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From: baldwin@rochester.ARPA (Douglas Baldwin)
Newsgroups: net.lang.prolog
Subject: "For All" in Prolog - Thanks
Message-ID: <21008@rochester.ARPA>
Date: Tue, 23-Sep-86 08:58:57 EDT
Article-I.D.: rocheste.21008
Posted: Tue Sep 23 08:58:57 1986
Date-Received: Tue, 23-Sep-86 22:02:16 EDT
Organization: U of Rochester, CS Dept., Rochester, NY
Lines: 14


        Thanks to everyone who answered my question a few
weeks ago about implementing "for all" in Prolog. The general
consensus was that
        forall X in S, Body
can be re-expressed as
        "there is no X in S such that Body doesn't hold"
which can be written in Prolog as
        not( In_S(X), not Body(X,...) )
(This is a mix of syntaxes from several Prologs, my original
description of the problem, etc., but the idea is clear I
hope.) This is clearly what I need. Special thanks to
Lee Naish, David Morley, Heiner Marxen and Steve Jones for
their discussions of this solution.