anchor.diff:      ;
   
   ASSIGNMENT : ':=' ;
  +
  +/* Operators */
  +
  +CONCAT : '||' ;
   EQ : '='  ;
   NE : '<>' ;
   LE : '<=' ;
  
positive.code: 
  WS : [ \n\r\t\u000C] -> skip ;
  COMMENT : '/*' .*? '*/' -> skip;
  
  
negative.code: 
  variable : ( ESCAPED_IDENTIFIER | REG_IDENTIFIER ) ;
  
  operatorConcat : op=CONCAT ;
  
  // Literal.
  litteral : nullLiteral
           | booleanLiteral
           | dateLiteral
           | integerLiteral
           | floatLiteral
           | stringLiteral ;
  
  nullLiteral     : NULL_CONSTANT ;
  booleanLiteral  : BOOLEAN_CONSTANT ;
  dateLiteral     : 'TODO:date' ;
  integerLiteral  : INTEGER_CONSTANT ;
  floatLiteral    : FLOAT_CONSTANT ;
  stringLiteral   : STRING_CONSTANT ;
  
  assignment : variable ASSIGNMENT expression ;
  
  