门|门CS 2012 |第 65 题

对于下面的语法，部分 LL(1) 解析表也随语法一起呈现。需要填写的条目表示为E1、E2和E3。 $\epsilon$是空字符串，$ 表示输入结束，而，|分隔作品的交替右侧。

(一) A
(乙)乙
(C)丙
(四)丁答案：(一)
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