Walrus.md

What we need to implement an R7RS runtime over R6RS

Lexical syntax

• Support #u8 rather than #vu8
• Support datum labels (#n= and #n#)
• Support #true and #false
• Vertical-bar escapes around symbols

Syntax (and associated procedures)

• Support include syntax with the (include) library
• Support cond-expand syntax (somehow)
• Support delay-force syntax and promise? and make-promise procedure (may need to reimplement promises)
• Support SRFI 39 parameters (Chez's parameters aren't compatible)
• Add support for (... <template>), which removes the special meaning of ellipsis
• syntax-error needs to supply a who argument
• Support define-values syntax
• Translate R7RS define-record-type to R6RS define-record-type; the hard part is the constructor.

Libraries

• Reshape define-library forms into library forms with the help of the include library

Equivalence predicates

• Location tags for procedures (used by eq?)

Numbers

• finite? is true of non-real numbers if both the real and the imaginary parts are finite

• infinite? is true of non-real numbers if either the real or the imaginary parts or both are non-finite

• nan? is true of non-real numbers if either the real or the imaginary parts or both are NaN

• Define floor/, floor-quotient, floor-remainder, truncate/, truncate-quotient, truncate-remainderin terms ofdivandmod`: see r6rs-lib Chapter 19

• Define rationalize per IEEE 1178

Pairs and lists

• Define make-list
• Define list-ref
• Define list-set!
• Define member in terms of member and memp
• Define assoc in terms of assoc and assp
• Define list-copy

Characters

• Define digit-value
• Accept \| string escape

Strings

• Define string-copy!
• Define string-fill!

Vectors

• Define vector->string and string->vector
• Define vector-copy and vector-copy!

Bytevectors

• bytevector-copy takes start and end optional arguments
• bytevector-copy! takes different arguments
• Define bytevector-append
• utf8->string and string->utf8 take start and end optional arguments

Exceptions

• error needs to supply a who argument
• error-object-message and error-object-irritants are condition-message and condition-irritants (with safety checks)

Environments and evaluation

• eval accepts definitions
• Define scheme-environment and null-environment based on (rnrs r5rs)

Input and output

• Define open-binary-input-file and open-binary-output-file using open-file-input-port and open-file-output-port
• Define input-port-open? and output-port-open? (using exceptions somehow)
• Define get-output-string using second value of open-string-output-port
• Define get-output-bytevector using second value of open-bytevector-output-port
• Define read-bytevector and write-bytevector
• Define read-bytevector! and write-bytevector!
• Define peek-char and peek-u8 using lookahead-char and lookahead-u8'
• Define read based on R7RS lexical syntax
• Define write-simple as write
• Define write-circular and write-shared
• Define load
• Define command-line, exit, get-environment-variable, get-environment-variables, current-second, current-jiffy, jiffies-per-second, features (not portable)