Path: utzoo!mnetor!uunet!husc6!sri-unix!quintus!ok
From: ok@quintus.UUCP (Richard A. O'Keefe)
Newsgroups: comp.lang.prolog
Subject: Re: mine embarrassingly simple problem
Message-ID: <764@cresswell.quintus.UUCP>
Date: 12 Mar 88 00:23:09 GMT
References: <500@taux01.UUCP>
Organization: Quintus Computer Systems, Mountain View, CA
Lines: 21

In article <500@taux01.UUCP>, shahaf@taux01.UUCP (Shahaf Moshe) writes:
> Can someone help me in the following: In translation from WATERLOO 
> to Quintus code I need {an ancestral cut}.

(1) A predicate which "searches through the ancestors exactly as for
    ancestor and retry" is a rather hard thing to provide in a system
    which does last call optimisation, the whole point of which is to
    ensure that as many ancestors as possible are completely forgotten
    as soon as possible.  Quintus Prolog does not provide 'retry' either.

(2) We are currently putting some rather nice things into Quintus Prolog
    which I don't think we could implement at all if we supported
    ancestral cuts.
    
(3) Check to see whether your site has a support contract with Quintus.
    We *may* be able to advise you how to write your program so that
    it doesn't need ancestral cuts.

(4) Could you tell this newsgroup more about your program?  It would be
    very interesting to hear of something that ancestral cuts were
    needed for.  (They _aren't_ needed for interpreting Prolog!)