anchor.diff:  /* Core functions */
   
   NATIVE_FUNCTIONS : (NUMERIC_FUNCTIONS | STRING_FUNCTIONS ) ;
  -nativeFunctions : NUMERIC_FUNCTIONS
  -                | STRING_FUNCTIONS ;
  +
   FUNC_ISNULL : 'isnull' ;
   
   // Numeric
  
positive.code:     : dateFromStringFunction
      ;
  
  dateFromStringFunction : FUNC_D_F_S '(' componentRef ',' format=STRING_CONSTANT ')';
  
  
  // Left recursive
  
negative.code: FUNC_LOWER   : 'lower' ;
  FUNC_SUBSTR  : 'substr' ;
  FUNC_INSTR   : 'instr' ;
  // TODO: Fix conflict FUNC_D_F_S   : 'date_from_string' ;
  FUNC_REPLACE : 'replace' ;
  
  //WS : [ \r\t\u000C] -> skip ;
  