使用带有Logtalk对象方法的"univ“Prolog谓词作为参数

Question

如何使用以Logtalk对象方法为参数的'Univ(http://www.swi-prolog.org/pldoc/doc_for?object=(%3D..%29/2)‘( =../2 ) prolog谓词？

请考虑以下代码：

baz(foo(X)) :-
  write(predicate), write(X), nl.

run :-
    Term =.. [baz, foo(testfoo)],
    write(Term), nl, Term,nl,    
    TermLgt =.. [bar::baz, foo(testfoo2)],
    write(TermLgt), nl, Term,nl.    

:- object(bar).

  :- public(baz/1).
  baz(foo(X)) :-
    write(method), write(X), nl.

:- end_object.

:- object(main).

  :- public(run/0).
  run :-
    Term =.. [baz, foo(testfoo)],
    write(Term), nl, Term,nl,    
    TermLgt =.. [bar::baz, foo(testfoo2)],
    write(TermLgt), nl, Term,nl.

:- end_object.

我会得到：

?- {myfile}.
% (0 warnings)
true.

?- run.
baz(foo(testfoo))
predicatetestfoo

ERROR: =../2: Type error: `atom' expected, found `bar::baz' (a compound)

?- main::run.
baz(foo(testfoo))
ERROR: Undefined procedure: baz/1
ERROR:   However, there are definitions for:
ERROR:         baz/1

什么样的解决办法可以用来进行良好的解释/编译？像predsort/3 (先排序/3文档)这样的swi构建谓词似乎也存在同样的问题。

Answer 1

标准的=../2谓词在从list构造术语时期望第一个list参数是一个原子，但是bar::baz是一个带有函子::/2的复合词(对于顶级查询和加载Logtalk时都定义为谓词)。解决方案是编写以下内容：

baz(foo(X)) :-
    write(predicate), write(X), nl.


run :-
    Term =.. [baz, foo(testfoo)],
    write(Term), nl, call(Term), nl,    
    TermLgt =.. [::, bar, Term],
    write(TermLgt), nl, call(Term), nl.    


:- object(bar).

    :- public(baz/1).
    baz(foo(X)) :-
        write(method), write(X), nl.

:- end_object.


:- object(main).

    :- public(run/0).
    run :-
        Term =.. [baz, foo(testfoo)],
        write(Term), nl, Term,nl,    
        TermLgt =.. [::, bar, Term],
        write(TermLgt), nl, Term,nl.

:- end_object.

通过这些更改，您可以得到：

?- {univ}.
% [ /Users/pmoura/Desktop/univ.lgt loaded ]
% (0 warnings)
true.

?- run.
baz(foo(testfoo))
predicatetestfoo

bar::baz(foo(testfoo))
predicatetestfoo

true.