Hi, > expr : bool_exprsn; > It works fine with expression such as (iVar1 < > 10)&(iVar3 > 4) etc. However it does not throw > exceptions for expression such as > (iVar1 < 10))))) Just change your expr rule to be expr : bool_exprsn EOF; Bests, Rodrigo Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/