Hi Monty, Thanks for your fast response. BTW, the parser still stuck even I use the file as input. When I try with input: (1+2),(1+3); NUM_INT term PLUS NUM_INT term simpleExpr expr ( expr ) term simpleExpr expr <---- end, the COMMA and (1+3) is not process Best Regards jagad Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/