-16BE BOM (FE FF in hexadecimal), or a UTF-8 BOM
+(EF BB BF in hexadecimal), then the BOM is discarded and the remaining
+bytes of the stream are decoded using the corresponding character
+encoding. If a BOM is not present, then the stream is decoded using
+the fallback encoding specified. The encoding UTF is a synonym
+for UTF-fallback-UTF-8. Note that the UTF character
+encoding for input will correctly handle streams produced using the
+encodings UTF, UTF-8, UTF-16, ASCII, and
+if an explicit BOM is output, the encodings UTF-16LE, and
+UTF-16BE.
+
UCS-2UCS-2 character encoding. Each character is encoded by a 16 bit +integer (2 bytes). The 16 bit integers may be encoded using +little-endian encoding or big-endian encoding. If the port is an +input-port and the first two bytes read are a BOM (“Byte Order Mark” +character with hexadecimal code FEFF) then the BOM will be discarded +and the endianness will be set accordingly, otherwise the endianness +depends on the operating system and how the Gambit runtime was +compiled. If the port is an output-port then a BOM will be output at +the beginning of the stream and the endianness depends on the +operating system and how the Gambit runtime was compiled. +
+UCS-2LEUCS-2 character encoding with little-endian endianness. It is like
+UCS-2 except the endianness is set to little-endian and there is no
+BOM processing. If a BOM is needed at the beginning of the stream
+then it must be explicitly written.
+
UCS-2BEUCS-2 character encoding with big-endian endianness. It is like
+UCS-2LE except the endianness is set to big-endian.
+
UCS-4UCS-4 character encoding. Each character is encoded by a 32 integer +(4 bytes). The 32 bit integers may be encoded using little-endian +encoding or big-endian encoding. If the port is an input-port and the +first four bytes read are a BOM (“Byte Order Mark” character with +hexadecimal code 0000FEFF) then the BOM will be discarded and the +endianness will be set accordingly, otherwise the endianness depends +on the operating system and how the Gambit runtime was compiled. If +the port is an output-port then a BOM will be output at the beginning +of the stream and the endianness depends on the operating system and +how the Gambit runtime was compiled. +
+UCS-4LEUCS-4 character encoding with little-endian endianness. It is like
+UCS-4 except the endianness is set to little-endian and there is no
+BOM processing. If a BOM is needed at the beginning of the stream
+then it must be explicitly written.
+
UCS-4BEUCS-4 character encoding with big-endian endianness. It is like
+UCS-4LE except the endianness is set to big-endian.
+
char-encoding-errors: ( #f | #t )
+
+This setting controls whether illegal character encodings are silently
+replaced with the Unicode character #xfffd (replacement character) or
+raise an error. To set each direction separately the keywords
+input-char-encoding-errors: and
+output-char-encoding-errors: must be used instead of
+char-encoding-errors:. The default value of this setting is
+#t.
+
eol-encoding: encoding
+
+This setting controls the end-of-line encoding of the byte-port. To
+set each direction separately the keywords input-eol-encoding:
+and output-eol-encoding: must be used instead of
+eol-encoding:. The default value of this setting is operating
+system dependent, but this can be overridden through the runtime
+options (see section Runtime options). Note that for output-ports the
+end-of-line encoding is applied before the character encoding, and for
+input-ports it is applied after. The following encodings are
+supported:
+
lfFor an output-port, writing a #\newline character outputs a
+#\linefeed character to the stream (Unicode character code 10).
+For an input-port, a #\newline character is read when a
+#\linefeed character is encountered on the stream. Note that
+#\linefeed and #\newline are two names for the same
+character, so this end-of-line encoding is actually the identity
+function. Text files created by UNIX applications typically use this
+end-of-line encoding.
+
crFor an output-port, writing a #\newline character outputs a
+#\return character to the stream (Unicode character code 13).
+For an input-port, a #\newline character is read when a
+#\linefeed character or a #\return character is
+encountered on the stream. Text files created by Classic Mac OS
+applications typically use this end-of-line encoding.
+
cr-lfFor an output-port, writing a #\newline character outputs to
+the stream a #\return character followed by a #\linefeed
+character. For an input-port, a #\newline character is read
+when a #\linefeed character or a #\return character is
+encountered on the stream. Moreover, if this character is immediately
+followed by the opposite character (#\linefeed followed by
+#\return or #\return followed by #\linefeed) then
+the second character is ignored. In other words, all four possible
+end-of-line encodings are read as a single #\newline character.
+Text files created by DOS and Microsoft Windows applications typically
+use this end-of-line encoding.
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(read-u8 [port]) | procedure |
This procedure reads the byte input-port port and returns the
+byte at the current byte location and advances the current byte
+location to the next byte, unless the port is already at
+end-of-file in which case read-u8 returns the end-of-file
+object. If it is not specified, port defaults to the current
+input-port.
+
This procedure must be called when the port’s input character buffer +is empty otherwise the character-stream and byte-stream may be out of +sync due to buffering. The input character buffer is used for bulk +decoding of encoded characters (i.e. to translate the byte-stream into +a character-stream). The input character buffer is initially empty. +It is only when characters are read that it is filled with characters +obtained by decoding the byte-stream. +
+One way to ensure that the port’s input character buffer is empty is
+to call read-u8 strictly before any use of the port in a character
+input operation (i.e. a call to the procedures read,
+read-char, peek-char, etc). Alternatively
+input-port-characters-buffered can be used to get the number of
+characters in the port’s input character buffer, and to empty the
+buffer with calls to read-char or read-substring.
+
For example: +
+> (call-with-input-u8vector + '#u8(11 22 33 44) + (lambda (p) + (let ((a (read-u8 p))) (list a (read-u8 p))))) +(11 22) +> (call-with-input-u8vector '#u8() read-u8) +#!eof + |
(write-u8 n [port]) | procedure |
This procedure writes the byte n to the byte output-port +port and advances the current byte location of that output-port. +The value returned is unspecified. If it is not specified, port +defaults to the current output-port. +
+For example: +
+> (call-with-output-u8vector '() (lambda (p) (write-u8 33 p))) +#u8(33) + |
(read-subu8vector u8vector start end [port [need]]) | procedure |
(write-subu8vector u8vector start end [port]) | procedure |
These procedures support bulk byte I/O. The part of the u8vector
+u8vector starting at index start and ending just before
+index end is used as a byte buffer that will be the target of
+read-subu8vector or the source of the write-subu8vector.
+The read-subu8vector also accepts a need parameter which
+must be a nonnegative fixnum. Up to end-start bytes will
+be transferred. The number of bytes transferred, possibly zero, is
+returned by these procedures. Fewer bytes will be read by
+read-subu8vector if an end-of-file is read, or a timeout occurs
+before all the requested bytes are transferred and the timeout thunk
+returns #f (see the procedure input-port-timeout-set!),
+or need is specified and at least that many bytes have been read
+(in other words the procedure does not block for more bytes but may
+transfer more bytes if they are immediately available). Fewer bytes
+will be written by write-subu8vector if a timeout occurs before
+all the requested bytes are transferred and the timeout thunk returns
+#f (see the procedure output-port-timeout-set!). If it
+is not specified, port defaults to the current input-port and
+current output-port respectively.
+
The procedure read-subu8vector must be called before any use of
+the port in a character input operation (i.e. a call to the procedures
+read, read-char, peek-char, etc) because
+otherwise the character-stream and byte-stream may be out of sync due
+to the port buffering.
+
For example: +
+> (define v (make-u8vector 10)) +> (read-subu8vector v 2 5)123456789 +3 +> 456789 +> v +#u8(0 0 49 50 51 0 0 0 0 0) +> (read-subu8vector v 2 10 (current-input-port) 3)abcd +5 +> v +#u8(0 0 97 98 99 100 10 0 0 0) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
| 17.7.1 Filesystem devices | ||
| 17.7.2 Process devices | ||
| 17.7.3 Network devices |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(open-file path-or-settings) | procedure |
(open-input-file path-or-settings) | procedure |
(open-output-file path-or-settings) | procedure |
(call-with-input-file path-or-settings proc) | procedure |
(call-with-output-file path-or-settings proc) | procedure |
(with-input-from-file path-or-settings thunk) | procedure |
(with-output-to-file path-or-settings thunk) | procedure |
All of these procedures create a port to interface to a byte-stream
+device (such as a file, console, serial port, named pipe, etc) whose
+name is given by a path of the filesystem. The direction:
+setting will default to the value input for the procedures
+open-input-file, call-with-input-file and
+with-input-from-file, to the value output for the
+procedures open-output-file, call-with-output-file and
+with-output-to-file, and to the value input-output for
+the procedure open-file.
+
The procedures open-file, open-input-file and
+open-output-file return the port that is created. The
+procedures call-with-input-file and
+call-with-output-file call the procedure proc with the
+port as single argument, and then return the value(s) of this call
+after closing the port. The procedures with-input-from-file
+and with-output-to-file dynamically bind the current input-port
+and current output-port respectively to the port created for the
+duration of a call to the procedure thunk with no argument. The
+value(s) of the call to thunk are returned after closing the
+port.
+
The first argument of these procedures is either a string denoting a
+filesystem path or a list of port settings which must contain a
+path: setting. Here are the settings allowed in addition to
+the generic settings of byte-ports:
+
path: string
+
+This setting indicates the location of the file in the filesystem. +There is no default value for this setting. +
+append: ( #f | #t )
+
+This setting controls whether output will be added to the end of the
+file. This is useful for writing to log files that might be open by
+more than one process. The default value of this setting is
+#f.
+
create: ( #f | #t | maybe )
+
+This setting controls whether the file will be created when it is
+opened. A setting of #f requires that the file exist
+(otherwise an exception is raised). A setting of #t requires
+that the file does not exist (otherwise an exception is raised). A
+setting of maybe will create the file if it does not exist.
+The default value of this setting is maybe for output-ports and
+#f for input-ports and bidirectional ports.
+
permissions: 12-bit-exact-integer
+
+This setting controls the UNIX permissions that will be attached to
+the file if it is created. The default value of this setting is
+#o666.
+
truncate: ( #f | #t )
+
+This setting controls whether the file will be truncated when it is
+opened. For input-ports, the default value of this setting is
+#f. For output-ports, the default value of this setting is
+#t when the append: setting is #f, and #f
+otherwise.
+
For example: +
+> (with-output-to-file + (list path: "nofile" + create: #f) + (lambda () + (display "hello world!\n"))) +*** ERROR IN (console)@1.1 -- No such file or directory +(with-output-to-file '(path: "nofile" create: #f) '#<procedure #2>) + |
(input-port-byte-position port [position [whence]]) | procedure |
(output-port-byte-position port [position [whence]]) | procedure |
When called with a single argument these procedures return the byte +position where the next I/O operation would take place in the file +attached to the given port (relative to the beginning of the +file). When called with two or three arguments, the byte position for +subsequent I/O operations on the given port is changed to +position, which must be an exact integer. When whence is +omitted or is 0, the position is relative to the beginning of +the file. When whence is 1, the position is relative to +the current byte position of the file. When whence is 2, the +position is relative to the end of the file. The return value +is the new byte position. On most operating systems the byte position +for reading and writing of a given bidirectional port are the same. +
+When input-port-byte-position is called to change the byte
+position of an input-port, all input buffers will be flushed so that
+the next byte read will be the one at the given position.
+
When output-port-byte-position is called to change the byte
+position of an output-port, there is an implicit call to
+force-output before the position is changed.
+
For example: +
+> (define p ; p is an input-output-port
+ (open-file '(path: "test" char-encoding: ISO-8859-1 create: maybe)))
+> (list (input-port-byte-position p) (output-port-byte-position p))
+(0 0)
+> (display "abcdefghij\n" p)
+> (list (input-port-byte-position p) (output-port-byte-position p))
+(0 0)
+> (force-output p)
+> (list (input-port-byte-position p) (output-port-byte-position p))
+(11 11)
+> (input-port-byte-position p 2)
+2
+> (list (input-port-byte-position p) (output-port-byte-position p))
+(2 2)
+> (peek-char p)
+#\c
+> (list (input-port-byte-position p) (output-port-byte-position p))
+(11 11)
+> (output-port-byte-position p -7 2)
+4
+> (list (input-port-byte-position p) (output-port-byte-position p))
+(4 4)
+> (write-char #\! p)
+> (list (input-port-byte-position p) (output-port-byte-position p))
+(4 4)
+> (force-output p)
+> (list (input-port-byte-position p) (output-port-byte-position p))
+(5 5)
+> (input-port-byte-position p 1)
+1
+> (read p)
+bcd!fghij
+ |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(open-process path-or-settings) | procedure |
(open-input-process path-or-settings) | procedure |
(open-output-process path-or-settings) | procedure |
(call-with-input-process path-or-settings proc) | procedure |
(call-with-output-process path-or-settings proc) | procedure |
(with-input-from-process path-or-settings thunk) | procedure |
(with-output-to-process path-or-settings thunk) | procedure |
All of these procedures start a new operating system process and
+create a bidirectional port which allows communication with that
+process on its standard input and standard output. The
+direction: setting will default to the value input for
+the procedures open-input-process,
+call-with-input-process and with-input-from-process, to
+the value output for the procedures open-output-process,
+call-with-output-process and with-output-to-process, and
+to the value input-output for the procedure
+open-process. If the direction: setting is
+input, the output-port side is closed. If the
+direction: setting is output, the input-port side is
+closed.
+
The procedures open-process, open-input-process and
+open-output-process return the port that is created. The
+procedures call-with-input-process and
+call-with-output-process call the procedure proc with the
+port as single argument, and then return the value(s) of this call
+after closing the port and waiting for the process to terminate. The
+procedures with-input-from-process and
+with-output-to-process dynamically bind the current input-port
+and current output-port respectively to the port created for the
+duration of a call to the procedure thunk with no argument. The
+value(s) of the call to thunk are returned after closing the
+port and waiting for the process to terminate.
+
The first argument of this procedure is either a string denoting a
+filesystem path of an executable program or a list of port settings
+which must contain a path: setting. Here are the settings
+allowed in addition to the generic settings of byte-ports:
+
path: string
+
+This setting indicates the location of the executable program in the +filesystem. There is no default value for this setting. +
+arguments: list-of-strings
+
+This setting indicates the string arguments that are passed to the +program. The default value of this setting is the empty list (i.e. no +arguments). +
+environment: list-of-strings
+
+This setting indicates the set of environment variable bindings that
+the process receives. Each element of the list is a string of the
+form “VAR=VALUE”, where VAR is the
+name of the variable and VALUE is its binding. When
+list-of-strings is #f, the process inherits the
+environment variable bindings of the Scheme program. The default
+value of this setting is #f.
+
directory: dir
+
+This setting indicates the current working directory of the process.
+When dir is #f, the process uses the value of
+(current-directory). The default value of this setting is
+#f.
+
stdin-redirection: ( #f | #t )
+
+This setting indicates how the standard input of the process is
+redirected. A setting of #t will redirect the standard input
+from the process-port (i.e. what is written to the process-port will
+be available on the standard input). A setting of #f will
+leave the standard input as-is, which typically results in input
+coming from the console. The default value of this setting is
+#t.
