Re: Problem with SWI-Prolog

SRocha schreef in comp.lang.prolog:

> Hi,
>
> I have a doubt in SWI-Prolog. L and C are line and column respectively.
> I want that swi-prolog consider the numeric value of C-1. Is there any
> function to do this.
> the result of the query must be yes.
>
> q(9,8).
> p(L,C) :- q(L,C-1).
>
> ?-p(9,9)
> No

Try this:

q(9,8).
p(L,C):-
D is C - 1,
q(L,D).


?- p(9,9).

Yes

greetz
Wouter
--
http://www.ligezin.be/
.

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