Re: negotiation by failure- list operations

"ne0" wrote in message
news:1118600315.819949.155550@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> hi, what im trying to do is the following:
>
>
> delete1(X,L1,L2) that uses delete(X,L1,L2) but if X isnt in L1
> it should not throw NO - it should only throw YES
>
> i think its donesimilar to that predicate:
> different(X,Y) :- X=Y, !, true.
> different(X,Y).
>
> but how do i change my delete1 predicate that it throws YES if
> X isnt in L1 ?
>
> Can someone help me ?

Isn't this just a question of supplying a 'catch-all'
clause to delete1/3?

delete1(X,L1,L2) :-
delete(X,L1,L2).
delete1(_,_,_).

Now delete1/3 will always succeed, but whether it 'throws'
a YES may well depend on the Prolog system in use.

--
Mail sent to this email address is deleted unread
on the server. Please send replies to the newsgroup.


.