Re: Users-prolog Digest, Vol 86, Issue 4
Duncan Patton a Campbell <[email protected]>
| Newsgroups | gmane.comp.gnu.prolog.general |
|---|---|
| Organization | NeoText |
| Message-ID | <[email protected]> |
On Mon, 23 Aug 2010 12:00:22 -0400 [email protected] wrote: > > Hi all, > > I found a strange error on my gprolog coding, namely on the source: > > pred1([R-C-P|Ls], [R-C-P|Ls1]):- > memberchk(rel(_,X,Y), C), > memberchk(rel(_,Y,_), C), > nth(1,P,Z), > ... > I see no cut in this code snip, implying the potential for backtracking either here or further on. From the manual: " member(Element, List) succeeds if Element belongs to the List. This predicate is re-executable on backtracking and can be thus used to enumerate the elements of List. memberchk/2 is similar to member/2 but only succeeds once. " Dhu