门| GATE CS 2012 |第65章

对于下面的语法，还提供了部分LL(1)解析表以及该语法。需要填写的条目分别表示为E1，E2和E3。 $\epsilon$是空字符串，$表示输入的结尾，并且|分隔作品的其他右侧。

(A) A
(B) B
(C) C
(D) D答案： (A)
解释：

First(X) - It is the set of terminals that begin the 
            strings derivable from X.

Follow(X) - It is the set of terminals that can appear
            immediately to the right of X in some sentential
            form.

Now in the above question,

FIRST(S) = { a, b, epsilon}
FIRST(A) = FIRST(S) = { a, b, epsilon}
FIRST(B) = FIRST(S) = { a, b, epsilon}
FOLLOW (A) = { b , a }
FOLLOW (S) = { $ } U FOLLOW (A) = { b , a , $ }
FOLLOW (B) = FOLLOW (S) = { b ,a , $ }

epsilon corresponds to empty string.

这个问题的测验