✎ soc:2009:lynusvaz:notes:start

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====== Lynus Vaz: Enhanced scripting language ======
===== Notes =====
I've taken a few ideas from Fabrice Bellard's C OTCC compiler: http://bellard.org/otcc/

Also looking at [[http://www.gnu.org/software/bash/bash.html|bash]]

Here's the POSIX specification for the shell: [[http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html]]

And the PXE specification: [[http://www.pix.net/software/pxeboot/archive/pxespec.pdf]]

Proposed syntax:
  
  LINES           => LINE '\n' LINES | e
  LINE            => WORD | WORD WS ARG_LIST | e
  ARG_LIST        => ARG WS ARG_LIST | e
  ARG             => WORD
  SP              => ' ' | '\t'
  WS              => SP | SP WS
  NOT_EXP         => (any - { SP, '$(', ')', '${', '}')    /* Represents characters not expanded */
  WORD            => NOT_EXP WORD | EXP WORD | NOT_EXP | EXP
  EXP             => EXPR_EXP | VAR_EXP                /* Expansions */
  EXPR_EXP        => '$(' EXPR ')'
  VAR_EXP         => '${' (any - { '}' })+ '}'       
  EXPR            => TERM | TERM BIN_OP EXPR | MONO_OP EXPR
  TERM            => VAR_EXP | STRING
  NUM             => ('+' | '-' )? ( '(' EXPR ')' | (digit)+ )               
  STRING          => (any - { '$(', ')', '${', '}', ' ', BIN_OP, MONO_OP})+    /* This will help with string comparison */
  BIN_OP          => '*' |  '/' | '%'             /* Convert both operands to integers */
                     | '+' | '-'
                     | '<<' |  '>>'
                     | '<' | '<=' | '>' | '>='
                     | '!=' | '=='                          /* Should also work for strings */
                     | '&'
                     | '|'
                     | '^'
                     | '&&'
                     | '||'
  MONO_OP         => '~' | '!'

Syntax for if-else branches:
  if <condition>
      <statements>
  [ else
      <statements> ]
  fi

Proposed syntax for while loops:
  while <condition>
  do
      <statements>
  done

Proposed syntax for for loops:
  for <variable> in <value list>
  do
      <statements>
  done
Pretty similar to the shell syntax, so it should be familiar.

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