Article View: comp.lang.prolog
Article #200Re: To J.W. Lloyd (Foundations of Logic Programming)
From: Fernando Pereira
Date: Tue, 14 Apr 1992 21:31
Date: Tue, 14 Apr 1992 21:31
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1067 bytes
In article <3716@tuegate.tue.nl> wsbusup4@urc.tue.nl writes: >[...] >that _it_is_easy_to_show_that ~q is a logical consequence of comp(P) where >program P is: > > q :- ~r > r :- p > r :- ~p > p :- p > >We have tried to to this in our class, but with no result. Well, the completion of P is (1) q iff ~r. (2) r iff (p or ~p). (3) p iff p Since p or ~p is a tautology (in classical logic), r is true by (2) and thus q is false by (1), which means that ~q is true. Fernando Pereira 2D-447, AT&T Bell Laboratories 600 Mountain Ave, PO Box 636 Murray Hill, NJ 07974-0636 pereira@research.att.com
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arc1-ca.pugleaf.net!sparky!uunet!zaphod.mps.ohio-state.edu!pacific.mps.ohio-state.edu!linac!att!att!dptg!ulysses!andante!alice!pereiraReferences:
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Path: arc1-ca.pugleaf.net!sparky!uunet!zaphod.mps.ohio-state.edu!pacific.mps.ohio-state.edu!linac!att!att!dptg!ulysses!andante!alice!pereira From: pereira@alice.att.com (Fernando Pereira) Newsgroups: comp.lang.prolog Subject: Re: To J.W. Lloyd (Foundations of Logic Programming) Message-ID: <22576@alice.att.com> Date: 14 Apr 92 21:31:11 GMT References: <3716@tuegate.tue.nl> Reply-To: pereira@alice.UUCP () Organization: AT&T, Bell Labs Lines: 25