+
stdout-redirection: ( #f | #t )
+
+This setting indicates how the standard output of the process is
+redirected. A setting of #t will redirect the standard output
+to the process-port (i.e. all output to standard output can be read
+from the process-port). A setting of #f will leave the
+standard output as-is, which typically results in the output going to
+the console. The default value of this setting is #t.
+
stderr-redirection: ( #f | #t )
+
+This setting indicates how the standard error of the process is
+redirected. A setting of #t will redirect the standard error
+to the process-port (i.e. all output to standard error can be read
+from the process-port). A setting of #f will leave the
+standard error as-is, which typically results in error messages being
+output to the console. The default value of this setting is
+#f.
+
pseudo-terminal: ( #f | #t )
+
+This setting applies to UNIX. It indicates what type of device will
+be bound to the process’ standard input and standard output. A
+setting of #t will use a pseudo-terminal device (this is a
+device that behaves like a tty device even though there is no real
+terminal or user directly involved). A setting of #f will use
+a pair of pipes. The difference is important for programs which
+behave differently when they are used interactively, for example
+shells. The default value of this setting is #f.
+
show-console: ( #f | #t )
+
+This setting applies to Microsoft Windows. It controls whether the
+process’ console window will be hidden or visible. The default value
+of this setting is #t (i.e. show the console window).
+
For example: +
+> (with-input-from-process "date" read-line)
+"Sun Jun 14 15:06:41 EDT 2009"
+> (define p (open-process (list path: "ls"
+ arguments: '("../examples"))))
+> (read-line p)
+"README"
+> (read-line p)
+"Xlib-simple"
+> (close-port p)
+> (define p (open-process "/usr/bin/dc"))
+> (display "2 100 ^ p\n" p)
+> (force-output p)
+> (read-line p)
+"1267650600228229401496703205376"
+ |
(process-pid process-port) | procedure |
This procedure returns the PID (Process Identifier) of the process of +process-port. The PID is a small exact integer. +
+For example: +
+> (let ((p (open-process "sort"))) + (process-pid p)) +318 + |
(process-status process-port [timeout [timeout-val]]) | procedure |
This procedure causes the current thread to wait until the process of +process-port terminates (normally or not) or until the timeout +is reached if timeout is supplied. If the timeout is reached, +process-status returns timeout-val if it is supplied, +otherwise an unterminated-process-exception object is raised. The +procedure returns the process exit status as encoded by the operating +system. Typically, if the process exited normally the return value is +the process exit status multiplied by 256. +
+For example: +
+> (let ((p (open-process "sort"))) + (for-each (lambda (x) (pretty-print x p)) + '(22 11 33)) + (close-output-port p) + (let ((r (read-all p))) + (close-input-port p) + (list (process-status p) r))) +(0 (11 22 33)) + |
(unterminated-process-exception? obj) | procedure |
(unterminated-process-exception-procedure exc) | procedure |
(unterminated-process-exception-arguments exc) | procedure |
Unterminated-process-exception objects are raised when a call to the
+process-status procedure reaches its timeout before the target
+process terminates and a timeout-value parameter is not specified.
+The parameter exc must be an unterminated-process-exception
+object.
+
The procedure unterminated-process-exception? returns
+#t when obj is an unterminated-process-exception
+object and #f otherwise.
+
The procedure unterminated-process-exception-procedure
+returns the procedure that raised exc.
+
The procedure unterminated-process-exception-arguments
+returns the list of arguments of the procedure that raised exc.
+
For example: +
+> (define (handler exc) + (if (unterminated-process-exception? exc) + (list (unterminated-process-exception-procedure exc) + (unterminated-process-exception-arguments exc)) + 'not-unterminated-process-exception)) +> (with-exception-catcher + handler + (lambda () + (let ((p (open-process "sort"))) + (process-status p 1)))) +(#<procedure #2 process-status> (#<input-output-port #3 (process "sort")>)) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(open-tcp-client port-number-or-address-or-settings) | procedure |
This procedure opens a network connection to a socket server and
+returns a tcp-client-port (a subtype of device-port) that represents
+this connection and allows communication with that server. The
+default value of the direction: setting is input-output,
+i.e. the Scheme program can send information to the server and receive
+information from the server. The sending direction can be
+“shutdown” using the close-output-port procedure and the
+receiving direction can be “shutdown” using the
+close-input-port procedure. The close-port procedure
+closes both directions of the connection.
+
The parameter of this procedure is an IP port number (16-bit nonnegative
+exact integer), a string of the form "HOST:PORT" or
+a list of port settings. When the parameter is the number PORT
+it is handled as if it was the setting port-number: PORT.
+When the parameter is the string "HOST:PORT" it is
+handled as if it was the setting server-address:
+"HOST:PORT".
+
Here are the settings allowed in addition to the generic settings of +byte-ports: +
+server-address: string-or-ip-address
+
+This setting indicates the internet address of the server, and
+possibly the IP port number. When this parameter is not specified or
+is "", the connection requests are sent to the loopback
+interface (with IP address 127.0.0.1). The parameter can be a string
+denoting a host name, which will be translated to an IP address by the
+host-info procedure, or a 4 element u8vector which contains the
+32-bit IPv4 address or an 8 element u16vector which contains the
+128-bit IPv6 address. A string of the form
+"HOST:PORT" is handled as if it was the combination
+of settings server-address: "HOST"
+port-number: PORT.
+
port-number: 16-bit-exact-integer
+
+This setting indicates the IP port number of the server to connect +to (e.g. 80 for the standard HTTP server, 23 for the standard telnet +server). There is no default value for this setting. +
+keep-alive: ( #f | #t )
+
+This setting controls the use of the “keep alive” option on the
+connection. The “keep alive” option will periodically send control
+packets on otherwise idle network connections to ensure that the
+server host is active and reachable. The default value of this
+setting is #f.
+
coalesce: ( #f | #t )
+
+This setting controls the use of TCP’s “Nagle algorithm” which
+reduces the number of small packets by delaying their transmission and
+coalescing them into larger packets. A setting of #t will
+coalesce small packets into larger ones. A setting of #f will
+transmit packets as soon as possible. The default value of this
+setting is #t. Note that this setting does not affect the
+buffering of the port.
+
Below is an example of the client-side code that opens a connection to
+an HTTP server on port 8080 of the loopback interface (with IP address
+127.0.0.1). For the server-side code see the example for the
+procedure open-tcp-server.
+
> (define p (open-tcp-client (list port-number: 8080 + eol-encoding: 'cr-lf))) +> p +#<input-output-port #2 (tcp-client #u8(127 0 0 1) 8080)> +> (display "GET /\n" p) +> (force-output p) +> (read-line p) +"<HTML>" + |
(open-tcp-server port-number-or-address-or-settings) | procedure |
This procedure sets up a socket to accept network connection requests
+from clients and returns a tcp-server-port from which network
+connections to clients are obtained. Tcp-server-ports are a direct
+subtype of object-ports (i.e. they are not character-ports) and are
+input-ports. Reading from a tcp-server-port with the read
+procedure will block until a network connection request is received
+from a client. The read procedure will then return a
+tcp-client-port (a subtype of device-port) that represents this
+connection and allows communication with that client. Closing a
+tcp-server-port with either the close-input-port or
+close-port procedures will cause the network subsystem to stop
+accepting connections on that socket.
+
The parameter of this procedure is an IP port number (16-bit nonnegative
+exact integer), a string of the form "INTF:PORT" or
+a list of port settings which must contain a port-number:
+setting. When the parameter is the number PORT it is handled as
+if it was the setting port-number: PORT. When the
+parameter is the string "INTF:PORT" it is handled
+as if it was the setting server-address:
+"INTF:PORT".
+
Below is a list of the settings allowed in addition to the settings
+keep-alive: and coalesce: allowed by the
+open-tcp-client procedure and the generic settings of
+byte-ports. The settings which are not listed below apply to the
+tcp-client-port that is returned by read when a connection is
+accepted and have the same meaning as if they were used in a call to
+the open-tcp-client procedure.
+
server-address: string-or-ip-address
+
+This setting indicates the internet address of the network interface
+on which connections requests are accepted, and possibly the IP port
+number. When this parameter is not specified or is "", the
+connection requests are accepted only on the loopback interface (with
+IP address 127.0.0.1). When this parameter is "*", the
+connection requests are accepted on all network interfaces
+(i.e. address INADDR_ANY). The parameter can be a string denoting a
+host name, which will be translated to an IP address by the
+host-info procedure, or a 4 element u8vector which contains the
+32-bit IPv4 address or an 8 element u16vector which contains the
+128-bit IPv6 address. A string of the form
+"INTF:PORT" is handled as if it was the combination
+of settings server-address: "INTF"
+port-number: PORT.
+
port-number: 16-bit-exact-integer
+
+This setting indicates the IP port number assigned to the socket which
+accepts connection requests from clients. So called “well-known
+ports”, which are reserved for standard services, have a port number
+below 1024 and can only be assigned to a socket by a process with
+superuser priviledges (e.g. 80 for the HTTP service, 23 for the telnet
+service). No special priviledges are needed to assign higher
+port numbers to a socket. The special value 0 requests that a
+currently unused port number be assigned to the socket (the port
+number assigned can be retrieved using the procedure
+tcp-server-socket-info). There is no default value for this
+setting.
+
backlog: positive-exact-integer
+
+This setting indicates the maximum number of connection requests that
+can be waiting to be accepted by a call to read (technically it
+is the value passed as the second argument of the UNIX listen()
+function). The default value of this setting is 128.
+
reuse-address: ( #f | #t )
+
+This setting controls whether it is possible to assign a port number
+that is currently active. Note that when a server process terminates,
+the socket it was using to accept connection requests does not become
+inactive immediately. Instead it remains active for a few minutes to
+ensure clean termination of the connections. A setting of #f
+will cause an exception to be raised in that case. A setting of
+#t will allow a port number to be used even if it is active.
+The default value of this setting is #t.
+
Below is an example of the server-side code that accepts connections
+on port 8080 of any network interface. For the client-side code see
+the example for the procedure open-tcp-client.
+
> (define s (open-tcp-server (list server-address: "*"
+ port-number: 8080
+ eol-encoding: 'cr-lf)))
+> (define p (read s)) ; blocks until client connects
+> p
+#<input-output-port #2 (tcp-client 8080)>
+> (read-line p)
+"GET /"
+> (display "<HTML>\n" p)
+> (force-output p)
+ |
(tcp-service-register! port-number-or-address-or-settings thunk [thread-group]) | procedure |
(tcp-service-unregister! port-number-or-address-or-settings) | procedure |
The procedure tcp-service-register! sets up a socket to accept
+network connection requests from clients and creates a “service”
+thread which processes the incoming connections. The parameter
+port-number-or-address-or-settings has the same meaning as for
+the procedure open-tcp-server.
+
For each connection established the service thread creates a +“handler” thread which executes a call to the procedure thunk +with no argument. The handler thread’s current input-port and current +output-port are both set to the tcp-client-port created for the +connection. There is no need for the thunk to close the +tcp-client-port, as this is done by the handler thread when the +thunk returns normally. +
+The procedure tcp-service-unregister! terminates the service
+thread which was registered by tcp-service-register! with the
+same network interface and port number (if a service thread is still
+registered). The procedure tcp-service-register! implicitly
+calls tcp-service-unregister! before registering the new
+service thread.
+
> (tcp-service-register! + 8000 + (lambda () (display "hello\n"))) +> (define p (open-tcp-client 8000)) +> (read-line p) +"hello" +> (tcp-service-unregister! 8000) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(open-directory path-or-settings) | procedure |
This procedure opens a directory of the filesystem for reading its
+entries and returns a directory-port from which the entries can be
+enumerated. Directory-ports are a direct subtype of object-ports
+(i.e. they are not character-ports) and are input-ports. Reading from
+a directory-port with the read procedure returns the next file
+name in the directory as a string. The end-of-file object is returned
+when all the file names have been enumerated. Another way to get the
+list of all files in a directory is the directory-files
+procedure which returns a list of the files in the directory. The
+advantage of using directory-ports is that it allows iterating over
+the files in a directory in constant space, which is interesting when
+the number of files in the directory is not known in advance and may
+be large. Note that the order in which the names are returned is
+operating-system dependent.
+
The parameter of this procedure is either a string denoting a
+filesystem path to a directory or a list of port settings which must
+contain a path: setting. Here are the settings allowed in
+addition to the generic settings of object-ports:
+
path: string
+
+This setting indicates the location of the directory in the filesystem. +There is no default value for this setting. +
+ignore-hidden: ( #f | #t | dot-and-dot-dot )
+
+This setting controls whether hidden-files will be returned. Under
+UNIX and Mac OS X hidden-files are those that start with a period
+(such as ., .., and .profile). Under Microsoft
+Windows hidden files are the . and .. entries and the
+files whose “hidden file” attribute is set. A setting of #f
+will enumerate all the files. A setting of #t will only
+enumerate the files that are not hidden. A setting of
+dot-and-dot-dot will enumerate all the files except for the
+. and .. hidden files. The default value of this
+setting is #t.
+
For example: +
+> (let ((p (open-directory (list path: "../examples"
+ ignore-hidden: #f))))
+ (let loop ()
+ (let ((fn (read p)))
+ (if (string? fn)
+ (begin
+ (pp (path-expand fn))
+ (loop)))))
+ (close-input-port p))
+"/u/feeley/examples/."
+"/u/feeley/examples/.."
+"/u/feeley/examples/complex"
+"/u/feeley/examples/README"
+"/u/feeley/examples/simple"
+> (define x (open-directory "../examples"))
+> (read-all x)
+("complex" "README" "simple")
+ |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(open-vector [vector-or-settings]) | procedure |
(open-input-vector [vector-or-settings]) | procedure |
(open-output-vector [vector-or-settings]) | procedure |
(call-with-input-vector vector-or-settings proc) | procedure |
(call-with-output-vector vector-or-settings proc) | procedure |
(with-input-from-vector vector-or-settings thunk) | procedure |
(with-output-to-vector vector-or-settings thunk) | procedure |
Vector-ports represent streams of Scheme objects. They are a direct
+subtype of object-ports (i.e. they are not character-ports). All of
+these procedures create vector-ports that are either unidirectional or
+bidirectional. The direction: setting will default to the
+value input for the procedures open-input-vector,
+call-with-input-vector and with-input-from-vector, to
+the value output for the procedures open-output-vector,
+call-with-output-vector and with-output-to-vector, and
+to the value input-output for the procedure open-vector.
+Bidirectional vector-ports behave like FIFOs: data written to the port
+is added to the end of the stream that is read. It is only when a
+bidirectional vector-port’s output-side is closed with a call to the
+close-output-port procedure that the stream’s end is known
+(when the stream’s end is reached, reading the port returns the
+end-of-file object).
+
The procedures open-vector, open-input-vector and
+open-output-vector return the port that is created. The
+procedures call-with-input-vector and
+call-with-output-vector create a vector port, call the
+procedure proc with the port as single argument and then close
+the port. The procedures with-input-from-vector and
+with-output-to-vector create a vector port, dynamically bind
+the current input-port and current output-port respectively to the
+port created for the duration of a call to the procedure thunk
+with no argument, and then close the port. The procedures
+call-with-input-vector and with-input-from-vector return
+the value returned by the procedures proc and thunk
+respectively. The procedures call-with-output-vector and
+with-output-to-vector return the vector accumulated in the port
+(see get-output-vector).
