anchor.diff:  ufloatConst : integer=NUMBER? '.' (fraction=NUMBER | fractionE=FLOAT_FRAC exponent=fixedConst)? ;
   floatConst  : sign? unsigned=ufloatConst ;
   
  -sign : (PLUS|MINUS);
  +sign  : (PLUS|MINUS);
  +mulOp : (MUL|DIV);
   
   
   // lexer rules
  
positive.code: }
  }
  
  // parser rules
  
  program : card*;
  
negative.code: 
  PLUS  : '+';
  MINUS : '-';
  MUL   : '*';
  DIV   : '/';
  POWER : '**';
  
  // return newlines to parser
  NEWCARD : '\r'? '\n' ;
  