GitHub - jhswartz/mp: Macro Processing with Forth

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WHAT IS MP? 

  MP is a macro processor that evaluates delimited Forth source code
  encountered in a stream of input text.

  It has been implemented as a filter program, meaning that it reads
  text received via the standard input stream and writes text to the 
  standard output stream.


HOW DOES IT WORK?

  All characters available via the input stream are READ and stored
  in the INPUT buffer. The characters in the buffer are subjected to
  a PROCESS that consists of two alternating phases of operation:

  1. In the first phase, characters are written to the output stream
     until the INTRODUCER character is encountered, or until the end
     of the buffer is reached.

  2. In the second phase, all characters between the last INTRODUCER
     character encountered and the next TERMINATOR character (or the
     end of buffer) are passed off as a string of Forth source code
     to EVALUATE.


WHAT ARE THE DELIMITERS?

  INTRODUCER and TERMINATOR are VALUES (assigned ` by default) that
  may be reassigned any character value at any time:

    `CHAR [ TO INTRODUCER  CHAR ] TO TERMINATOR`


USE CASE: HTML TEMPLATE PROCESSOR

  $ cat examples/countdown.html 
  `
  CREATE ACTIONS  S" BRIBERY" 2,  S" EXTORTION" 2,
  : ACT           2 CELLS * ACTIONS + 2@ TYPE ;
  : COIN-FLIP     TIME&DATE 5 0 DO DROP LOOP 2 MOD ;
  : COUNT-DOWN    1- SWAP -DO I . 1 -LOOP ;
  `
  <!DOCTYPE html>
  <html>
    <head>
      <title>Countdown to Corruption!</title>
    </head>
    <body>
      `10 0 COUNT-DOWN COIN-FLIP ACT`
    </body>
  </html>

  $ mp < examples/countdown.html 
  
  <!DOCTYPE html>
  <html>
    <head>
      <title>Countdown to Corruption!</title>
    </head>
    <body>
      10 9 8 7 6 5 4 3 2 1 0 EXTORTION
    </body>
  </html>


USE CASE: ASSEMBLY MACRO PROCESSOR 

  $ cat examples/gasleak.fs 
  CREATE CALL-REGS  S" %ebx" 2,  S" %ecx" 2,  S" %edx" 2,
                    S" %esi" 2,  S" %edi" 2,  S" %ebp" 2,
  
  : CALL-REG?       2 CELLS * CALL-REGS + 2@ ;
  
  : MOV             ." movl $" TYPE ." , " TYPE ." ; " ;
  : SYSCALL         ." movl $" 0 U.R ." , %eax; int $0x80; " ;
  : SYSCALL/ARGS:   CREATE , ,
                    DOES> DUP @ 0 ?DO I CALL-REG? PARSE-NAME MOV LOOP
                          CELL+ @ SYSCALL ;
  
  1 1 SYSCALL/ARGS: SYS-EXIT
  4 3 SYSCALL/ARGS: SYS-WRITE

  $ cat examples/goodbye.s 
  `REQUIRE examples/gasleak.fs`
  
  .section .text
  .global _start
  _start:
  	`SYS-WRITE 1 msg msglen`
  	`SYS-EXIT 0`
  
  .section .data
  msg: .ascii "GOODBYE!\n"
  .set msglen, . - msg

  $ ./mp < examples/goodbye.s | as -o examples/goodbye.o
  $ objdump -d examples/goodbye.o

  goodbye.o:     file format elf32-i386
  
  
  Disassembly of section .text:
  
  00000000 <_start>:
     0:   bb 01 00 00 00          mov    $0x1,%ebx
     5:   b9 00 00 00 00          mov    $0x0,%ecx
     a:   ba 09 00 00 00          mov    $0x9,%edx
     f:   b8 04 00 00 00          mov    $0x4,%eax
    14:   cd 80                   int    $0x80
    16:   bb 00 00 00 00          mov    $0x0,%ebx
    1b:   b8 01 00 00 00          mov    $0x1,%eax
    20:   cd 80                   int    $0x80

  $ ld -o examples/goodbye examples/goodbye.o
  $ examples/goodbye 
  GOODBYE!


HOW DO I INSTALL IT?

  The "mp" wrapper and "Makefile" were written with gforth in mind.
  Alter these files to suit the needs of your system, if necessary.

  # make install
  install -m 644 mp.fs /usr/share/gforth/site-forth
  install -m 755 mp    /usr/local/bin