带参数的 Prolog DCG

Question

我不知道如何使用参数来处理 DCG。假设我们想用 DCGs 来表示 parents 和它们的 children，那么我们可以说：

father --> [Peter].
mother --> [Isabel].

child --> [Guido].
child --> [Claudia].

verb --> [is].
relation --> [father, of].
relation --> [mothter, of].

s --> father, verb, relation, child.
s --> mother, verb, relation, child.

然后您可以通过以下方式查询：?- s([Peter, is, father, of, Guido], []). Which returns true.

我如何通过说 father(name).

在 DCG 上使用参数

Answer 1

添加参数很容易，如果您按照下面的方式进行，但无法使查询正常工作，我也不会感到惊讶。这样做的诀窍是知道 DCG 被翻译成常规 Prolog，方法是在将两个额外的参数转换为 Prolog 时将两个额外的参数线程化到每个谓词。它们可以随心所欲地命名，我个人更喜欢 S0 和 S 作为状态，但如果它们具有更具体的含义，请更改它们。

在下面的代码中也需要注意，因为名称以大写字母开头并且它们必须是原子，而不是使用 peter，原子以 ' 结尾，例如'Peter'.

father('Peter') --> ['Peter']. 
mother('Isabel') --> ['Isabel'].

child('Guido') --> ['Guido']. 
child('Claudia') --> ['Claudia'].

verb(is) --> [is]. 
relation('father of') --> [father, of]. 
relation('mother of') --> [mother, of].

s --> father(Father), verb(Verb), relation(Relation), child(Child). 
s --> mother(Father), verb(Verb), relation(Relation), child(Child).

现在检查您的第一个查询：

?- s([Peter, is, father, of, Guido], []).
true ;
true ;
true ;
true.

对于阅读这篇文章的其他人来说，这是相同的答案，但没有添加参数。有疑问就去看看吧

现在使用添加的隐藏参数的父亲查询。

?- father(Father,S0,S).
Father = 'Peter',
S0 = [_5662|S].

你也可以

?- father(Father,_,_).
Father = 'Peter'.

旁注：

更好的方法是使用 phrase/2 or phrase/3，我说使用而不是回答，因为你问的是如何查询子句父亲的问题，而不是用它来解析数据或使用短语谓词。

test :-
    DCG = father(Father),
    phrase(DCG,Input,Rest),
    format('Father: ~w~n',[Father]).

?- test.
Father: Peter
true.

或

?- phrase(father(Name),_).
Name = 'Peter'.

这些也有效

?- s(S0,S).
S0 = ['Peter', is, father, of, 'Guido'|S] ;
S0 = ['Peter', is, father, of, 'Claudia'|S] ;
S0 = ['Peter', is, mother, of, 'Guido'|S] ;
S0 = ['Peter', is, mother, of, 'Claudia'|S] ;
S0 = ['Isabel', is, father, of, 'Guido'|S] ;
S0 = ['Isabel', is, father, of, 'Claudia'|S] ;
S0 = ['Isabel', is, mother, of, 'Guido'|S] ;
S0 = ['Isabel', is, mother, of, 'Claudia'|S].

?- s(S0,[]).
S0 = ['Peter', is, father, of, 'Guido'] ;
S0 = ['Peter', is, father, of, 'Claudia'] ;
S0 = ['Peter', is, mother, of, 'Guido'] ;
S0 = ['Peter', is, mother, of, 'Claudia'] ;
S0 = ['Isabel', is, father, of, 'Guido'] ;
S0 = ['Isabel', is, father, of, 'Claudia'] ;
S0 = ['Isabel', is, mother, of, 'Guido'] ;
S0 = ['Isabel', is, mother, of, 'Claudia'].

?- phrase(s,S,[]).
S = ['Peter', is, father, of, 'Guido'] ;
S = ['Peter', is, father, of, 'Claudia'] ;
S = ['Peter', is, mother, of, 'Guido'] ;
S = ['Peter', is, mother, of, 'Claudia'] ;
S = ['Isabel', is, father, of, 'Guido'] ;
S = ['Isabel', is, father, of, 'Claudia'] ;
S = ['Isabel', is, mother, of, 'Guido'] ;
S = ['Isabel', is, mother, of, 'Claudia'].

如果您使用 listing/0，您可以看到 DCG 转换为 Prolog，这将显示通过谓词串接的两个额外参数。

?- listing.  

child('Guido', ['Guido'|A], A).
child('Claudia', ['Claudia'|A], A).

verb(is, [is|A], A).

relation('father of', [father, of|A], A).
relation('mother of', [mother, of|A], A).

father('Peter', ['Peter'|A], A).
mother('Isabel', ['Isabel'|A], A).

s(A, B) :-
    father(Father, A, C),
    verb(Verb, C, D),
    relation(Relation, D, E),
    child(Child, E, B).
s(A, B) :-
    mother(Father, A, C),
    verb(Verb, C, D),
    relation(Relation, D, E),
    child(Child, E, B).

test :-
    DCG=father(Father),
    phrase(DCG, Input, Rest),
    format('Father: ~w~n', [Father]).

true.

带参数的 Prolog DCG

Prolog DCG with arguments

arguments

prolog

dcg