Question

我已经实现了几个链规则，以便最后一条规则根据前一条规则的结果获得所需的结果。

rule1(X,Y) :-
   pred1(X,Z),
   pred1(Y,Z).

rule2(Z,T) :- 
   rule1(X,Y),
   pred2(Z,X),
   pred2(T,Y).

我需要获得每个规则推断的每个事实。我是使用jpl库从Java做的。

String stringFileQuery = "rule1(X,Y)";
System.out.println(stringFileQuery + " "
   + (Query.hasSolution(stringFileQuery) ? "succeeded" : "failed"));
Query fileQuery = new Query(stringFileQuery);
System.out.println("all solutions of " + stringFileQuery);
while (fileQuery.hasMoreSolutions()) {
    Map<String, Term> s10 = fileQuery.nextSolution();
    System.out.println("First -> " + s10.get("X") + ", Second ->" + 10.get("Y"));
}

即使在Prolog中，我怎样才能获得所有这些事实？在真实的程序中，我有两个以上的规则。

Answer 1

你在这里寻找的是Prolog的meta-interpreter，它记录了事实。由于Prolog是一种homoiconic语言，因此编写一个简单的元解释器是trivial。

您可能希望使用clause_property/2检查您正在检查的条款是否是事实，如此

recordFacts(Goal, [Goal|Facts]) :-
    clause(Goal, _Body, Ref),
    clause_property(Ref, fact).

修改

一个完整的例子就像是

recordFacts(Goal, Facts) :-
    recordFacts(Goal, [], AllFacts),
    list_to_set(AllFacts, Facts).

recordFacts((Goal, RestOfGoals), FactsIn, FactsOut) :-
    recordFacts(Goal, FactsIn, FactsH),
    recordFacts(RestOfGoals, FactsH, FactsOut).

recordFacts(Goal, Facts, [Goal|Facts]) :-
    clause(Goal, _, Ref),
    clause_property(Ref, fact).

recordFacts(Goal, FactsIn, FactsOut) :-
    clause(Goal, Body, Ref),
    not(clause_property(Ref, fact)),
    not(clause_property(Ref, predicate(system: (',')/2))),
    recordFacts(Body, FactsIn, FactsOut).

如何检索在Prolog中推断链规则的所有事实

1 个答案:

修改