Re: determinism

[Daniel Diaz]

michel levy a écrit :
> Could you help to write this program :
> det(T,G) succeeds if and only if G succeeds once and only once and give
> the T answer.
> 1) I don't want the solution below by findall, because I want to try at
> most two back tracks on G.
> det(T,G) :- findall(T,G,L),length(L,1)
> 
> 2) I know already call_det but it's not the solution because G can have
> choice points, but only one answer.
> 

You can do it using a global variable to count solutions. Stop when the
second is reached.


det(Goal) :-
        det1(Goal).

det(_) :-
        g_read(det_count, 1).
        

det1(Goal) :-
        g_assign(det_count, 0),
        call(Goal),
        g_inc(det_count, Count), % increment and return the counter
        Count = 2,      % cut if 2nd solution is reached (else fail)
        !,
        fail.

Hope this helps



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