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soc:2009:lynusvaz:notes:start [2009/05/17 07:52]
127.0.0.1 external edit
soc:2009:lynusvaz:notes:start [2009/08/15 08:40]
lynusvaz
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 ====== Lynus Vaz: Enhanced scripting language ====== ====== Lynus Vaz: Enhanced scripting language ======
- 
 ===== Notes ===== ===== Notes =====
 +[[.:​scripting_doc:​Features added|Documenting the new features]]
 +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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