I think I have found a bug in list processing

phi16 <[email protected]> Fri, 30 Mar 2012 00:24:22 +0900

Newsgroups	gmane.comp.gnu.prolog.bugs
Message-ID	<CAAG-i+jCcjKsXhj9=t3RyLhF-qR9=t+3a84fy+q2qXdH2jeoQg@mail.gmail.com>

I think the following dialogue is a bug:


| ?- member(3,X),member(2,X),member(3,X).

X = [3,2|_] ? ;

X = [3,2,3|_] ? ;

X = [3|_] ? ;

X = [3,3|_] ? ;

X = [3,_,3|_] ? ;

X = [3,_,_,3|_] ? ;

X = [3,_,_,_,3|_] ?


The input tells the list named X must contain 2.
But the 3rd output shows there is possible that X does not contain 2.

Thank you for viewing.