1.已知文法:
S->a|^|(T)
T->T,S|S
分析句型(T,(^,a)),求全部的短语、直接短语和句柄
解:S->(T)->(T,S)->(T,(T))->(T,(T,S))->(T,(S,S))->(T,(^,S))->(T,(^,a))
语法树:
全部短语:(T,(^a)) T,(^,a) (^,a) ^,a ^ a
直接短语:a ^
句柄:^
2.构造上下文无关文法,描述语言:
{anbn|n>=0}
{ambn|m>=n>=0}
{(ab)n|n>=0}
{ambn|m,n>=1}
解:
(1)对应文法为G(S):S->ab|aSb|ε
(2)对应文法为G(S):S->aSb|aS|ε
(3)对应文法为G(S):S->ab|abS|ε
(4)对应文法为G(S):S->ab|aS|bS|aSb
3.如果if语句的方法:
stmt->if expr then stmt
| if expr then stmt else stmt
| other
句子if E1 then if E2 then S1 else S2是否有两棵不同的语法树?说明了什么?
解: