#* 

  A script to translate the "Brainf***" language into plain
  c. This version of the script uses a one to one compilation 
  of commands. so ++++ will be translated into 4 "c" statements,
  which is not efficient.

  * Valid brainf commands
  >> ">" p++ "<" p-- "+" *p++ - *p-- "[]" while *p > 0 . putchar , getchar


TESTING
  
  * translate a Brainf*** program to c, compile and execute
  ----
    pep -f ../brainf.toclang.pss -i '.,,,' > test.c; 
    gcc test.c -o test; ./test
  ,,,,f

NOTES

  Other things to think about, include array bounds checking, and 
  handling of EOF.

  This script demonstrates pep/nom parsing and translating one of 
  the simplest possible formal languages.

  The script could be greatly reduced but some error messages are printed with
  line and character number.

  Hardly any parsing is required, just for "[" and "]" I put a line:char number
  message into the attribute for each [ or ], and then use that message if the
  brackets are unbalanced.  This technique could be useful for other languages.
  This is because we dont need that tape-cell (token attribute) for anything
  else.

HISTORY

  30 july 2022
    Made the script generate compilable c code and tested 
    with some simple scripts. 
  14 july 2022
    wrote this script.
*#

  read;
  ">","<","+","-",",","." {
    ">" { clear; add "p++;"; }
    "<" { clear; add "p--;"; }
    "+" { 
      clear; 
      # do bounds checking here
      add "if ((p < data) || (p > (data+SIZE*sizeof(int)))) {\n";
      add '  printf("data pointer out of bounds\\n"); \n';
      add "  exit(1);\n";
      add "}\n";
      add "(*p)++;";
    }
    "-" { 
      # also do bounds checking here
      clear; add "(*p)--;";
    }
    "." { clear; add "putc(*p, stdout);"; }
    "," { 
      clear; 
      # also check for getc == EOF
      # which can also mean an error
      add "if (feof(stdin)) { exit(0); } \n";
      add "if (*p == EOF) { exit(1); } \n";
      add "*p = getc(stdin);";
    }
    put; clear;
    add "com*"; push; .reparse
  }

  "[","]" { 
    put; add "*"; push; 
    add "unbalanced bracket '"; --; get; add "' ";
    add "near line:char "; lines; add ":"; chars; put; ++; clear; 
    .reparse
  }

  # ignore any other character but parse as a dummy command
  # so that the ignored char will end up in the output.
  !"" {  
    #*
    replace "\n" "\\n"; replace "\t" "\\t";
    replace "\f" "\\f"; replace "\r" "\\r";
    put; clear; add "// ignored character '"; get; add "'";
    put; clear; add "com*"; push;
    *#
    clear;
  } 

parse>

  # for debugging, add a c-style comment 
  add "// line "; lines; add " char "; chars; add ": "; print; clear; 
  unstack; print; stack; add "\n"; print; clear;

  pop; pop;

  # brackets with nothing in them is really an error because 
  # can create an infinite loop and does nothing anyway.
  "[*]*" {
    clear;
    add "Empty bracket '[]' ";
    add "near line:char "; lines; add ":"; chars; add "\n";
    print; quit;
  }

  "com*com*","comset*com*" {
    clear; get; add "\n"; ++; get; --; put; clear;
    add "comset*"; push; .reparse
  }  

  pop;
  "[*com*]*","[*comset*]*" {
    # indent the braced code
    clear; add "  "; ++; get; replace "\n" "\n  "; put;
    clear; add "while (*p > 0) {\n";
    get; --; add "\n}"; put;
    clear; add "com*"; push; .reparse
  }

  (eof) {
    "com*","comset*" {
      clear; 
      # indent the generated code
      add "  "; get; replace "\n" "\n  "; put; clear;
      add "/* Code translated from the 'Brainf***' esoteric language \n";
      add "   by the pep/nom parser with the script: \n";
      add "   bumble.sf.net/books/pars/eg/brainf.toclang.pss */\n\n";
      add "#include <stdio.h>\n";
      add "#include <stdlib.h>\n";
      add "#define SIZE 65000 \n";
      add "int main(int argc, char *argv[]) {\n";
      add "  int data[SIZE];\n";
      add "  int* p = data;\n";
      get; 
      add "\n}\n"; print; quit;
    }
    "[*comset*","[*com*",B"[*[*" {
      # get the saved error message from the [ token cell
      clear; get; add "\n"; print; quit;
    }
    "comset*]*","com*]*",E"]*]*" {
      # get the saved error message from the ] token cell
      clear; ++; get; add "\n"; print; quit;
    }
    put;
    add "
   The 'Brainf' code didnt parse well:
   Legal Brainf commands are 
     > increment pointer 
     < decrement pointer
     + increment value at pointer
     - [ ] . , 
     (optional command) '#' print state
   Everything else is ignored. 
   The input parsed as tokens:\n  "; print; clear;
   get; add "\n"; 
    print; quit;
  }
  push; push; push;