按照语法集

Question

我正在尝试计算以下语法的FOLLOW集：

E -> TX
T -> int Y | ( E )
X -> + E | ε
Y -> * T | ε

到目前为止，我已经计算了以下FOLLOW设置：

follow (E) = {$} U {)}
follow (Y) = follow (T)
follow (T) = follow (Y)
follow (X) = follow (E) = {$, )}
follow (E) = first ()) = {)}

我知道跟随（T）/跟随（Y）包含{+，$，）}但我很难达到这一点。

在这里解释方法的任何帮助都会非常有帮助。

注意：我遵守了这些规则

1)  If A is the start symbol put $ in Follow (A)
2)  If there is a production B -> αAb, then Follow (A) = First (b) 
3)  If there is a production B -> aA or B -> αAb where First (b) is ε, add Follow (A) = Follow (B)

Answer 1

我已经明白了（并且花了下午的大部分时间）！

因此，我发现这个的规则是：

follow(E) = follow(T)
follow(E) = first ())
follow(X) = follow(E)
follow(Y) = follow(T)
**follow(T) = first(X)** //the important one!

遵循这些规则，您可以构建集合：

follow(E) = {$, )}
follow(T) = {$, ), +}
follow(X) = {$, )}
follow(Y) = {$, ), +}

结论语法的后续集合结束了！