anchor.diff:      GROUP '(' IDENTIFIER ')'
     | /* empty */
   ;
  +
  +range_option:
  +    RANGE '(' IDENTIFIER '=' ')'
  +;
  +
  +
   
   /*----------------------------------------------------------------------------
    * LEXER RULES
  
positive.code: 
  // Options
  GROUP        : 'group';
  
  // Special elements
  IDENTIFIER      : [a-zA-Z_$] [a-zA-Z_$0-9]* ;
  COMMA           : ',' ;
  NUMBER          : (DIGIT)+ ;
  fragment DIGIT  : '0'..'9' ;
  
  
negative.code: directive[ClawLanguage language]:
      LFUSION { $language.setDirective(ClawDirective.LOOP_FUSION); } group_option
    | LINTERCHANGE { $language.setDirective(ClawDirective.LOOP_INTERCHANGE); } '(' index_list ')'
    | LEXTRACT { $language.setDirective(ClawDirective.LOOP_EXTRACT); } range_option
    | REMOVE { $language.setDirective(ClawDirective.REMOVE); }
    | END REMOVE { $language.setDirective(ClawDirective.END_REMOVE); }
  ;
  