+
The first parameter of these procedures is either a vector of the
+elements used to initialize the stream or a list of port settings. If
+it is not specified, the parameter of the open-vector,
+open-input-vector, and open-output-vector procedures
+defaults to an empty list of port settings. Here are the settings
+allowed in addition to the generic settings of object-ports:
+
init: vector
+
+This setting indicates the initial content of the stream. The default +value of this setting is an empty vector. +
+permanent-close: ( #f | #t )
+
+This setting controls whether a call to the procedures
+close-output-port will close the output-side of a bidirectional
+vector-port permanently or not. A permanently closed bidirectional
+vector-port whose end-of-file has been reached on the input-side will
+return the end-of-file object for all subsequent calls to the
+read procedure. A non-permanently closed bidirectional
+vector-port will return to its opened state when its end-of-file is
+read. The default value of this setting is #t.
+
For example: +
+> (define p (open-vector)) +> (write 1 p) +> (write 2 p) +> (write 3 p) +> (force-output p) +> (read p) +1 +> (read p) +2 +> (close-output-port p) +> (read p) +3 +> (read p) +#!eof +> (with-output-to-vector '() (lambda () (write 1) (write 2))) +#(1 2) + |
(open-vector-pipe [vector-or-settings1 [vector-or-settings2]]) | procedure |
The procedure open-vector-pipe creates two vector-ports and
+returns these two ports. The two ports are interrelated as follows:
+the first port’s output-side is connected to the second port’s
+input-side and the first port’s input-side is connected to the second
+port’s output-side. The value vector-or-settings1 is used to
+setup the first vector-port and vector-or-settings2 is used to
+setup the second vector-port. The same settings as for
+open-vector are allowed. The default direction: setting
+is input-output (i.e. a bidirectional port is created). If it
+is not specified vector-or-settings1 defaults to the empty list.
+If it is not specified vector-or-settings2 defaults to
+vector-or-settings1 but with the init: setting set to the
+empty vector and with the input and output settings exchanged (e.g. if
+the first port is an input-port then the second port is an
+output-port, if the first port’s input-side is non-buffered then the
+second port’s output-side is non-buffered).
+
For example: +
+> (define (server op)
+ (receive (c s) (open-vector-pipe) ; client-side and server-side ports
+ (thread-start!
+ (make-thread
+ (lambda ()
+ (let loop ()
+ (let ((request (read s)))
+ (if (not (eof-object? request))
+ (begin
+ (write (op request) s)
+ (newline s)
+ (force-output s)
+ (loop))))))))
+ c))
+> (define a (server (lambda (x) (expt 2 x))))
+> (define b (server (lambda (x) (expt 10 x))))
+> (write 100 a)
+> (write 30 b)
+> (read a)
+1267650600228229401496703205376
+> (read b)
+1000000000000000000000000000000
+ |
(get-output-vector vector-port) | procedure |
The procedure get-output-vector takes an output vector-port or
+a bidirectional vector-port as parameter and removes all the objects
+currently on the output-side, returning them in a vector. The port
+remains open and subsequent output to the port and calls to the
+procedure get-output-vector are possible.
+
For example: +
+> (define p (open-vector '#(1 2 3))) +> (write 4 p) +> (get-output-vector p) +#(1 2 3 4) +> (write 5 p) +> (write 6 p) +> (get-output-vector p) +#(5 6) + |
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+ |
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+ |
+ |
+ |
+ |
+ |
+
(open-string [string-or-settings]) | procedure |
(open-input-string [string-or-settings]) | procedure |
(open-output-string [string-or-settings]) | procedure |
(call-with-input-string string-or-settings proc) | procedure |
(call-with-output-string string-or-settings proc) | procedure |
(with-input-from-string string-or-settings thunk) | procedure |
(with-output-to-string string-or-settings thunk) | procedure |
(open-string-pipe [string-or-settings1 [string-or-settings2]]) | procedure |
(get-output-string string-port) | procedure |
String-ports represent streams of characters. They are a direct +subtype of character-ports. These procedures are the string-port +analog of the procedures specified in the vector-ports section. Note +that these procedures are a superset of the procedures specified in +the “Basic String Ports SRFI” (SRFI 6). +
+For example: +
+> (define p (open-string)) +> (write 1 p) +> (write 2 p) +> (write 3 p) +> (force-output p) +> (read-char p) +#\1 +> (read-char p) +#\2 +> (close-output-port p) +> (read-char p) +#\3 +> (read-char p) +#!eof +> (with-output-to-string '() (lambda () (write 1) (write 2))) +"12" + |
(object->string obj [n]) | procedure |
This procedure converts the object obj to its external +representation and returns it in a string. The parameter n +specifies the maximal width of the resulting string. If the external +representation is wider than n, the resulting string will be +truncated to n characters and the last 3 characters will be set +to periods. Note that the current readtable is used. +
+For example: +
+> (object->string (expt 2 100)) +"1267650600228229401496703205376" +> (object->string (expt 2 100) 30) +"126765060022822940149670320..." +> (object->string (cons car cdr)) +"(#<procedure #2 car> . #<procedure #3 cdr>)" + |
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+ |
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+ |
+ |
+ |
+ |
+ |
+
(open-u8vector [u8vector-or-settings]) | procedure |
(open-input-u8vector [u8vector-or-settings]) | procedure |
(open-output-u8vector [u8vector-or-settings]) | procedure |
(call-with-input-u8vector u8vector-or-settings proc) | procedure |
(call-with-output-u8vector u8vector-or-settings proc) | procedure |
(with-input-from-u8vector u8vector-or-settings thunk) | procedure |
(with-output-to-u8vector u8vector-or-settings thunk) | procedure |
(open-u8vector-pipe [u8vector-or-settings1 [u8vector-or-settings2]]) | procedure |
(get-output-u8vector u8vector-port) | procedure |
U8vector-ports represent streams of bytes. They are a direct subtype +of byte-ports. These procedures are the u8vector-port analog of the +procedures specified in the vector-ports section. +
+For example: +
+> (define p (open-u8vector)) +> (write 1 p) +> (write 2 p) +> (write 3 p) +> (force-output p) +> (read-u8 p) +49 +> (read-u8 p) +50 +> (close-output-port p) +> (read-u8 p) +51 +> (read-u8 p) +#!eof +> (with-output-to-u8vector '() (lambda () (write 1) (write 2))) +#u8(49 50) + |
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+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
(current-input-port [new-value]) | procedure |
(current-output-port [new-value]) | procedure |
(current-error-port [new-value]) | procedure |
(current-readtable [new-value]) | procedure |
These procedures are parameter objects which represent respectively: +the current input-port, the current output-port, the current +error-port, and the current readtable. +
+ + + (print [port: port] obj…) | procedure |
(println [port: port] obj…) | procedure |
The print procedure writes a representation of each obj,
+from left to right, to port. When a compound object is
+encountered (pair, list, vector, box) the elements of that object are
+recursively written without the surrounding tokens (parentheses,
+spaces, dots, etc). Strings, symbols, keywords and characters are
+written like the display procedure. If there are more than one
+obj, the first obj must not be a keyword object. If it is
+not specified, port defaults to the current output-port. The
+procedure print returns an unspecified value.
+
The println procedure does the same thing as the print
+procedure and then writes an end of line to port.
+
For example: +
+> (println "2*2 is " (* 2 2) " and 2+2 is " (+ 2 2)) +2*2 is 4 and 2+2 is 4 +> (define x (list "<i>" (list "<tt>" 123 "</tt>") "</i>")) +> (println x) +<i><tt>123</tt></i> +> (define p (open-output-string)) +> (print port: p 1 #\2 "345") +> (get-output-string p) +"12345" + |
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+ |
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+ |
+ |
+ |
+ |
+ |
+
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+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
Readtables control the external textual representation of Scheme
+objects, that is the encoding of Scheme objects using characters.
+Readtables affect the behavior of the reader (i.e. the read
+procedure and the parser used by the load procedure and the
+interpreter and compiler) and the printer (i.e. the procedures
+write, display, print, println,
+pretty-print, and pp, and the procedure used by the REPL
+to print results). To preserve write/read invariance the printer and
+reader must be using compatible readtables. For example a symbol
+which contains upper case letters will be printed with special escapes
+if the readtable indicates that the reader is case-insensitive.
+
Readtables are immutable records whose fields specify various textual +representation aspects. There are accessor procedures to retrieve the +content of specific fields. There are also functional update +procedures that create a copy of a readtable, with a specific field +set to a new value. +
+ (readtable? obj) | procedure |
This procedure returns #t when obj is a readtable and
+#f otherwise.
+
For example: +
+> (readtable? (current-readtable)) +#t +> (readtable? 123) +#f + |
(readtable-case-conversion? readtable) | procedure |
(readtable-case-conversion?-set readtable new-value) | procedure |
The procedure readtable-case-conversion? returns the content of
+the case-conversion? field of readtable. When the
+content of this field is #f, the reader preserves the case of
+symbols and keyword objects that are read (i.e. Ice and
+ice are distinct symbols). When the content of this field is
+the symbol upcase, the reader converts lowercase letters to
+uppercase when reading symbols and keywords (i.e. Ice is read
+as the symbol (string->symbol "ICE")). Otherwise the reader
+converts uppercase letters to lowercase when reading symbols and
+keywords (i.e. Ice is read as the symbol (string->symbol
+"ice")).
+
The procedure readtable-case-conversion?-set returns a copy
+of readtable where only the case-conversion? field
+has been changed to new-value.
+
For example: +
+> (output-port-readtable-set! + (repl-output-port) + (readtable-case-conversion?-set + (output-port-readtable (repl-output-port)) + #f)) +> (input-port-readtable-set! + (repl-input-port) + (readtable-case-conversion?-set + (input-port-readtable (repl-input-port)) + #f)) +> 'Ice +Ice +> (input-port-readtable-set! + (repl-input-port) + (readtable-case-conversion?-set + (input-port-readtable (repl-input-port)) + #t)) +> 'Ice +ice +> (input-port-readtable-set! + (repl-input-port) + (readtable-case-conversion?-set + (input-port-readtable (repl-input-port)) + 'upcase)) +> 'Ice +ICE + |
(readtable-keywords-allowed? readtable) | procedure |
(readtable-keywords-allowed?-set readtable new-value) | procedure |
The procedure readtable-keywords-allowed? returns the content
+of the keywords-allowed? field of readtable. When the
+content of this field is #f, the reader does not recognize
+keyword objects (i.e. :foo and foo: are read as the
+symbols (string->symbol ":foo") and (string->symbol
+"foo:") respectively). When the content of this field is the symbol
+prefix, the reader recognizes keyword objects that start with a
+colon, as in Common Lisp (i.e. :foo is read as the keyword
+(string->keyword "foo")). Otherwise the reader recognizes
+keyword objects that end with a colon, as in DSSSL (i.e. foo:
+is read as the symbol (string->symbol "foo")).
+
The procedure readtable-keywords-allowed?-set returns a copy
+of readtable where only the keywords-allowed? field
+has been changed to new-value.
+
For example: +
+> (input-port-readtable-set! + (repl-input-port) + (readtable-keywords-allowed?-set + (input-port-readtable (repl-input-port)) + #f)) +> (map keyword? '(foo :foo foo:)) +(#f #f #f) +> (input-port-readtable-set! + (repl-input-port) + (readtable-keywords-allowed?-set + (input-port-readtable (repl-input-port)) + #t)) +> (map keyword? '(foo :foo foo:)) +(#f #f #t) +> (input-port-readtable-set! + (repl-input-port) + (readtable-keywords-allowed?-set + (input-port-readtable (repl-input-port)) + 'prefix)) +> (map keyword? '(foo :foo foo:)) +(#f #t #f) + |
(readtable-sharing-allowed? readtable) | procedure |
(readtable-sharing-allowed?-set readtable new-value) | procedure |
The procedure readtable-sharing-allowed? returns the content of
+the sharing-allowed? field of readtable. The reader
+recognizes the #n# and #n=datum
+notation for circular structures and the printer uses this notation if
+and only if the content of the sharing-allowed? field is not
+#f. Moreover when the content of the sharing-allowed?
+field is the symbol serialize, the printer uses a special
+external representation that the reader understands and that extends
+write/read invariance to the following types: records, procedures and
+continuations. Note that an object can be serialized and deserialized
+if and only if all of its components are serializable.
+
The procedure readtable-sharing-allowed?-set returns a copy
+of readtable where only the sharing-allowed? field
+has been changed to new-value.
+
Here is a simple example: +
+> (define (wr obj allow?) + (call-with-output-string + '() + (lambda (p) + (output-port-readtable-set! + p + (readtable-sharing-allowed?-set + (output-port-readtable p) + allow?)) + (write obj p)))) +> (define (rd str allow?) + (call-with-input-string + str + (lambda (p) + (input-port-readtable-set! + p + (readtable-sharing-allowed?-set + (input-port-readtable p) + allow?)) + (read p)))) +> (define x (list 1 2 3)) +> (set-car! (cdr x) (cddr x)) +> (wr x #f) +"(1 (3) 3)" +> (wr x #t) +"(1 #0=(3) . #0#)" +> (define y (rd (wr x #t) #t)) +> y +(1 (3) 3) +> (eq? (cadr y) (cddr y)) +#t +> (define f #f) +> (let ((free (expt 2 10))) + (set! f (lambda (x) (+ x free)))) +> (define s (wr f 'serialize)) +> (string-length s) +4196 +> (define g (rd s 'serialize)) +> (eq? f g) +#f +> (g 4) +1028 + |
Continuations are tricky to serialize because they contain a dynamic
+environment and this dynamic environment may contain non-serializable
+objects, in particular ports attached to operating-system streams such
+as files, the console or standard input/output. Indeed, all dynamic
+environments contain a binding for the current-input-port and
+current-output-port. Moreover, any thread that has started a
+REPL has a continuation which refers to the repl-context object
+in its dynamic environment. A repl-context object contains the
+interaction channel, which is typically connected to a
+non-serializable port, such as the console. Another problem is that
+the parameterize form saves the old binding of the parameter in
+the continuation, so it is not possible to eliminate the references to
+these ports in the continuation by using the parameterize form
+alone.
+
Serialization of continuations can be achieved dependably by taking
+advantage of string-ports, which are serializable objects (unless
+there is a blocked thread), and the following features of threads:
+they inherit the dynamic environment of the parent thread and they
+start with an initial continuation that contains only serializable
+objects. So a thread created in a dynamic environment where
+current-input-port and current-output-port are bound to
+a dummy string-port has a serializable continuation.
