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From: lhe@sicsten.UUCP (Lars-Henrik Eriksson)
Newsgroups: net.lang.prolog
Subject: Re: Standard behavior?
Message-ID: <1163@sicsten.UUCP>
Date: Thu, 29-May-86 22:28:59 EDT
Article-I.D.: sicsten.1163
Posted: Thu May 29 22:28:59 1986
Date-Received: Sun, 1-Jun-86 07:33:55 EDT
References: <980@watdragon.UUCP> <253@ubc-cs.UUCP> <1021@watdragon.UUCP>
Reply-To: lhe@sicsten.UUCP (Lars-Henrik Eriksson)
Organization: Swedish Institute of Computer Science
Lines: 13

In article <1021@watdragon.UUCP> rggoebel@watdragon.UUCP writes:
>I don't believe that cut, var, and
>nonvar cannot be described logically, just because they aren't in Prolog
>implementations.

The reason why cut, var and nonvar cannot be "described logically" is that
they are non-logical (or meta-logical, if you wish) primitives, that is
primitives used to control the search for proofs.

The meaning of these primitives are dependent of the particular way an
implementation looks for proofs. With a different implementation you
could be forced to give a different meaning to cut, var and nonvar, or
even find that they couldn't be given any meaning at all.