标签：psi 文法 nbsp select cup first sel 递归 follow
1.将以下文法消除左递归，分析符号串 i*i+i 。
并分别求FIRST集、FOLLOW集，和SELECT集
E -> E+T | T
T -> T*F | F
F -> (E) | i
消除左递归：
E → TE‘
E‘ → +TE‘ | ?
T → FT‘ | ?
T‘ → *FT‘ | ?
F → (E) | i
2.P101练习7（2）（3）文法改写，并分别求FIRST集、FOLLOW集，和SELECT集
（2)A → baBe | ?
B → Bb | d
A → aA‘
A‘ → ABe | ?
B → dB‘
B‘ → bB‘ | ε
FIRST集：
FIRST(aA‘) = { a }
FIRST(ABe) = { A }
FIRST(?) = { ? }
FIRST(dB‘) = { d }
FIRST(bB‘) = { b }
FOLLOW集：
FOLLOW(A) = { e , # }
FOLLOW(A‘) = { e , # }
FOLLOW(B) = { d }
FOLLOW(B‘) = { d , # }
SELECT集：
SELECT(A → aA‘) = FIRST(aA‘) = { a }
SELECT(A‘ → ABe) = FIRST(ABe) = { a }
SELECT(C‘ → ε) = FIRST(ε) - { ε }∪FOLLOW(A‘) = { d , # }
SELECT(B → dB‘) = FIRST(dB‘) = { d }
SELECT(B‘ → bB‘) = FIRST(bB‘) = { b }
SELECT(B‘ → ε) = FIRST(ε) - {ε}∪FOLLOW(B‘) = { e }
(3)
S → Aa | b
A → SB
B → ab
S → SBa | b
S → bS‘
S‘ → BaS‘ | ε
B → ab
FIRST集：
FIRST(S) = { b }
FIRST(S‘) = {a , ε}
FIRST(bS‘) = { a , ε }
FIRST(B) = { a }
FOLLOW集：
FOLLOW(S) = { # }
FOLLOW(S‘) = { # }
FOLLOW(B) = { a }
SELECT集：
SELECT(S→bS‘) = FIRST(bS‘) = { a , ε }
SELECT(S‘→BaS‘) = { a , b }
SELECT(S‘→ε) = { # }
SELECT(B→ab) = { a }
课堂练习：
求以下文法的FIRST集、FOLLOW集和SELECT集。
S->Ap
A->a |ε
A->cA
A->aA
FIRST集：
FIRST(Ap) = { a , c , p }
FIRST(a) = { a }
FIRST(ε) = { ε }
FIRST(cA) = { c }
FIRST(aA) = { a }
FOLLOW集：
FOLLOW(A) = { p }
FOLLOW(S) = { # }
SELECT集：
SELECT(S→Ap) = FIRST(Ap) = { a , c , p }
SELECT(a) = FIRST(a) = { a }
SELECT(ε) = FOLLOW(A) = { p }
SELECT(cA) = FIRST(cA) = { c }
SELECT(aA) = FIRST(aA) = { a }
S->Ap
S->Bq
A->a
A->cA
B->b
B->dB
FIRST集：
FIRST(Ap) = { a , c }
FIRST(Bp) = { b , d }
FIRST(a) = { a }
FIRST(cA) = { c}
FIRST(b) = { b }
FIRST(dB) = { d }
FOLLOW集：
FOLLOW(S) = { # }
FOLLOW(A) = { p }
FOLLOW(B) = { q }
SELECT集：
SELECT(S->Ap) = FIRST(Ap) = { a , c }
SELECT(S->Bq) = FIRST(Bq) = { b , d }
SELECT(A->a) = FIRST(a) = { a }
SELECT(A->cA) = FIRST(cA) = { c }
SELECT(B->b) = FIRST(b) = { b }
SELECT(B->dB) = FIRST(dB) = { d }
标签：psi 文法 nbsp select cup first sel 递归 follow
原文地址：https://www.cnblogs.com/fzwboke/p/11869641.html
