构造语法树的语法制导定义 产生式 语义规则 E>E1+T Enptr=mkNode(+, Er.nptr, T nptr) E→T Enptr=Tnptr 7→T*FTp= mknode(·*,T,pm,F,pm) T→F Tnptr= Fnptr F→(E)F,npt=E,pt F→)id Fnptr= mkleaf(id, identry) F->num Fnptr= mkLeaf(num, num. val构造语法树的语法制导定义 产 生 式 语 义 规 则 E → E1 + T E.nptr = mkNode( ‘+’, E1 .nptr, T.nptr) E → T E.nptr = T.nptr T → T1  F T.nptr = mkNode( ‘’, T1 .nptr, F.nptr) T → F T.nptr = F.nptr F → (E) F.nptr = E.nptr F → id F.nptr = mkLeaf (id, id.entry) F → num F.nptr = mkLeaf (num, num.val)