+
Here is an example where continuations are serialized: +
+> (define (wr obj) + (call-with-output-string + '() + (lambda (p) + (output-port-readtable-set! + p + (readtable-sharing-allowed?-set + (output-port-readtable p) + 'serialize)) + (write obj p)))) +> (define (rd str) + (call-with-input-string + str + (lambda (p) + (input-port-readtable-set! + p + (readtable-sharing-allowed?-set + (input-port-readtable p) + 'serialize)) + (read p)))) +> (define fifo (open-vector)) +> (define (suspend-and-die!) + (call-with-current-continuation + (lambda (k) + (write (wr k) fifo) + (newline fifo) + (force-output fifo) + (thread-terminate! (current-thread))))) +> (let ((dummy-port (open-string))) + (parameterize ((current-input-port dummy-port) + (current-output-port dummy-port)) + (thread-start! + (make-thread + (lambda () + (* 100 + (suspend-and-die!))))))) +#<thread #2> +> (define s (read fifo)) +> (thread-join! + (thread-start! + (make-thread + (lambda () + ((rd s) 111))))) +11100 +> (thread-join! + (thread-start! + (make-thread + (lambda () + ((rd s) 222))))) +22200 +> (string-length s) +13114 + |
(readtable-eval-allowed? readtable) | procedure |
(readtable-eval-allowed?-set readtable new-value) | procedure |
The procedure readtable-eval-allowed? returns the content of
+the eval-allowed? field of readtable. The reader
+recognizes the #.expression notation for read-time
+evaluation if and only if the content of the eval-allowed?
+field is not #f.
+
The procedure readtable-eval-allowed?-set returns a copy
+of readtable where only the eval-allowed? field
+has been changed to new-value.
+
For example: +
+> (input-port-readtable-set! + (repl-input-port) + (readtable-eval-allowed?-set + (input-port-readtable (repl-input-port)) + #t)) +> '(5 plus 7 is #.(+ 5 7)) +(5 plus 7 is 12) +> '(buf = #.(make-u8vector 25)) +(buf = #u8(0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0)) + |
(readtable-write-cdr-read-macros? readtable) | procedure |
(readtable-write-cdr-read-macros?-set readtable new-value) | procedure |
(readtable-write-extended-read-macros? readtable) | procedure |
(readtable-write-extended-read-macros?-set readtable new-value) | procedure |
The procedure readtable-write-cdr-read-macros? returns the
+content of the write-cdr-read-macros? field of readtable.
+The procedure readtable-write-extended-read-macros? returns the
+content of the write-extended-read-macros? field of
+readtable.
+
At all times the printer uses read-macros in its output for datums of
+the form (quote datum), (quasiquote datum),
+(unquote datum), and (unquote-splicing
+datum). That is the following read-macro notations will be
+used respectively: 'datum, `datum,
+,datum, and ,@datum. Moreover, normally
+the read-macros will not be used when the form appears in the cdr of a
+list, for example (foo quote bar), (foo . (quote bar))
+and (foo . 'bar) will all be printed as (foo quote bar).
+
When the content of the write-cdr-read-macros? field is not
+#f, the printer will use read-macros when the forms appear in
+the cdr of a list. For example (foo quote bar) will be printed
+as (foo . 'bar). When the content of the
+write-extended-read-macros? field is not #f, the printer
+will also use extended read-macros, for example #'datum
+in place of (syntax datum).
+
The procedure readtable-write-cdr-read-macros?-set returns a
+copy of readtable where only the write-cdr-read-macros?
+field has been changed to new-value. The procedure
+readtable-write-extended-read-macros?-set returns a copy of
+readtable where only the write-extended-read-macros?
+field has been changed to new-value.
+
For example: +
+> (output-port-readtable-set! + (repl-output-port) + (readtable-write-extended-read-macros?-set + (output-port-readtable (repl-output-port)) + #t)) +> '(foo (syntax bar)) +(foo #'bar) +> '(foo syntax bar) +(foo syntax bar) +> (output-port-readtable-set! + (repl-output-port) + (readtable-write-cdr-read-macros?-set + (output-port-readtable (repl-output-port)) + #t)) +> '(foo syntax bar) +(foo . #'bar) + |
(readtable-max-write-level readtable) | procedure |
(readtable-max-write-level-set readtable new-value) | procedure |
The procedure readtable-max-write-level returns the content of
+the max-write-level field of readtable. The printer will
+display an ellipsis for the elements of lists and vectors that are
+nested deeper than this level.
+
The procedure readtable-max-write-level-set returns a copy
+of readtable where only the max-write-level field
+has been changed to new-value, which must be an nonnegative
+fixnum.
+
For example: +
+> (define (wr obj n) + (call-with-output-string + '() + (lambda (p) + (output-port-readtable-set! + p + (readtable-max-write-level-set + (output-port-readtable p) + n)) + (write obj p)))) +> (wr '(a #(b (c c) #u8(9 9 9) b) a) 3) +"(a #(b (c c) #u8(9 9 9) b) a)" +> (wr '(a #(b (c c) #u8(9 9 9) b) a) 2) +"(a #(b (...) #u8(...) b) a)" +> (wr '(a #(b (c c) #u8(9 9 9) b) a) 1) +"(a #(...) a)" +> (wr '(a #(b (c c) #u8(9 9 9) b) a) 0) +"(...)" +> (wr 'hello 0) +"hello" + |
(readtable-max-write-length readtable) | procedure |
(readtable-max-write-length-set readtable new-value) | procedure |
The procedure readtable-max-write-length returns the content of
+the max-write-length field of readtable. The printer will
+display an ellipsis for the elements of lists and vectors that are at
+an index beyond that length.
+
The procedure readtable-max-write-length-set returns a copy
+of readtable where only the max-write-length field
+has been changed to new-value, which must be an nonnegative
+fixnum.
+
For example: +
+> (define (wr obj n) + (call-with-output-string + '() + (lambda (p) + (output-port-readtable-set! + p + (readtable-max-write-length-set + (output-port-readtable p) + n)) + (write obj p)))) +> (wr '(a #(b (c c) #u8(9 9 9) b) . a) 4) +"(a #(b (c c) #u8(9 9 9) b) . a)" +> (wr '(a #(b (c c) #u8(9 9 9) b) . a) 3) +"(a #(b (c c) #u8(9 9 9) ...) . a)" +> (wr '(a #(b (c c) #u8(9 9 9) b) . a) 2) +"(a #(b (c c) ...) . a)" +> (wr '(a #(b (c c) #u8(9 9 9) b) . a) 1) +"(a ...)" +> (wr '(a #(b (c c) #u8(9 9 9) b) . a) 0) +"(...)" + |
(readtable-max-unescaped-char readtable) | procedure |
(readtable-max-unescaped-char-set readtable new-value) | procedure |
The procedure readtable-max-unescaped-char returns the content
+of the max-unescaped-char field of readtable. The
+printer will display using an escape sequence any character within
+symbols, strings and character objects greater than
+max-unescaped-char
+
The procedure readtable-max-unescaped-char-set returns a copy
+of readtable where only the max-unescaped-char field
+has been changed to new-value, which must be a character.
+
For example: +
+> (define rt (output-port-readtable (repl-output-port))) +> (readtable-max-unescaped-char rt) +#\delete +> (string (integer->char 233)) +"\351" +> (define (f c) + (with-output-to-string + (list readtable: (readtable-max-unescaped-char-set rt c)) + (lambda () (write (string (integer->char 233)))))) +> (f #\delete) +"\"\\351\"" +> (string-length (f #\delete)) +6 +> (f #\U0010ffff) +"\"\351\"" +> (string-length (f #\U0010ffff)) +3 +> (output-port-readtable-set! + (repl-output-port) + (readtable-max-unescaped-char-set rt #\U0010ffff)) +> (string (integer->char 233)) +"é" + |
(readtable-start-syntax readtable) | procedure |
(readtable-start-syntax-set readtable new-value) | procedure |
The procedure readtable-start-syntax returns the content of the
+start-syntax field of readtable. The reader uses this
+field to determine in which syntax to start parsing the input. When
+the content of this field is the symbol six, the reader starts
+in the infix syntax. Otherwise the reader starts in the prefix
+syntax.
+
The procedure readtable-start-syntax-set returns a copy
+of readtable where only the start-syntax field
+has been changed to new-value.
+
For example: +
+> (+ 2 3) +5 +> (input-port-readtable-set! + (repl-input-port) + (readtable-start-syntax-set + (input-port-readtable (repl-input-port)) + 'six)) +> 2+3; +5 +> exit(); + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
Booleans are required to be followed by a delimiter
+(i.e. #f64() is not the boolean #f followed by the
+number 64 and the empty list).
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
Characters are required to be followed by a delimiter
+(i.e. #\spaceballs is not the character #\space followed
+by the symbol balls). The lexical syntax of characters is
+extended to allow the following:
+
#\nulUnicode character 0 +
#\alarmUnicode character 7 +
#\backspaceUnicode character 8 +
#\tabUnicode character 9 +
#\newlineUnicode character 10 (newline character) +
#\linefeedUnicode character 10 +
#\vtabUnicode character 11 +
#\pageUnicode character 12 +
#\returnUnicode character 13 +
#\escUnicode character 27 +
#\spaceUnicode character 32 (space character) +
#\deleteUnicode character 127 +
#\xhhcharacter encoded in hexadecimal (>= 1 hexadecimal digit) +
#\uhhhhcharacter encoded in hexadecimal (exactly 4 hexadecimal digits) +
#\Uhhhhhhhhcharacter encoded in hexadecimal (exactly 8 hexadecimal digits) +
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The lexical syntax of quoted strings is extended to allow the following +escape codes: +
+\aUnicode character 7 +
\bUnicode character 8 +
\tUnicode character 9 +
\nUnicode character 10 (newline character) +
\vUnicode character 11 +
\fUnicode character 12 +
\rUnicode character 13 +
\""
+
\\\
+
\||
+
\??
+
\ooocharacter encoded in octal (1 to 3 octal digits, first digit must be less +than 4 when there are 3 octal digits) +
\xhhcharacter encoded in hexadecimal (>= 1 hexadecimal digit) +
\uhhhhcharacter encoded in hexadecimal (exactly 4 hexadecimal digits) +
\Uhhhhhhhhcharacter encoded in hexadecimal (exactly 8 hexadecimal digits) +
\<space>Unicode character 32 (space character) +
\<newline><whitespace-except-newline>*This sequence expands to nothing (it is useful for splitting a long +string literal on multiple lines while respecting proper indentation +of the source code) +
Gambit also supports a “here string” syntax that is similar +to shell “here documents”. For example: +
+> (pretty-print #<<THE-END +hello +world +THE-END +) +"hello\nworld" + |
The here string starts with the sequence #<<. The part of the +line after the #<< up to and including the newline character is +the key. The first line afterward that matches the key marks the end +of the here string. The string contains all the characters between +the start key and the end key, with the exception of the newline +character before the end key. +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The lexical syntax of symbols is extended to allow a leading and
+trailing vertical bar (e.g. |a\|b"c:|). The symbol’s name
+corresponds verbatim to the characters between the vertical bars
+except for escaped characters. The same escape sequences as for
+strings are permitted except that " does not need to be escaped
+and | needs to be escaped.
+
For example: +
+> (symbol->string '|a\|b"c:|) +"a|b\"c:" + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The lexical syntax of keywords is like symbols, but with a colon at
+the end (note that this can be changed to a leading colon by setting
+the keywords-allowed? field of the readtable to the symbol
+prefix). A colon by itself is not a keyword, it is a symbol.
+Vertical bars can be used like symbols but the colon must be outside
+the vertical bars. Note that the string returned by the
+keyword->string procedure does not include the colon.
+
For example: +
+> (keyword->string 'foo:) +"foo" +> (map keyword? '(|ab()cd:| |ab()cd|: : ||:)) +(#f #t #f #t) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The lexical syntax of boxes is #&obj where obj is the
+content of the box.
