anchor.diff:  FALSE: 'false';
   ALIAS: 'alias';
   LET: 'let';
  +SCOPE_LEAVE: 'scope_leave'; // code block run at leaving scope
  +END_SCOPE_LEAVE: 'end_sl';
   
   // literals
   fragment ESC: '\\"' | '\\\\';
  
positive.code: BAND: '&';
  OR: 'or';
  AND: 'and';
  XOR: 'xor'; // only binary
  EQUALS: '==';
  NOT_EQ: '!=';
  ASSIGN: '=';
  
negative.code: STATIC_IF: 'static_if';
  THEN: 'then';
  ELSE: 'else';
  ENDIF: 'end_if';
  UNIT: 'unit';
  PLUS: '+';
  MINUS: '-';
  