用于描述算术表达式的文法定义 S-> NP VP VP->VNP epression erpression term NP-> NAME expression expression- term NP->ART N e pression→term NAME-> John term→term* factor V->ate term term/factor ART-> the N-> cat term actor actoN expression factor→id用于描述算术表达式的文法定义 8 S -> NP VP VP -> V NP NP -> NAME NP -> ART N NAME -> John V -> ate ART -> the N -> cat