+
For example: +
+> (list '#&"hello" '#&123) +(#&"hello" #&123) +> (box (box (+ 10 20))) +#&#&30 + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The lexical syntax of the special inexact real numbers is as follows: +
++inf.0positive infinity +
-inf.0negative infinity +
+nan.0“not a number” +
-0.negative zero (0. is the positive zero) +
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
Homogeneous vectors are vectors containing raw numbers of the same +type (signed or unsigned exact integers or inexact reals). There are +10 types of homogeneous vectors: +s8vector (vector of 8 bit signed integers), +u8vector (vector of 8 bit unsigned integers), +s16vector (vector of 16 bit signed integers), +u16vector (vector of 16 bit unsigned integers), +s32vector (vector of 32 bit signed integers), +u32vector (vector of 32 bit unsigned integers), +s64vector (vector of 64 bit signed integers), +u64vector (vector of 64 bit unsigned integers), +f32vector (vector of 32 bit floating point numbers), +and f64vector (vector of 64 bit floating point numbers). +
+The external representation of homogeneous vectors is similar to +normal vectors but with the #( prefix replaced respectively +with +#s8(, #u8(, +#s16(, #u16(, +#s32(, #u32(, +#s64(, #u64(, +#f32(, and #f64(. +
+The elements of the integer homogeneous vectors must be exact integers +fitting in the given precision. The elements of the floating point +homogeneous vectors must be inexact reals. +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
#! syntaxThe lexical syntax of the special #! objects is as follows:
+
#!eofend-of-file object +
#!voidvoid object +
#!optionaloptional object +
#!restrest object +
#!keykey object +
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
Multiline comments are delimited by the tokens #| and |#. +These comments can be nested. +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The reader supports an infix syntax extension which is called SIX +(Scheme Infix eXtension). This extension is both supported by the +read procedure and in program source code. +
+The backslash character is a delimiter that marks the beginning of a +single datum expressed in the infix syntax (the details are given +below). One way to think about it is that the backslash character +escapes the prefix syntax temporarily to use the infix syntax. For +example a three element list could be written as (X +\Y Z), the elements X and Z are expressed +using the normal prefix syntax and Y is expressed using the +infix syntax. +
+When the reader encounters an infix datum, it constructs a syntax tree +for that particular datum. Each node of this tree is represented with +a list whose first element is a symbol indicating the type of node. +For example, (six.identifier abc) is the representation of the +infix identifier abc and (six.index (six.identifier abc) +(six.identifier i)) is the representation of the infix datum +abc[i];. +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The SIX grammar is given below. On the left hand side are the +production rules. On the right hand side is the datum that is +constructed by the reader. The notation $i denotes the datum +that is constructed by the reader for the ith part of the +production rule. +
+ + + + +| <infix datum> ::= | |
| <stat> | $1 |
| <stat> ::= | |
| <if stat> | $1 |
| | <for stat> | $1 |
| | <while stat> | $1 |
| | <do stat> | $1 |
| | <switch stat> | $1 |
| | <case stat> | $1 |
| | <break stat> | $1 |
| | <continue stat> | $1 |
| | <label stat> | $1 |
| | <goto stat> | $1 |
| | <return stat> | $1 |
| | <expression stat> | $1 |
| | <procedure definition> | $1 |
| <variable definition> ; | $1 |
| | <clause stat> | $1 |
| | <compound stat> | $1 |
| ; | (six.compound) |
| <if stat> ::= | |
if ( <pexpr> ) <stat> | (six.if $3 $5) |
| if ( <pexpr> ) <stat> else <stat> | (six.if $3 $5 $7) |
| <for stat> ::= | |
for ( <stat> ; <oexpr> ; <oexpr> ) <stat> | (six.for $3 $5 $7 $9) |
| <while stat> ::= | |
while ( <pexpr> ) <stat> | (six.while $3 $5) |
| <do stat> ::= | |
do <stat> while ( <pexpr> ) ; | (six.do-while $2 $5) |
| <switch stat> ::= | |
switch ( <pexpr> ) <stat> | (six.switch $3 $5) |
| <case stat> ::= | |
case <expr> : <stat> | (six.case $2 $4) |
| <break stat> ::= | |
break ; | (six.break) |
| <continue stat> ::= | |
continue ; | (six.continue) |
| <label stat> ::= | |
<identifier> : <stat> | (six.label $1 $3) |
| <goto stat> ::= | |
goto <expr> ; | (six.goto $2) |
| <return stat> ::= | |
return ; | (six.return) |
| return <expr> ; | (six.return $2) |
| <expression stat> ::= | |
<expr> ; | $1 |
| <clause stat> ::= | |
<expr> . | (six.clause $1) |
| <pexpr> ::= | |
| <procedure definition> | $1 |
| | <variable definition> | $1 |
| | <expr> | $1 |
| <procedure definition> ::= | |
<type> <id-or-prefix> ( <parameters> ) <body> | (six.define-procedure $2 (six.procedure $1 $4 $6)) |
| <variable definition> ::= | |
| <type> <id-or-prefix> <dimensions> <iexpr> | (six.define-variable $2 $1 $3 $4) |
| <iexpr> ::= | |
= <expr> | $2 |
| | | #f |
| <dimensions> ::= | |
| [ <expr> ] <dimensions> | ($2 . $4) |
| | | () |
| <oexpr> ::= | |
| <expr> | $1 |
| | | #f |
| <expr> ::= | |
| <expr18> | $1 |
| <expr18> ::= | |
<expr17> :- <expr18> | (six.x:-y $1 $3) |
| | <expr17> | $1 |
| <expr17> ::= | |
<expr17> , <expr16> | (|six.x,y| $1 $3) |
| | <expr16> | $1 |
| <expr16> ::= | |
<expr15> := <expr16> | (six.x:=y $1 $3) |
| | <expr15> | $1 |
| <expr15> ::= | |
<expr14> %= <expr15> | (six.x%=y $1 $3) |
| <expr14> &= <expr15> | (six.x&=y $1 $3) |
| <expr14> *= <expr15> | (six.x*=y $1 $3) |
| <expr14> += <expr15> | (six.x+=y $1 $3) |
| <expr14> -= <expr15> | (six.x-=y $1 $3) |
| <expr14> /= <expr15> | (six.x/=y $1 $3) |
| <expr14> <<= <expr15> | (six.x<<=y $1 $3) |
| <expr14> = <expr15> | (six.x=y $1 $3) |
| <expr14> >>= <expr15> | (six.x>>=y $1 $3) |
| <expr14> ^= <expr15> | (six.x^=y $1 $3) |
| <expr14> |= <expr15> | (|six.x\|=y| $1 $3) |
| | <expr14> | $1 |
| <expr14> ::= | |
<expr13> : <expr14> | (six.x:y $1 $3) |
| | <expr13> | $1 |
| <expr13> ::= | |
<expr12> ? <expr> : <expr13> | (six.x?y:z $1 $3 $5) |
| | <expr12> | $1 |
| <expr12> ::= | |
<expr12> || <expr11> | (|six.x\|\|y| $1 $3) |
| | <expr11> | $1 |
| <expr11> ::= | |
<expr11> && <expr10> | (six.x&&y $1 $3) |
| | <expr10> | $1 |
| <expr10> ::= | |
<expr10> | <expr9> | (|six.x\|y| $1 $3) |
| | <expr9> | $1 |
| <expr9> ::= | |
<expr9> ^ <expr8> | (six.x^y $1 $3) |
| | <expr8> | $1 |
| <expr8> ::= | |
<expr8> & <expr7> | (six.x&y $1 $3) |
| | <expr7> | $1 |
| <expr7> ::= | |
<expr7> != <expr6> | (six.x!=y $1 $3) |
| <expr7> == <expr6> | (six.x==y $1 $3) |
| | <expr6> | $1 |
| <expr6> ::= | |
<expr6> < <expr5> | (six.x<y $1 $3) |
| <expr6> <= <expr5> | (six.x<=y $1 $3) |
| <expr6> > <expr5> | (six.x>y $1 $3) |
| <expr6> >= <expr5> | (six.x>=y $1 $3) |
| | <expr5> | $1 |
| <expr5> ::= | |
<expr5> << <expr4> | (six.x<<y $1 $3) |
| <expr5> >> <expr4> | (six.x>>y $1 $3) |
| | <expr4> | $1 |
| <expr4> ::= | |
<expr4> + <expr3> | (six.x+y $1 $3) |
| <expr4> - <expr3> | (six.x-y $1 $3) |
| | <expr3> | $1 |
| <expr3> ::= | |
<expr3> % <expr2> | (six.x%y $1 $3) |
| <expr3> * <expr2> | (six.x*y $1 $3) |
| <expr3> / <expr2> | (six.x/y $1 $3) |
| | <expr2> | $1 |
| <expr2> ::= | |
& <expr2> | (six.&x $2) |
| + <expr2> | (six.+x $2) |
| - <expr2> | (six.-x $2) |
| * <expr2> | (six.*x $2) |
| ! <expr2> | (six.!x $2) |
| ! | (six.!) |
| ++ <expr2> | (six.++x $2) |
| -- <expr2> | (six.--x $2) |
| ~ <expr2> | (six.~x $2) |
| new <id-or-prefix> ( <arguments> ) | (six.new $2 . $4) |
| | <expr1> | $1 |
| <expr1> ::= | |
<expr1> ++ | (six.x++ $1) |
| <expr1> -- | (six.x-- $1) |
| <expr1> ( <arguments> ) | (six.call $1 . $3) |
| <expr1> [ <expr> ] | (six.index $1 $3) |
| <expr1> -> <id-or-prefix> | (six.arrow $1 $3) |
| <expr1> . <id-or-prefix> | (six.dot $1 $3) |
| | <expr0> | $1 |
| <expr0> ::= | |
| <id-or-prefix> | $1 |
| | <string> | (six.literal $1) |
| | <char> | (six.literal $1) |
| | <number> | (six.literal $1) |
| ( <expr> ) | $2 |
| ( <block stat> ) | $2 |
| | <datum-starting-with-#-or-backquote> | (six.prefix $1) |
| [ <elements> ] | $2 |
| <type> ( <parameters> ) <body> | (six.procedure $1 $3 $5) |
| <block stat> ::= | |
{ <stat list> } | (six.compound . $2) |
| <body> ::= | |
{ <stat list> } | (six.procedure-body . $2) |
| <stat list> ::= | |
| <stat> <stat list> | ($1 . $2) |
| | | () |
| <parameters> ::= | |
| <nonempty parameters> | $1 |
| | | () |
| <nonempty parameters> ::= | |
<parameter> , <nonempty parameters> | ($1 . $3) |
| | <parameter> | ($1) |
| <parameter> ::= | |
| <type> <id-or-prefix> | ($2 $1) |
| <arguments> ::= | |
| <nonempty arguments> | $1 |
| | | () |
| <nonempty arguments> ::= | |
<expr> , <nonempty arguments> | ($1 . $3) |
| | <expr> | ($1) |
| <elements> ::= | |
| <nonempty elements> | $1 |
| | | (six.null) |
| <nonempty elements> ::= | |
| <expr> | (six.list $1 (six.null)) |
| <expr> , <nonempty elements> | (six.list $1 $3) |
| <expr> | <expr> | (six.cons $1 $3) |
| <id-or-prefix> ::= | |
| <identifier> | (six.identifier $1) |
| \ <datum> | (six.prefix $2) |
| <type> ::= | |
int | int |
| char | char |
| bool | bool |
| void | void |
| float | float |
| double | double |
| obj | obj |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The semantics of SIX depends on the definition of the
+six.XXX identifiers (as functions and macros). Many of
+these identifiers are predefined macros which give SIX a semantics
+that is close to C’s. The user may override these definitions to
+change the semantics either globally or locally. For example,
+six.x^y is a predefined macro that expands (six.x^y x y)
+into (bitwise-xor x y). If the user prefers the ^
+operator to express exponentiation in a specific function, then in
+that function six.x^y can be redefined as a macro that expands
+(six.x^y x y) into (expt x y). Note that the
+associativity and precedence of operators cannot be changed as that is
+a syntactic issue.
+
Note that the following identifiers are not predefined, and
+consequently they do not have a predefined semantics:
+six.label, six.goto, six.switch, six.case,
+six.break, six.continue, six.return,
+six.clause, six.x:-y, and six.!.
+
The following is an example showing some of the predefined semantics +of SIX: +
+> (list (+ 1 2) \3+4; (+ 5 6))
+(3 7 11)
+> \[ 1+2, \(+ 3 4), 5+6 ];
+(3 7 11)
+> (map (lambda (x) \(x*x-1)/log(x+1);) '(1 2 3 4))
+(0 2.730717679880512 5.7707801635558535 9.320024018394177)
+> \obj n = expt(10,5);
+> n
+100000
+> \obj t[3][10] = 88;
+> \t[0][9] = t[2][1] = 11;
+11
+> t
+#(#(88 88 88 88 88 88 88 88 88 11)
+ #(88 88 88 88 88 88 88 88 88 88)
+ #(88 11 88 88 88 88 88 88 88 88))
+> \obj radix = new parameter (10);
+> \radix(2);
+> \radix();
+2
+> \for (int i=0; i<5; i++) pp(1<<i*8);
+1
+256
+65536
+16777216
+4294967296
+> \obj \make-adder (obj x) { obj (obj y) { x+y; }; }
+> \map (new adder (100), [1,2,3,4]);
+(101 102 103 104)
+> (map (make-adder 100) (list 1 2 3 4))
+(101 102 103 104)
+ |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The Gambit Scheme system offers a mechanism for interfacing Scheme code +and C code called the “C-interface”. A Scheme program indicates which +C functions it needs to have access to and which Scheme procedures can +be called from C, and the C interface automatically constructs the +corresponding Scheme procedures and C functions. The conversions needed +to transform data from the Scheme representation to the C representation +(and back), are generated automatically in accordance with the argument +and result types of the C function or Scheme procedure. +
+The C-interface places some restrictions on the types of data that can +be exchanged between C and Scheme. The mapping of data types between C +and Scheme is discussed in the next section. The remaining sections of +this chapter describe each special form of the C-interface. +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
Scheme and C do not provide the same set of built-in data types so it is +important to understand which Scheme type is compatible with which C +type and how values get mapped from one environment to the other. To +improve compatibility a new type is added to Scheme, the foreign +object type, and the following data types are added to C: +
+scheme-objectdenotes the universal type of Scheme objects
+(type ___SCMOBJ defined in gambit.h)
+
booldenotes the C++ bool type or the C int type
+(type ___BOOL defined in gambit.h)
+
int88 bit signed integer (type ___S8 defined in gambit.h)
+
unsigned-int88 bit unsigned integer (type ___U8 defined in gambit.h)
+
int1616 bit signed integer (type ___S16 defined in gambit.h)
+
unsigned-int1616 bit unsigned integer (type ___U16 defined in gambit.h)
+
int3232 bit signed integer (type ___S32 defined in gambit.h)
+
unsigned-int3232 bit unsigned integer (type ___U32 defined in gambit.h)
+
int6464 bit signed integer (type ___S64 defined in gambit.h)
+
unsigned-int6464 bit unsigned integer (type ___U64 defined in gambit.h)
+
float3232 bit floating point number (type ___F32 defined in gambit.h)
+
float6464 bit floating point number (type ___F64 defined in gambit.h)
+
ISO-8859-1denotes ISO-8859-1 encoded characters
+(8 bit unsigned integer, type ___ISO_8859_1 defined in gambit.h)
+
UCS-2denotes UCS-2 encoded characters
+(16 bit unsigned integer, type ___UCS_2 defined in gambit.h)
+
UCS-4denotes UCS-4 encoded characters
+(32 bit unsigned integer, type ___UCS_4 defined in gambit.h)
+
char-stringdenotes the C char* type when used as a null terminated string +
nonnull-char-stringdenotes the nonnull C char* type when used as a null terminated string +
nonnull-char-string-listdenotes an array of nonnull C char* terminated with a null pointer +
ISO-8859-1-stringdenotes ISO-8859-1 encoded strings
+(null terminated string of 8 bit unsigned integers, i.e. ___ISO_8859_1*)
+
nonnull-ISO-8859-1-stringdenotes nonnull ISO-8859-1 encoded strings
+(null terminated string of 8 bit unsigned integers, i.e. ___ISO_8859_1*)
+
nonnull-ISO-8859-1-stringlistdenotes an array of nonnull ISO-8859-1 encoded strings terminated with a null pointer +
UTF-8-stringdenotes UTF-8 encoded strings
+(null terminated string of char, i.e. char*)
+
nonnull-UTF-8-stringdenotes nonnull UTF-8 encoded strings
+(null terminated string of char, i.e. char*)
+
nonnull-UTF-8-string-listdenotes an array of nonnull UTF-8 encoded strings terminated with a null pointer +
UTF-16-stringdenotes UTF-16 encoded strings
+(null terminated string of char, i.e. char*)
+
nonnull-UTF-16-stringdenotes nonnull UTF-16 encoded strings
+(null terminated string of char, i.e. char*)
+
nonnull-UTF-16-string-listdenotes an array of nonnull UTF-16 encoded strings terminated with a null pointer +
UCS-2-stringdenotes UCS-2 encoded strings
+(null terminated string of 16 bit unsigned integers, i.e. ___UCS_2*)
+
nonnull-UCS-2-stringdenotes nonnull UCS-2 encoded strings
+(null terminated string of 16 bit unsigned integers, i.e. ___UCS_2*)
+
nonnull-UCS-2-string-listdenotes an array of nonnull UCS-2 encoded strings terminated with a null pointer +
UCS-4-stringdenotes UCS-4 encoded strings
+(null terminated string of 32 bit unsigned integers, i.e. ___UCS_4*)
+
nonnull-UCS-4-stringdenotes nonnull UCS-4 encoded strings
+(null terminated string of 32 bit unsigned integers, i.e. ___UCS_4*)
+
nonnull-UCS-4-string-listdenotes an array of nonnull UCS-4 encoded strings terminated with a null pointer +
wchar_t-stringdenotes wchar_t encoded strings
+(null terminated string of wchar_t, i.e. wchar_t*)
+
nonnull-wchar_t-stringdenotes nonnull wchar_t encoded strings
+(null terminated string of wchar_t, i.e. wchar_t*)
+
nonnull-wchar_t-string-listdenotes an array of nonnull wchar_t encoded strings terminated with a null pointer
+
To specify a particular C type inside the c-lambda,
+c-define and c-define-type forms, the following “Scheme
+notation” is used:
+
Scheme notationC type +
voidvoid
+
boolbool
+
charchar (may be signed or unsigned depending on the C compiler)
+
signed-charsigned char
+
unsigned-charunsigned char
+
ISO-8859-1ISO-8859-1
+
UCS-2UCS-2
+
UCS-4UCS-4
+
wchar_twchar_t
+
shortshort
+
unsigned-shortunsigned short
+
intint
+
unsigned-intunsigned int
+
longlong
+
unsigned-longunsigned long
+
long-longlong long
+
unsigned-long-longunsigned long long
+
floatfloat
+
doubledouble
+
int8int8
+
unsigned-int8unsigned-int8
+
int16int16
+
unsigned-int16unsigned-int16
+
int32int32
+
unsigned-int32unsigned-int32
+
int64int64
+
unsigned-int64unsigned-int64
+
float32float32
+
float64float64
+
(struct "c-struct-id" [tags [release-function]])struct c-struct-id (where c-struct-id is the name of a
+C structure; see below for the meaning of tags and release-function)
+
(union "c-union-id" [tags [release-function]])union c-union-id (where c-union-id is the name of a
+C union; see below for the meaning of tags and release-function)
+
(type "c-type-id" [tags [release-function]])c-type-id (where c-type-id is an identifier naming a
+C type; see below for the meaning of tags and release-function)
+
(pointer type [tags [release-function]])T* (where T is the C equivalent of type
+which must be the Scheme notation of a C type; see below for the meaning
+of tags and release-function)
+
(nonnull-pointer type [tags [release-function]])same as (pointer type [tags [release-function]])
+except the NULL pointer is not allowed
+
(function (type1…) result-type)function with the given argument types and result type +
(nonnull-function (type1…) result-type)same as (function (type1…) result-type)
+except the NULL pointer is not allowed
+
char-stringchar-string
+
nonnull-char-stringnonnull-char-string
+
nonnull-char-string-listnonnull-char-string-list
+
ISO-8859-1-stringISO-8859-1-string
+
nonnull-ISO-8859-1-stringnonnull-ISO-8859-1-string
+
nonnull-ISO-8859-1-string-listnonnull-ISO-8859-1-string-list
+
UTF-8-stringUTF-8-string
+
nonnull-UTF-8-stringnonnull-UTF-8-string
+
nonnull-UTF-8-string-listnonnull-UTF-8-string-list
+
UTF-16-stringUTF-16-string
+
nonnull-UTF-16-stringnonnull-UTF-16-string
+
nonnull-UTF-16-string-listnonnull-UTF-16-string-list
+
UCS-2-stringUCS-2-string
+
nonnull-UCS-2-stringnonnull-UCS-2-string
+
nonnull-UCS-2-string-listnonnull-UCS-2-string-list
+
UCS-4-stringUCS-4-string
+
nonnull-UCS-4-stringnonnull-UCS-4-string
+
nonnull-UCS-4-string-listnonnull-UCS-4-string-list
+
wchar_t-stringwchar_t-string
+
nonnull-wchar_t-stringnonnull-wchar_t-string
+
nonnull-wchar_t-string-listnonnull-wchar_t-string-list
+
scheme-objectscheme-object
+
nameappropriate translation of name (where name
+is a C type defined with c-define-type)
+
"c-type-id"c-type-id (this form is equivalent to (type "c-type-id"))
+
The struct, union, type, pointer and
+nonnull-pointer types are “foreign types” and they are
+represented on the Scheme side as “foreign objects”. A foreign object
+is internally represented as a pointer. This internal pointer is
+identical to the C pointer being represented in the case of the
+pointer and nonnull-pointer types.
