标签：nbsp 课堂 select first 练习 size sele sel fir
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‘|ε
T→FT‘
T‘→*FT‘|ε
F→(E)|i
FIRST集:
FIRST(TE‘)={T}
FIRST(+TE‘)={+}
FIRST(ε)={ε}
FIRST(FT‘)={F}
FIRST(*FT)={*}
FIRST((E))={(}
FIRST(i)={i}
FOLLOW集:
FOLLOW(T)={E‘}
FOLLOW(E)={)}
FOLLOW(E‘)={#}
FOLLOW(F)={#}
FOLLOW(T‘)={#}
SELECT集:
SELECT(E→TE‘)={T}
SELECT(E‘→+TE‘)={+}
SELECT(E‘→ε)=(FIRST(ε)-{ε})∪FOLLOW(E‘) = {)}
SELECT(T→FT‘)={F}
SELECT(T‘→*FT‘)={*}
SELECT(T‘→ε)=(FIRST(ε)-{ε})∪FOLLOW(T‘) = {ε}
SELECT(F→(E))={(}
SELECT(F→i)={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→aABe|a
B→Bb|d
消除左递归：
A→aA‘
A‘→ABe|ε
B→dB‘
B‘→bB‘|ε
FIRST集:
FIRST(aA‘)={a}
FIRST(ABe)={A}
FIRST(ε)={ε}
FIRST(dB‘)={d}
FIRST(bB‘)={b}
FOLLOW集:
FOLLOW(A)={B}
FOLLOW(A‘)={#}
FOLLOW(B)={#}
FOLLOW(B‘)={#}
SELECT集:
SELECT(A→aA‘)={a}
SELECT(A‘→ABe)={A}
SELECT(A‘->ε)=(FIRST(ε)-{ε})∪FOLLOW(A‘)={ε}
SELECT(B→dB‘)={d}
SELECT(B‘→bB‘)={b}
SELECT(B‘->ε)=(FIRST(ε)-{ε})∪FOLLOW(B‘)={ε}
(3) S→Aa|b
A→SB
B→ab
代入得：S→SBa|b
消除左递归：
S→bS‘
S‘→BaS‘|ε
B→ab
FIRST集:
FIRST(bS‘)={b}
FIRST(BaS‘)={B}
FIRST(ε)={ε}
FIRST(ab)={a}
FOLLOW集:
FOLLOW(S)={#}
FOLLOW(S‘)={#}
FOLLOW(B)={a}
SELECT集:
SELECT(S→bS‘)={b}
SELECT(S‘→BaS‘)={B}
SELECT(S‘->ε)=(FIRST(ε)-{ε})∪FOLLOW(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(S)={#}
FOLLOW(A)={p}
SELECT集:
SELECT(S->Ap)={a,c,p}
SELECT(A->a)={a}
SELECT(A->ε)=(FIRST(ε)-{ε})∪FOLLOW(A)={p}
SELECT(A->cA)={c}
SELECT(A->aA)={a}
S->Ap
S->Bq
A->a
A->cA
B->b
B->dB
FIRST集:
FIRST(Ap)={a,c}
FIRST(Bq)={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)={a,c}
SELECT(S->Bq)={b,d}
SELECT(A->a)={a}
SELECT(A->cA)={c}
SELECT(B->b)={b}
SELECT(B->dB)={d}
标签：nbsp 课堂 select first 练习 size sele sel fir
原文地址：https://www.cnblogs.com/momo-er/p/11847716.html
