Minor quirks

[Tony Wilson-3]

Happy New Year to All.

%=== 1 ===%

While trying unknown_predicate_handler/3 and unknown/2 to use in a
dynamic clause loader which reads clauses from an indexed file, asserts
and retries the failed goal, I found that unknown_predicate_handler/3
fails with a clause that has a body:

%unknown_predicate_handler(X,_,X) :- asserta((q(456))). % works
%unknown_predicate_handler(X,_,X) :- asserta((q(456) :- true)). % works
unknown_predicate_handler(X,_,X) :- asserta((q(456) :-
        write(123))). % asserts but fails

%retry(X) :- asserta((q(456) :- write(123))), X. % works
%:-     unknown(_,retry(_)).

:- q(X),write(X),nl.
:- listing(q/1).
:- q(X),write(X),nl.
:- listing(q/1).

%=== 2 ===%

Example code in Chapter 21: C Language interface to YAP (pdf page 199)
has errors:

        YAP_dogoalinfo goalInfo;
// manual error YAP_ArraysOfTerm -> YAP_ArgsOfTerm
  YAP_Term *goalArgs = YAP_ArgsOfTerm(g);
           // manual error YAP_Functor * -> YAP_Functor
        YAP_Functor goalFunctor = YAP_FunctorOfTerm(g);
  // manual error YAP_FunctorToGoal -> YAP_FunctorToPred
        YAP_PredEntryPtr goalPred = YAP_FunctorToPred(goalFunctor);
        int result = YAP_EnterGoal( goalPred, goalArgs, &goalInfo );
        while (result)
                result = YAP_RetryGoal( &goalInfo );
        YAP_LeaveGoal(TRUE, &goalInfo);

%=== 3 ===%

When using YAP_RunGoal or YAP_RunGoalOnce in Yap->C->Yap:

:- c_function(X), % which calls yap predicate via RunGoal/Once
        write(X),nl.

worked ok but

a :- c_function(X),
        write(X),nl.

:- a.

would do 2 writes with one having a mystery value.

If this is not a known problem, I will supply full example if needed.

%=========%

Regards,
Tony.



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