+
In the case of the struct, union and type types,
+the internal pointer points to a copy of the C data type being
+represented. When an instance of one of these types is converted from C
+to Scheme, a block of memory is allocated from the C heap and
+initialized with the instance and then a foreign object is allocated
+from the Scheme heap and initialized with the pointer to this copy.
+This approach may appear overly complex, but it allows the conversion of
+C++ classes that do not have a zero parameter constructor or an
+assignment method (i.e. when compiling with a C++ compiler an instance
+is copied using new type (instance), which calls the
+copy-constructor of type if it is a class; type’s assignment
+operator is never used). Conversion from Scheme to C simply
+dereferences the internal pointer (no allocation from the C heap is
+performed). Deallocation of the copy on the C heap is under the control
+of the release function attached to the foreign object (see below).
+
The optional tags field of foreign type specifications is used
+for type checking on the Scheme side. The tags field must be
+#f, a symbol or a non-empty list of symbols. When it is not
+specified the tags field defaults to a symbol whose name, as
+returned by symbol->string, is the C type declaration for that
+type. For example the symbol char** is the default for the
+type (pointer (pointer char)). A tags field that is a
+single symbol is equivalent to a list containing only that symbol.
+The first symbol in the list of tags is the primary tag. For example
+the primary tag of the type (pointer char) is char* and
+the primary tag of the type (pointer char (foo bar)) is
+foo.
+
Type compatibility between two foreign types depends on their tags. +An instance of a foreign type T can be used where a foreign type +E is expected if and only if +
+#f, or
+
+#f, or
+
+For the safest code a tags field of #f should be used
+sparingly, as it completely bypasses type checking. The external
+representation of Scheme foreign objects (used by the write
+procedure) contains the primary tag (if the tags field is not
+#f), and the hexadecimal address denoted by the internal
+pointer, for example #<char** #2 0x2AAC535C>. Note that the
+hexadecimal address is in C notation, which can be easily transferred
+to a C debugger with a “cut-and-paste”.
+
A release-function can also be specified within a foreign type
+specification. The release-function must be #f or a string
+naming a C function with a single parameter of type void* (in
+which the internal pointer is passed) and with a result of type
+___SCMOBJ (for returning an error code). When the
+release-function is not specified or is #f a default
+function is constructed by the C-interface. This default function does
+nothing in the case of the pointer and nonnull-pointer
+types (deallocation is not the responsibility of the C-interface) and
+returns the fixnum ___FIX(___NO_ERR) to indicate no error. In
+the case of the struct, union and type types, the
+default function reclaims the copy on the C heap referenced by the
+internal pointer (when using a C++ compiler this is done using
+delete (type*)internal-pointer, which calls the
+destructor of type if it is a class) and returns
+___FIX(___NO_ERR). In many situations the default
+release-function will perform the appropriate cleanup for the
+foreign type. However, in certain cases special operations (such as
+decrementing a reference count, removing the object from a table, etc)
+must be performed. For such cases a user supplied
+release-function is needed.
+
The release-function is invoked at most once for any foreign
+object. After the release-function is invoked, the foreign
+object is considered “released” and can no longer be used in a
+foreign type conversion. When the garbage collector detects that a
+foreign object is no longer reachable by the program, it will invoke
+the release-function if the foreign object is not yet released.
+When there is a need to release the foreign object promptly, the
+program can explicitly call (foreign-release! obj) which
+invokes the release-function if the foreign object is not yet
+released, and does nothing otherwise. The call
+(foreign-released? obj) returns a boolean indicating
+whether the foreign object obj has been released yet or not.
+The call (foreign-address obj) returns the address
+denoted by the internal pointer of foreign object obj or 0 if it
+has been released. The call (foreign? obj) tests that
+obj is a foreign object. Finally the call (foreign-tags
+obj) returns the list of tags of foreign object obj, or
+#f.
+
The following table gives the C types to which each Scheme type +can be converted: +
+Allowed target C types +
#fscheme-object; bool;
+pointer;
+function;
+char-string;
+ISO-8859-1-string;
+UTF-8-string;
+UTF-16-string;
+UCS-2-string;
+UCS-4-string;
+wchar_t-string
+
#tscheme-object; bool
+
scheme-object; bool;
+[[un]signed] char; ISO-8859-1; UCS-2;
+UCS-4; wchar_t
+
scheme-object; bool; [unsigned-]
+int8/int16/int32/int64; [unsigned]
+short/int/long
+
scheme-object; bool; float; double; float32; float64
+
scheme-object; bool;
+char-string;
+nonnull-char-string;
+ISO-8859-1-string;
+nonnull-ISO-8859-1-string;
+UTF-8-string;
+nonnull-UTF-8-string;
+UTF-16-string;
+nonnull-UTF-16-string;
+UCS-2-string;
+nonnull-UCS-2-string;
+UCS-4-string;
+nonnull-UCS-4-string;
+wchar_t-string;
+nonnull-wchar_t-string
+
scheme-object; bool; struct/union/type/pointer/nonnull-pointer with the appropriate tags
+
scheme-object; bool
+
scheme-object; bool
+
scheme-object; bool;
+function;
+nonnull-function
+
scheme-object; bool
+
The following table gives the Scheme types to which each C type +will be converted: +
+Resulting Scheme type +
the Scheme object encoded +
boolean +
[un]signed] char; ISO-8859-1; UCS-2; UCS-4; wchar_tcharacter +
unsigned-] int8/int16/int32/int64; [unsigned] short/int/longexact integer +
float; double; float32; float64inexact real +
char-string; ISO-8859-1-string; UTF-8-string; UTF-16-string; UCS-2-string; UCS-4-string; wchar_t-stringstring or #f if it is equal to NULL
+
nonnull-char-string; nonnull-ISO-8859-1-string; nonnull-UTF-8-string; nonnull-UTF-16-string; nonnull-UCS-2-string; nonnull-UCS-4-string; nonnull-wchar_t-stringstring +
struct/union/type/pointer/nonnull-pointerforeign object with the appropriate tags
+or #f in the case of a pointer equal to NULL
+
functionprocedure or #f if it is equal to NULL
+
nonnull-functionprocedure +
voidvoid object +
All Scheme types are compatible with the C types scheme-object
+and bool. Conversion to and from the C type
+scheme-object is the identity function on the object encoding.
+This provides a low-level mechanism for accessing Scheme’s object
+representation from C (with the help of the macros in the
+gambit.h header file). When a C bool type is expected,
+an extended Scheme boolean can be passed (#f is converted to 0
+and all other values are converted to 1).
+
The Scheme boolean #f can be passed to the C environment where
+a char-string, ISO-8859-1-string, UTF-8-string,
+UTF-16-string, UCS-2-string, UCS-4-string,
+wchar_t-string, pointer or function type is
+expected. In this case, #f is converted to the NULL
+pointer. C bools are extended booleans so any value different
+from 0 represents true. Thus, a C bool passed to the Scheme
+environment is mapped as follows: 0 to #f and all other values
+to #t.
+
A Scheme character passed to the C environment where any C character +type is expected is converted to the corresponding character in the C +environment. An error is signaled if the Scheme character does not fit +in the C character. Any C character type passed to Scheme is converted +to the corresponding Scheme character. An error is signaled if the C +character does not fit in the Scheme character. +
+A Scheme exact integer passed to the C environment where a C integer
+type (other than char) is expected is converted to the
+corresponding integral value. An error is signaled if the value falls
+outside of the range representable by that integral type. C integer
+values passed to the Scheme environment are mapped to the same Scheme
+exact integer. If the value is outside the fixnum range, a bignum is
+created.
+
A Scheme inexact real passed to the C environment is converted to the
+corresponding float, double, float32 or
+float64 value. C float, double, float32 and
+float64 values passed to the Scheme environment are mapped to the
+closest Scheme inexact real.
+
Scheme’s rational numbers and complex numbers are not compatible with +any C numeric type. +
+A Scheme string passed to the C environment where any C string type is
+expected is converted to a null terminated string using the appropriate
+encoding. The C string is a fresh copy of the Scheme string. If the C
+string was created for an argument of a c-lambda, the C string
+will be reclaimed when the c-lambda returns. If the C string was
+created for returning the result of a c-define to C, the caller
+is responsible for reclaiming the C string with a call to the
+___release_string function (see below for an example). Any C
+string type passed to the Scheme environment causes the creation of a
+fresh Scheme string containing a copy of the C string (unless the C
+string is equal to NULL, in which case it is converted to
+#f).
+
A foreign type passed to the Scheme environment causes the creation
+and initialization of a Scheme foreign object with the appropriate
+tags (except for the case of a pointer equal to NULL
+which is converted to #f). A Scheme foreign object can be
+passed where a foreign type is expected, on the condition that the
+tags are compatible and the Scheme foreign object is not yet released.
+The value #f is also acceptable for a pointer type, and
+is converted to NULL.
+
Scheme procedures defined with the c-define special form can be
+passed where the function and nonnull-function types are
+expected. The value #f is also acceptable for a function
+type, and is converted to NULL. No other Scheme procedures are
+acceptable. Conversion from the function and
+nonnull-function types to Scheme procedures is not currently
+implemented.
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
c-declare special form (c-declare c-declaration) | special form |
Initially, the C file produced by gsc contains only an
+#include of gambit.h. This header file provides a
+number of macro and procedure declarations to access the Scheme object
+representation. The special form c-declare adds
+c-declaration (which must be a string containing the C
+declarations) to the C file. This string is copied to the C file on a
+new line so it can start with preprocessor directives. All types of C
+declarations are allowed (including type declarations, variable
+declarations, function declarations, #include directives,
+#defines, and so on). These declarations are visible to
+subsequent c-declares, c-initializes, and
+c-lambdas, and c-defines in the same module. The most
+common use of this special form is to declare the external functions
+that are referenced in c-lambda special forms. Such functions
+must either be declared explicitly or by including a header file which
+contains the appropriate C declarations.
+
The c-declare special form does not return a value.
+It can only appear at top level.
+
For example: +
+(c-declare #<<c-declare-end + +#include <stdio.h> + +extern char *getlogin (); + +#ifdef sparc +char *host = "sparc"; +#else +char *host = "unknown"; +#endif + +FILE *tfile; + +c-declare-end +) + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
c-initialize special form (c-initialize c-code) | special form |
Just after the program is loaded and before control is passed to the
+Scheme code, each C file is initialized by calling its associated
+initialization function. The body of this function is normally empty
+but it can be extended by using the c-initialize form. Each
+occurence of the c-initialize form adds code to the body of the
+initialization function in the order of appearance in the source file.
+c-code must be a string containing the C code to execute. This
+string is copied to the C file on a new line so it can start with
+preprocessor directives.
+
The c-initialize special form does not return a value.
+It can only appear at top level.
+
For example: +
+(c-initialize "tfile = tmpfile ();") + |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
c-lambda special form (c-lambda (type1…) result-type c-name-or-code) | special form |
The c-lambda special form makes it possible to create a Scheme
+procedure that will act as a representative of some C function or C code
+sequence. The first subform is a list containing the type of each
+argument. The type of the function’s result is given next. Finally,
+the last subform is a string that either contains the name of the C
+function to call or some sequence of C code to execute. Variadic C
+functions are not supported. The resulting Scheme procedure takes
+exactly the number of arguments specified and delivers them in the same
+order to the C function. When the Scheme procedure is called, the
+arguments will be converted to their C representation and then the C
+function will be called. The result returned by the C function will be
+converted to its Scheme representation and this value will be returned
+from the Scheme procedure call. An error will be signaled if some
+conversion is not possible. The temporary memory allocated from the C
+heap for the conversion of the arguments and result will be reclaimed
+whether there is an error or not.
