PLUS -> "+"
MULT -> "*"
CB -> ")"
OB -> "("
##
ID -> ([0 - 9])+
##
##
EOL -> \n|\r
SPACE -> \s|\t
##
start -> { global stack result;} E {print " = "+string(pop(result)); }
E -> E <PLUS> T  { result.push(pop(result)+pop(result));  }
E -> T 
T -> T <MULT> F { result.push(pop(result)*pop(result));  }
T -> F
F -> <OB>  E <CB> 
F -> <ID> {print lexeme; result.push(int(lexeme));}