Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!lll-crg!nike!sri-spam!parcvax!hplabs!tektronix!uw-beaver!ubc-vision!ubc-cs!andrews
From: andrews@ubc-cs.UUCP (Jamie Andrews)
Newsgroups: net.lang.prolog
Subject: Re: fixed points
Message-ID: <381@ubc-cs.UUCP>
Date: Tue, 2-Sep-86 13:04:41 EDT
Article-I.D.: ubc-cs.381
Posted: Tue Sep  2 13:04:41 1986
Date-Received: Wed, 3-Sep-86 21:10:34 EDT
References: <8608250740.AA00215@ucbvax.Berkeley.EDU> <177@zyx.UUCP>
Reply-To: andrews@ubc-cs.UUCP (Jamie Andrews)
Organization: UBC Department of Computer Science, Vancouver, B.C., Canada
Lines: 27

>In article <8608250740.AA00215@ucbvax.Berkeley.EDU>
> PGW@XX.LCS.MIT.EDU (Paul G. Weiss) writes:
>>Ideally, I would like to find a one-clause predicate fixed/1, with the
>>property that fixed(Term) is true of the Term which is the clause that
>>defines fixed/1.

In article <177@zyx.UUCP> bd@zyx.UUCP (Bjorn Danielsson) writes:
>I have found a solution, but it requires an extra predicate that interprets
>a "represented" clause and melts it into a lower level of representation.
>Using an extra predicate might seem like cheating, especially if you write
>something like:
>
>   fixed(X) :- cheat(X).   cheat((fixed(X) :- cheat(X))).

     Actually, the original query was framed so loosely that even this
program works:

fixed(X).

     I think Paul Weiss probably wanted to say "fixed(Term) is true ONLY
of Terms which are clauses defining a predicate extensionally identical
to fixed(Term)."  Can the people who proposed solutions prove that their
solutions have this property?

--Jamie.
...!seismo!ubc-vision!ubc-cs!andrews
"Two sapphires and a couple rows of pearls"