+
When c-name-or-code is not a valid C identifier, it is treated
+as an arbitrary piece of C code. Within the C code the variables
+___arg1, ___arg2, etc. can be referenced to access the
+converted arguments. Similarly, the result to be returned from the
+call should be assigned to the variable ___result except when
+the result is of type struct, union, type,
+pointer, nonnull-pointer, function or
+nonnull-function in which case a pointer must be assigned to
+the variable ___result_voidstar which is of type void*.
+For results of type pointer, nonnull-pointer,
+function and nonnull-function, the value assigned to the
+variable ___result_voidstar must be the pointer or function
+cast to void*. For results of type struct,
+union, and type, the value assigned to the variable
+___result_voidstar must be a pointer to a memory allocated
+block containing a copy of the result. Note that this block will be
+reclaimed by the release-function associated with the type.
+If no result needs to be returned, the result-type should be
+void and no assignment to the variable ___result or
+___result_voidstar should take place. Note that the C code
+should not contain return statements as this is meaningless.
+Control must always fall off the end of the C code. The C code is
+copied to the C file on a new line so it can start with preprocessor
+directives. Moreover the C code is always placed at the head of a
+compound statement whose lifetime encloses the C to Scheme conversion of
+the result. Consequently, temporary storage (strings in particular)
+declared at the head of the C code can be returned by assigning them to
+___result or ___result_voidstar. In the
+c-name-or-code, the macro ___AT_END may be defined as the
+piece of C code to execute before control is returned to Scheme but
+after the result is converted to its Scheme representation. This is
+mainly useful to deallocate temporary storage contained in the result.
+
When passed to the Scheme environment, the C void type is
+converted to the void object.
+
For example: +
+(define fopen
+ (c-lambda (nonnull-char-string nonnull-char-string)
+ (pointer "FILE")
+ "fopen"))
+
+(define fgetc
+ (c-lambda ((pointer "FILE"))
+ int
+ "fgetc"))
+
+(let ((f (fopen "datafile" "r")))
+ (if f (write (fgetc f))))
+
+(define char-code
+ (c-lambda (char) int "___result = ___arg1;"))
+
+(define host
+ ((c-lambda () nonnull-char-string "___result = host;")))
+
+(define stdin
+ ((c-lambda () (pointer "FILE") "___result_voidstar = stdin;")))
+
+((c-lambda () void
+#<<c-lambda-end
+ printf( "hello\n" );
+ printf( "world\n" );
+c-lambda-end
+))
+
+(define pack-1-char
+ (c-lambda (char)
+ nonnull-char-string
+#<<c-lambda-end
+ ___result = malloc (2);
+ if (___result != NULL) { ___result[0] = ___arg1; ___result[1] = 0; }
+ #define ___AT_END if (___result != NULL) free (___result);
+c-lambda-end
+))
+
+(define pack-2-chars
+ (c-lambda (char char)
+ nonnull-char-string
+#<<c-lambda-end
+ char s[3];
+ s[0] = ___arg1;
+ s[1] = ___arg2;
+ s[2] = 0;
+ ___result = s;
+c-lambda-end
+))
+ |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
c-define special form (c-define (variable define-formals) (type1…) result-type c-name scope body) | special form |
The c-define special form makes it possible to create a C
+function that will act as a representative of some Scheme procedure. A
+C function named c-name as well as a Scheme procedure bound to the
+variable variable are defined. The parameters of the Scheme
+procedure are define-formals and its body is at the end of the
+form. The type of each argument of the C function, its result type and
+c-name (which must be a string) are specified after the parameter
+specification of the Scheme procedure. When the C function c-name
+is called from C, its arguments are converted to their Scheme
+representation and passed to the Scheme procedure. The result of the
+Scheme procedure is then converted to its C representation and the C
+function c-name returns it to its caller.
+
The scope of the C function can be changed with the scope
+parameter, which must be a string. This string is placed immediately
+before the declaration of the C function. So if scope is the
+string "static", the scope of c-name is local to the module
+it is in, whereas if scope is the empty string, c-name is
+visible from other modules.
+
The c-define special form does not return a value.
+It can only appear at top level.
+
For example: +
+(c-define (proc x #!optional (y x) #!rest z) (int int char float) int "f" "" + (write (cons x (cons y z))) + (newline) + (+ x y)) + +(proc 1 2 #\x 1.5) => 3 and prints (1 2 #\x 1.5) +(proc 1) => 2 and prints (1 1) + +; if f is called from C with the call f (1, 2, 'x', 1.5) +; the value 3 is returned and (1 2 #\x 1.5) is printed. +; f has to be called with 4 arguments. + |
The c-define special form is particularly useful when the
+driving part of an application is written in C and Scheme procedures
+are called directly from C. The Scheme part of the application is in
+a sense a “server” that is providing services to the C part. The
+Scheme procedures that are to be called from C need to be defined
+using the c-define special form. Before it can be used, the
+Scheme part must be initialized with a call to the function
+___setup. Before the program terminates, it must call the
+function ___cleanup so that the Scheme part may do final
+cleanup. A sample application is given in the file
+tests/server.scm.
+
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
c-define-type special form (c-define-type name type [c-to-scheme scheme-to-c [cleanup]]) | special form |
This form associates the type identifier name to the C type
+type. The name must not clash with predefined types
+(e.g. char-string, ISO-8859-1, etc.) or with types previously
+defined with c-define-type in the same file. The
+c-define-type special form does not return a value. It can only
+appear at top level.
+
If only the two parameters name and type are supplied then +after this definition, the use of name in a type specification is +synonymous to type. +
+For example: +
+(c-define-type FILE "FILE") +(c-define-type FILE* (pointer FILE)) +(c-define-type time-struct-ptr (pointer (struct "tms"))) +(define fopen (c-lambda (char-string char-string) FILE* "fopen")) +(define fgetc (c-lambda (FILE*) int "fgetc")) + |
Note that identifiers are not case-sensitive in standard Scheme but it +is good programming practice to use a name with the same case as +in C. +
+If four or more parameters are supplied, then type must be a
+string naming the C type, c-to-scheme and scheme-to-c must
+be strings suffixing the C macros that convert data of that type between
+C and Scheme. If cleanup is supplied it must be a boolean
+indicating whether it is necessary to perform a cleanup operation (such
+as freeing memory) when data of that type is converted from Scheme to C
+(it defaults to #t). The cleanup information is used when the C
+stack is unwound due to a continuation invocation (see
+Continuations and the C-interface). Although it is safe to always specify #t,
+it is more efficient in time and space to specify #f because the
+unwinding mechanism can skip C-interface frames which only contain
+conversions of data types requiring no cleanup. Two pairs of C macros
+need to be defined for conversions performed by c-lambda forms
+and two pairs for conversions performed by c-define forms:
+
___BEGIN_CFUN_scheme-to-c(___SCMOBJ, type, int) +___END_CFUN_scheme-to-c(___SCMOBJ, type, int) + +___BEGIN_CFUN_c-to-scheme(type, ___SCMOBJ) +___END_CFUN_c-to-scheme(type, ___SCMOBJ) + +___BEGIN_SFUN_c-to-scheme(type, ___SCMOBJ, int) +___END_SFUN_c-to-scheme(type, ___SCMOBJ, int) + +___BEGIN_SFUN_scheme-to-c(___SCMOBJ, type) +___END_SFUN_scheme-to-c(___SCMOBJ, type) + |
The macros prefixed with ___BEGIN perform the conversion and
+those prefixed with ___END perform any cleanup necessary (such as
+freeing memory temporarily allocated for the conversion). The macro
+___END_CFUN_scheme-to-c must free the result of the
+conversion if it is memory allocated, and
+___END_SFUN_scheme-to-c must not (i.e. it is the
+responsibility of the caller to free the result).
+
The first parameter of these macros is the C variable that contains the
+value to be converted, and the second parameter is the C variable in
+which to store the converted value. The third parameter, when present,
+is the index (starting at 1) of the parameter of the c-lambda or
+c-define form that is being converted (this is useful for
+reporting precise error information when a conversion is impossible).
+
To allow for type checking, the first three ___BEGIN macros must
+expand to an unterminated compound statement prefixed by an if,
+conditional on the absence of type check error:
+
if ((___err = conversion_operation) == ___FIX(___NO_ERR)) {
+ |
The last ___BEGIN macro must expand to an unterminated compound
+statement:
+
{ ___err = conversion_operation;
+ |
If type check errors are impossible then a ___BEGIN macro can
+simply expand to an unterminated compound statement performing the
+conversion:
+
{ conversion_operation;
+ |
The ___END macros must expand to a statement, or to nothing if no
+cleanup is required, followed by a closing brace (to terminate the
+compound statement started at the corresponding ___BEGIN macro).
+
The conversion_operation is typically a function call that returns
+an error code value of type ___SCMOBJ (the error codes are defined in
+gambit.h, and the error code ___FIX(___UNKNOWN_ERR) is available
+for generic errors). conversion_operation can also set the
+variable ___errmsg of type ___SCMOBJ to a specific Scheme
+string error message.
+
Below is a simple example showing how to interface to an EBCDIC +character type. Memory allocation is not needed for conversion and type +check errors are impossible when converting EBCDIC to Scheme characters, +but they are possible when converting from Scheme characters to EBCDIC +since Gambit supports Unicode characters. +
+(c-declare #<<c-declare-end
+
+typedef char EBCDIC; /* EBCDIC encoded characters */
+
+void put_char (EBCDIC c) { ... } /* EBCDIC I/O functions */
+EBCDIC get_char (void) { ... }
+
+char EBCDIC_to_ISO_8859_1[256] = { ... }; /* conversion tables */
+char ISO_8859_1_to_EBCDIC[256] = { ... };
+
+___SCMOBJ SCMOBJ_to_EBCDIC (___SCMOBJ src, EBCDIC *dst)
+{
+ int x = ___INT(src); /* convert from Scheme character to int */
+ if (x > 255) return ___FIX(___UNKNOWN_ERR);
+ *dst = ISO_8859_1_to_EBCDIC[x];
+ return ___FIX(___NO_ERR);
+}
+
+#define ___BEGIN_CFUN_SCMOBJ_to_EBCDIC(src,dst,i) \
+if ((___err = SCMOBJ_to_EBCDIC (src, &dst)) == ___FIX(___NO_ERR)) {
+#define ___END_CFUN_SCMOBJ_to_EBCDIC(src,dst,i) }
+
+#define ___BEGIN_CFUN_EBCDIC_to_SCMOBJ(src,dst) \
+{ dst = ___CHR(EBCDIC_to_ISO_8859_1[src]);
+#define ___END_CFUN_EBCDIC_to_SCMOBJ(src,dst) }
+
+#define ___BEGIN_SFUN_EBCDIC_to_SCMOBJ(src,dst,i) \
+{ dst = ___CHR(EBCDIC_to_ISO_8859_1[src]);
+#define ___END_SFUN_EBCDIC_to_SCMOBJ(src,dst,i) }
+
+#define ___BEGIN_SFUN_SCMOBJ_to_EBCDIC(src,dst) \
+{ ___err = SCMOBJ_to_EBCDIC (src, &dst);
+#define ___END_SFUN_SCMOBJ_to_EBCDIC(src,dst) }
+
+c-declare-end
+)
+
+(c-define-type EBCDIC "EBCDIC" "EBCDIC_to_SCMOBJ" "SCMOBJ_to_EBCDIC" #f)
+
+(define put-char (c-lambda (EBCDIC) void "put_char"))
+(define get-char (c-lambda () EBCDIC "get_char"))
+
+(c-define (write-EBCDIC c) (EBCDIC) void "write_EBCDIC" ""
+ (write-char c))
+
+(c-define (read-EBCDIC) () EBCDIC "read_EBCDIC" ""
+ (read-char))
+ |
Below is a more complex example that requires memory allocation when
+converting from C to Scheme. It is an interface to a 2D point
+type which is represented in Scheme by a pair of integers. The
+conversion of the x and y components is done by calls to
+the conversion macros for the int type (defined in
+gambit.h). Note that no cleanup is necessary when converting
+from Scheme to C (i.e. the last parameter of the c-define-type is
+#f).
+
(c-declare #<<c-declare-end
+
+typedef struct { int x, y; } point;
+
+void line_to (point p) { ... }
+point get_mouse (void) { ... }
+point add_points (point p1, point p2) { ... }
+
+___SCMOBJ SCMOBJ_to_POINT (___SCMOBJ src, point *dst, int arg_num)
+{
+ ___SCMOBJ ___err = ___FIX(___NO_ERR);
+ if (!___PAIRP(src))
+ ___err = ___FIX(___UNKNOWN_ERR);
+ else
+ {
+ ___SCMOBJ car = ___CAR(src);
+ ___SCMOBJ cdr = ___CDR(src);
+ ___BEGIN_CFUN_SCMOBJ_TO_INT(car,dst->x,arg_num)
+ ___BEGIN_CFUN_SCMOBJ_TO_INT(cdr,dst->y,arg_num)
+ ___END_CFUN_SCMOBJ_TO_INT(cdr,dst->y,arg_num)
+ ___END_CFUN_SCMOBJ_TO_INT(car,dst->x,arg_num)
+ }
+ return ___err;
+}
+
+___SCMOBJ POINT_to_SCMOBJ (point src, ___SCMOBJ *dst, int arg_num)
+{
+ ___SCMOBJ ___err = ___FIX(___NO_ERR);
+ ___SCMOBJ x_scmobj;
+ ___SCMOBJ y_scmobj;
+ ___BEGIN_SFUN_INT_TO_SCMOBJ(src.x,x_scmobj,arg_num)
+ ___BEGIN_SFUN_INT_TO_SCMOBJ(src.y,y_scmobj,arg_num)
+ *dst = ___EXT(___make_pair) (x_scmobj, y_scmobj, ___STILL);
+ if (___FIXNUMP(*dst))
+ ___err = *dst; /* return allocation error */
+ ___END_SFUN_INT_TO_SCMOBJ(src.y,y_scmobj,arg_num)
+ ___END_SFUN_INT_TO_SCMOBJ(src.x,x_scmobj,arg_num)
+ return ___err;
+}
+
+#define ___BEGIN_CFUN_SCMOBJ_to_POINT(src,dst,i) \
+if ((___err = SCMOBJ_to_POINT (src, &dst, i)) == ___FIX(___NO_ERR)) {
+#define ___END_CFUN_SCMOBJ_to_POINT(src,dst,i) }
+
+#define ___BEGIN_CFUN_POINT_to_SCMOBJ(src,dst) \
+if ((___err = POINT_to_SCMOBJ (src, &dst, ___RETURN_POS)) == ___FIX(___NO_ERR)) {
+#define ___END_CFUN_POINT_to_SCMOBJ(src,dst) \
+___EXT(___release_scmobj) (dst); }
+
+#define ___BEGIN_SFUN_POINT_to_SCMOBJ(src,dst,i) \
+if ((___err = POINT_to_SCMOBJ (src, &dst, i)) == ___FIX(___NO_ERR)) {
+#define ___END_SFUN_POINT_to_SCMOBJ(src,dst,i) \
+___EXT(___release_scmobj) (dst); }
+
+#define ___BEGIN_SFUN_SCMOBJ_to_POINT(src,dst) \
+{ ___err = SCMOBJ_to_POINT (src, &dst, ___RETURN_POS);
+#define ___END_SFUN_SCMOBJ_to_POINT(src,dst) }
+
+c-declare-end
+)
+
+(c-define-type point "point" "POINT_to_SCMOBJ" "SCMOBJ_to_POINT" #f)
+
+(define line-to (c-lambda (point) void "line_to"))
+(define get-mouse (c-lambda () point "get_mouse"))
+(define add-points (c-lambda (point point) point "add_points"))
+
+(c-define (write-point p) (point) void "write_point" ""
+ (write p))
+
+(c-define (read-point) () point "read_point" ""
+ (read))
+ |
An example that requires memory allocation when converting from C to +Scheme and Scheme to C is shown below. It is an interface to a +“null-terminated array of strings” type which is represented in Scheme +by a list of strings. Note that some cleanup is necessary when +converting from Scheme to C. +
+(c-declare #<<c-declare-end
+
+#include <stdlib.h>
+#include <unistd.h>
+
+extern char **environ;
+
+char **get_environ (void) { return environ; }
+
+void free_strings (char **strings)
+{
+ char **ptr = strings;
+ while (*ptr != NULL)
+ {
+ ___EXT(___release_string) (*ptr);
+ ptr++;
+ }
+ free (strings);
+}
+
+___SCMOBJ SCMOBJ_to_STRINGS (___SCMOBJ src, char ***dst, int arg_num)
+{
+ /*
+ * Src is a list of Scheme strings. Dst will be a null terminated
+ * array of C strings.
