Prolog Left Corner Parser调试求助：特定句子解析失败排查

我是Prolog初学者，针对句子**"The little pigs were safe inside"**编写了左上角解析器（Top Left Corner Parser），但运行测试后解析失败。以下是我的代码、测试跟踪日志及期望输出，恳请帮忙定位问题并指明解决方向。

问题代码 #

% The little pigs were safe inside.

% ------------------------------------------------  TERMINALS  ------------------------------------------------

leaf(determiner) --> [the].

leaf(adjective) --> [little].

leaf(adjective) --> [safe].

leaf(noun) --> [pigs].

leaf(verb) --> [were].

leaf(adverb) --> [inside].

% ------------------------------------------------  NON-TERMINALS   ------------------------------------------------

lcd(noun_phrase,sentence):-!.
lcd(determiner,noun_phrase):-!.
lcd(adjective,adjective_phrase):-!.
lcd(adverb,adjective_phrase):-!.
lcd(verb,verb_phrase):-!.
lc(X,X):-!.
lc(X,Y):-lcd(X,Y),!.
lc(X,Y):-lcd(X,Z),lc(Z,Y).

% ------------------------------------------------  RULES   ------------------------------------------------

parse(Nterm,As,[W0|W1],Wn):-
    leaf(Pterm,[W0|W1],W1),
    lc(Pterm,Nterm),
    Ap=..[Pterm,W0],
    P=..[Pterm,Nterm,Ap,As,W1,Wn],
    call(P).

noun_phrase(Nt,NP,As)-->{lc(sentence,Nt)},parse(verb_phrase, VP),sentence(Nt,sentence(NP,VP),As),!.
noun_phrase(noun_phrase,E,E)-->[]).

determiner(Nt,D,As)-->{lc(noun_phrase,Nt)},parse(adjective_phrase,N),noun_phrase(Nt,noun_phrase(D,N),As).

adjective(Nt,A,As)-->{lc(adjective_phrase,Nt)},parse(adjective_phrase,N),adjective_phrase(Nt,adjective_phrase(A,N),As).

adverb(Nt,A,As)-->{lc(adjective_phrase,Nt)},parse(adjective_phrase,N),adjective_phrase(Nt,adjective_phrase(A,N),As).

noun(Nt,N,As)-->{lc(adjective_phrase,Nt)},adjective_phrase(Nt,adjective_phrase(N),As).
adjective_phrase(adjective_phrase,A,A)-->[]).

verb(Nt,V,As)-->{lc(verb_phrase,Nt)},parse(noun_phrase,N),verb_phrase(Nt,verb_phrase(V,N),As).
verb(Nt,V,As)-->{lc(verb_phrase,Nt)},verb_phrase(Nt,verb_phrase(V),As).
verb_phrase(verb_phrase,A,A)-->[]).
sentence(s,A,A)-->[]).

test(S,A):-parse(S,A,[the, little, pigs, were, safe, inside],[]).

测试跟踪日志 #

trace,test(S,A).
Call: (9) test(_4648, _4650) ? creep
Call: (10) parse(s, _4650, [the, little, pigs, were, safe, inside], []) ? creep
Call: (11) leaf(_5024, [the, little, pigs, were, safe, inside], [little, pigs, were, safe, inside]) ? creep
Exit: (11) leaf(determiner, [the, little, pigs, were, safe, inside], [little, pigs, were, safe, inside]) ? creep
Call: (11) lc(determiner, s) ? creep
Call: (12) lcd(determiner, s) ? creep
Fail: (12) lcd(determiner, s) ? creep
Redo: (11) lc(determiner, s) ? creep
Call: (12) lcd(determiner, _5026) ? creep
Exit: (12) lcd(determiner, noun_phrase) ? creep
Call: (12) lc(noun_phrase, s) ? creep
Call: (13) lcd(noun_phrase, s) ? creep
Fail: (13) lcd(noun_phrase, s) ? creep
Redo: (12) lc(noun_phrase, s) ? creep
Call: (13) lcd(noun_phrase, _5026) ? creep
Exit: (13) lcd(noun_phrase, sentence) ? creep
Call: (13) lc(sentence, s) ? creep
Call: (14) lcd(sentence, s) ? creep
Fail: (14) lcd(sentence, s) ? creep
Redo: (13) lc(sentence, s) ? creep
Call: (14) lcd(sentence, _5026) ? creep
Fail: (14) lcd(sentence, _5026) ? creep
Fail: (13) lc(sentence, s) ? creep
Fail: (12) lc(noun_phrase, s) ? creep
Fail: (11) lc(determiner, s) ? creep
Redo: (11) leaf(_5024, [the, little, pigs, were, safe, inside], [little, pigs, were, safe, inside]) ? creep
Fail: (11) leaf(_5024, [the, little, pigs, were, safe, inside], [little, pigs, were, safe, inside]) ? creep
Fail: (10) parse(s, _4650, [the, little, pigs, were, safe, inside], []) ? creep
Fail: (9) test(_4648, _4650) ? creep
false.

期望输出 #

S = [the, little, pigs, were, safe, inside],A = s(np(d(the), adjp(adj(little), n(pigs))), vp(v(were), adjp(adj(safe), adv(inside)))) .

问题定位与解决方向 #

1. 语法错误修正：所有DCG规则末尾存在多余的右括号，需删除：

   • 将noun_phrase(noun_phrase,E,E)-->[]).改为noun_phrase(noun_phrase,E,E)-->[]
   • 将adjective_phrase(adjective_phrase,A,A)-->[]).改为adjective_phrase(adjective_phrase,A,A)-->[]
   • 将sentence(s,A,A)-->[]).改为sentence(s,A,A)-->[]

2. Top Left Corner链缺失映射：
   跟踪日志显示lc(sentence, s)失败，因为lcd规则中没有定义sentence到s的映射。需在lcd规则中添加：

   lcd(sentence, s):-!.
   

   这样就能打通determiner → noun_phrase → sentence → s的合法链，解决初始匹配失败问题。

3. DCG规则与普通谓词调用不匹配：
   代码中parse是普通4参数谓词，但在DCG规则（如noun_phrase）中直接以parse(verb_phrase, VP)形式调用，缺少输入输出列表参数，导致参数数量不匹配。需将parse重构为DCG谓词，或在调用时显式传递列表参数：

   % 重构parse为DCG形式
   parse(Nterm, As) -->
       [W0],
       {leaf(Pterm, [W0], [])},
       {lc(Pterm, Nterm)},
       {Ap =.. [Pterm, W0]},
       call(Pterm, Nterm, Ap, As).
   

   同时调整所有DCG规则中对parse的调用，使其符合DCG语法。

4. 非终结规则参数与构造调用匹配：
   检查determiner、adjective等非终结规则的参数，确保与parse中构造的call(P)调用参数一致，避免参数数量或语义不匹配。

内容的提问来源于stack exchange，提问作者Vlad Timu