I know N = X | N Y could be converted to N = X (Y)* Now a grammar is N = X | N Y N, should it be converted to N = X (Y N)* or N = X (Y X)* ? Thanks. Jigang ___________________________________________________________ 抢注雅虎免费邮箱-3.5G容量,20M附件! http://cn.mail.yahoo.com