+ */
+
+ int i;
+ ___SCMOBJ lst = src;
+ int len = 4; /* start with a small result array */
+ char **result = (char**) malloc (len * sizeof (char*));
+
+ if (result == NULL)
+ return ___FIX(___HEAP_OVERFLOW_ERR);
+
+ i = 0;
+ result[i] = NULL; /* always keep array null terminated */
+
+ while (___PAIRP(lst))
+ {
+ ___SCMOBJ scm_str = ___CAR(lst);
+ char *c_str;
+ ___SCMOBJ ___err;
+
+ if (i >= len-1) /* need to grow the result array? */
+ {
+ char **new_result;
+ int j;
+
+ len = len * 3 / 2;
+ new_result = (char**) malloc (len * sizeof (char*));
+ if (new_result == NULL)
+ {
+ free_strings (result);
+ return ___FIX(___HEAP_OVERFLOW_ERR);
+ }
+ for (j=i; j>=0; j--)
+ new_result[j] = result[j];
+ free (result);
+ result = new_result;
+ }
+
+ ___err = ___EXT(___SCMOBJ_to_CHARSTRING) (scm_str, &c_str, arg_num);
+
+ if (___err != ___FIX(___NO_ERR))
+ {
+ free_strings (result);
+ return ___err;
+ }
+
+ result[i++] = c_str;
+ result[i] = NULL;
+ lst = ___CDR(lst);
+ }
+
+ if (!___NULLP(lst))
+ {
+ free_strings (result);
+ return ___FIX(___UNKNOWN_ERR);
+ }
+
+ /*
+ * Note that the caller is responsible for calling free_strings
+ * when it is done with the result.
+ */
+
+ *dst = result;
+ return ___FIX(___NO_ERR);
+}
+
+___SCMOBJ STRINGS_to_SCMOBJ (char **src, ___SCMOBJ *dst, int arg_num)
+{
+ ___SCMOBJ ___err = ___FIX(___NO_ERR);
+ ___SCMOBJ result = ___NUL; /* start with the empty list */
+ int i = 0;
+
+ while (src[i] != NULL)
+ i++;
+
+ /* build the list of strings starting at the tail */
+
+ while (--i >= 0)
+ {
+ ___SCMOBJ scm_str;
+ ___SCMOBJ new_result;
+
+ /*
+ * Invariant: result is either the empty list or a ___STILL pair
+ * with reference count equal to 1. This is important because
+ * it is possible that ___CHARSTRING_to_SCMOBJ and ___make_pair
+ * will invoke the garbage collector and we don't want the
+ * reference in result to become invalid (which would be the
+ * case if result was a ___MOVABLE pair or if it had a zero
+ * reference count).
+ */
+
+ ___err = ___EXT(___CHARSTRING_to_SCMOBJ) (src[i], &scm_str, arg_num);
+
+ if (___err != ___FIX(___NO_ERR))
+ {
+ ___EXT(___release_scmobj) (result); /* allow GC to reclaim result */
+ return ___FIX(___UNKNOWN_ERR);
+ }
+
+ /*
+ * Note that scm_str will be a ___STILL object with reference
+ * count equal to 1, so there is no risk that it will be
+ * reclaimed or moved if ___make_pair invokes the garbage
+ * collector.
+ */
+
+ new_result = ___EXT(___make_pair) (scm_str, result, ___STILL);
+
+ /*
+ * We can zero the reference count of scm_str and result (if
+ * not the empty list) because the pair now references these
+ * objects and the pair is reachable (it can't be reclaimed
+ * or moved by the garbage collector).
+ */
+
+ ___EXT(___release_scmobj) (scm_str);
+ ___EXT(___release_scmobj) (result);
+
+ result = new_result;
+
+ if (___FIXNUMP(result))
+ return result; /* allocation failed */
+ }
+
+ /*
+ * Note that result is either the empty list or a ___STILL pair
+ * with a reference count equal to 1. There will be a call to
+ * ___release_scmobj later on (in ___END_CFUN_STRINGS_to_SCMOBJ
+ * or ___END_SFUN_STRINGS_to_SCMOBJ) that will allow the garbage
+ * collector to reclaim the whole list of strings when the Scheme
+ * world no longer references it.
+ */
+
+ *dst = result;
+ return ___FIX(___NO_ERR);
+}
+
+#define ___BEGIN_CFUN_SCMOBJ_to_STRINGS(src,dst,i) \
+if ((___err = SCMOBJ_to_STRINGS (src, &dst, i)) == ___FIX(___NO_ERR)) {
+#define ___END_CFUN_SCMOBJ_to_STRINGS(src,dst,i) \
+free_strings (dst); }
+
+#define ___BEGIN_CFUN_STRINGS_to_SCMOBJ(src,dst) \
+if ((___err = STRINGS_to_SCMOBJ (src, &dst, ___RETURN_POS)) == ___FIX(___NO_ERR)) {
+#define ___END_CFUN_STRINGS_to_SCMOBJ(src,dst) \
+___EXT(___release_scmobj) (dst); }
+
+#define ___BEGIN_SFUN_STRINGS_to_SCMOBJ(src,dst,i) \
+if ((___err = STRINGS_to_SCMOBJ (src, &dst, i)) == ___FIX(___NO_ERR)) {
+#define ___END_SFUN_STRINGS_to_SCMOBJ(src,dst,i) \
+___EXT(___release_scmobj) (dst); }
+
+#define ___BEGIN_SFUN_SCMOBJ_to_STRINGS(src,dst) \
+{ ___err = SCMOBJ_to_STRINGS (src, &dst, ___RETURN_POS);
+#define ___END_SFUN_SCMOBJ_to_STRINGS(src,dst) }
+
+c-declare-end
+)
+
+(c-define-type char** "char**" "STRINGS_to_SCMOBJ" "SCMOBJ_to_STRINGS")
+
+(define execv (c-lambda (char-string char**) int "execv"))
+(define get-environ (c-lambda () char** "get_environ"))
+
+(c-define (write-strings x) (char**) void "write_strings" ""
+ (write x))
+
+(c-define (read-strings) () char** "read_strings" ""
+ (read))
+ |
|
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The C-interface allows C to Scheme calls to be nested. This means +that during a call from C to Scheme another call from C to Scheme +can be performed. This case occurs in the following program: +
+(c-declare #<<c-declare-end
+
+int p (char *); /* forward declarations */
+int q (void);
+
+int a (char *x) { return 2 * p (x+1); }
+int b (short y) { return y + q (); }
+
+c-declare-end
+)
+
+(define a (c-lambda (char-string) int "a"))
+(define b (c-lambda (short) int "b"))
+
+(c-define (p z) (char-string) int "p" ""
+ (+ (b 10) (string-length z)))
+
+(c-define (q) () int "q" ""
+ 123)
+
+(write (a "hello"))
+ |
In this example, the main Scheme program calls the C function a +which calls the Scheme procedure p which in turn calls the C +function b which finally calls the Scheme procedure q. +
+Gambit-C maintains the Scheme continuation separately from the C stack, +thus allowing the Scheme continuation to be unwound independently from +the C stack. The C stack frame created for the C function f is +only removed from the C stack when control returns from f or when +control returns to a C function “above” f. Special care is +required for programs which escape to Scheme (using first-class +continuations) from a Scheme to C (to Scheme) call because the C stack +frame will remain on the stack. The C stack may overflow if this +happens in a loop with no intervening return to a C function. To avoid +this problem make sure the C stack gets cleaned up by executing a normal +return from a Scheme to C call. +
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
define) of the same procedure. Replace all
+but the first define with assignments (set!).
+
+apply procedure is 8192.
+
+ |
+ |
++ | |
+ |
+ |
+ |
+ |
+ |
+
The Gambit-C system release v4.6.1 is Copyright © +1994-2009 by Marc Feeley, all rights reserved. The Gambit-C system +release v4.6.1 is licensed under two licenses: the Apache +License, Version 2.0, and the GNU LESSER GENERAL PUBLIC LICENSE, +Version 2.1. You have the option to choose which of these two +licenses to abide by. The licenses are copied below. +
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#! syntax+Gambit REPL is an interpreter for the Scheme programming language which closely conforms to the Scheme standard and also provides a large number of extensions. The following documents define the R5RS Scheme language and the extensions specific to the Gambit system, on which Gambit REPL is based. +
+ + + + + ++Gambit REPL's user interface provides 4 views which are selectable with the tabs at the bottom of the screen. The views can be switched from portrait to landscape by turning the device. The landscape layout is recommended on iPhone, as it gives a keyboard with wider keys and text output with fewer line breaks. +
+ ++The following predefined procedures are specific to Gambit REPL. +
+ +(splash)(repl)(repl-eval input)(repl-eval "(+ 1 2)\n").
+
+(wiki)(help)help procedure can also be called with a subject argument to open the appropriate section of the HTML documentation, for example (help help) gives the documentation of the help procedure.
+
+(edit)(open-URL string)(open-URL "http://www.apple.com").
+
+(reset-scripts)(repl-server password)telnet 192.168.0.100 7000+The Scheme file I/O procedures will read and write files in an area specific to the Gambit REPL app. The path "~" refers to the Documents folder. It is a convenient place to store files. This folder is initially empty. The content of the folder will be preserved when you update Gambit REPL to a newer version. The path "~~" refers to the Gambit REPL app bundle. +
+ + + + diff --git a/examples/iOS/html.scm b/examples/iOS/html.scm index 60f431eab..38f3aa384 100644 --- a/examples/iOS/html.scm +++ b/examples/iOS/html.scm @@ -319,12 +319,13 @@ port) (loop (+ end 1) (+ end 1)))))) (else + #; (display (string-append "Warning: Character (integer->char " (number->string index) ") is not a valid HTML 4.0 character entity\n") - (current-error-port)) + (repl-output-port)) (loop start (+ end 1))))))))))) ) diff --git a/examples/iOS/intf#.scm b/examples/iOS/intf#.scm new file mode 100644 index 000000000..2f6121aea --- /dev/null +++ b/examples/iOS/intf#.scm @@ -0,0 +1,115 @@ +;;;============================================================================ + +;;; File: "intf#.scm" + +;;; Copyright (c) 2011 by Marc Feeley, All Rights Reserved. + +;;;============================================================================ + +(##namespace ("intf#" + +string->Class +Class->string +string->SEL +SEL->string +send0 +send1 +send2 +id->string +string->id +id->bool +bool->id +id->int +int->id +id->float +float->id +id->double +double->id + +NSDate +alloc +init +description +date + +NSBundle +mainBundle +objectForInfoDictionaryKey +mainBundle-info +CFBundleName +CFBundleDisplayName + +currentDevice-batteryLevel +currentDevice-batteryMonitoringEnabled +currentDevice-batteryMonitoringEnabled-set! +currentDevice-multitaskingSupported +currentDevice-model +currentDevice-name +currentDevice-systemName +currentDevice-systemVersion +currentDevice-uniqueIdentifier +device-status +device-model +UDID + +AudioServicesPlayAlertSound +AudioServicesPlaySystemSound +kSystemSoundID_FlashScreen +kSystemSoundID_Vibrate +kSystemSoundID_UserPreferredAlert + +set-navigation +show-cancelButton +hide-cancelButton +show-textView +show-webView +set-textView-font +set-textView-content +get-textView-content +add-output-to-textView +add-input-to-textView +set-webView-content +set-webView-content-from-file +eval-js-in-webView + +open-URL +segm-ctrl-set-title +segm-ctrl-insert +set-pref +get-pref +set-pasteboard +get-pasteboard +popup-alert + +send-input +send-event +send-key +handle-key +heartbeat +next-heartbeat-interval +interval-runnable +interval-io-pending +interval-no-io-pending +interval-min-wait + +eval-string + +repl-port +event-port +event-handler + +set-event-handler +show-view +set-view-content +set-page +set-page-content + +has-prefix? +get-event-parameters + +contained-path-resolve +app-dir + +)) + +;;;============================================================================ diff --git a/examples/iOS/intf.h b/examples/iOS/intf.h new file mode 100644 index 000000000..b7cdaccea --- /dev/null +++ b/examples/iOS/intf.h @@ -0,0 +1,16 @@ +/* File: "intf.h" */ + +/* + * Scheme functions which can be called from C. These functions are + * declared with a c-define in "intf.scm". + */ + +extern NSString *eval_string(NSString *); + +extern void send_input(NSString *); + +extern void send_event(NSString *); + +extern void send_key(NSString *); + +extern double heartbeat(); diff --git a/examples/iOS/intf.scm b/examples/iOS/intf.scm new file mode 100644 index 000000000..7cc0e54e0 --- /dev/null +++ b/examples/iOS/intf.scm @@ -0,0 +1,681 @@ +;;;============================================================================ + +;;; File: "intf.scm" + +;;; Copyright (c) 2011 by Marc Feeley, All Rights Reserved. + +;;;============================================================================ + +(##namespace ("intf#")) + +(##include "~~lib/gambit#.scm") +(##include "~~lib/_gambit#.scm") + +(##include "intf#.scm") +(##include "url#.scm") + +(declare + (standard-bindings) + (extended-bindings) + (block) + (fixnum) + ;;(not safe) +) + + +;;;============================================================================ + +;; Interface with Objective-C. + +(c-declare #<
Welcome to
splash-page-content-part1-end
)
(define splash-page-content-part2 #<
-After the ">" prompt enter your command then RETURN and the REPL will display the result. Here is a sample interaction:
-
> prompt, then tap return to display the result. Here is a sample interaction:
+
> (+ 1 (/ (* 2 2) (sqrt 9)))
7/3
> (expt 2 100)
@@ -1024,275 +302,120 @@ After the ">" prompt enter your command then RE
1
4
9
-> (exit)
+
-