anchor.diff:   * Simone Tripodi,21.11.2007 Replaced parser literal IRI_REF by lexer tokens as preparation for AST generation
    * Jrgen Pfundt, 25.11.2007 The A token is case insensitive now as requested by the w3.org rdf-sparql-query
    *                           document
  + * Jrgen Pfundt, 18.01.2008 Made EXPONENT a fragment.
  + *                           Added missing backslash to fragment ECHAR as defined by the w3.org rdf-sparql-query
  + *                           document.
    *
    */
   
  
positive.code: 
  fragment
  EOL
      : '\n'| '\r'
      ;
  
  REFERENCE
  
negative.code:     : MINUS DOUBLE
      ;
  
  fragment
  EXPONENT
      : ('e'|'E') (PLUS|MINUS)? DIGIT+
      ;
  