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From: pereira@sri-unix.UUCP
Newsgroups: net.sources
Subject: Prolog library: not.hlp
Message-ID: <110@sri-unix.UUCP>
Date: Mon, 15-Aug-83 01:57:09 EDT
Article-I.D.: sri-unix.110
Posted: Mon Aug 15 01:57:09 1983
Date-Received: Thu, 11-Aug-83 13:15:11 EDT
Lines: 28

File: Util:Not.Hlp      Author: R.A.O'Keefe     Updated: 21 May 1983
 
#source.
The simple-minded not/1 lives in Util:Imisce.Pl.
Whenever you could use it, you aree strongly recommended to use \+ .
The suspicious not/1 lives in Util:Not.Pl.
 
#purpose.
The simple-minded not/1 was for compatibility with a long-dead version
of Dec-10 Prolog.  It has been retained because some other Prologs use
it.  However, it is always better to use \+ in Dec-10 Prolog, and it
is no worse in C Prolog.
 
There are problems with negated goals containing universally quantified
variables.  For example, if you write
        bachelor(X) :- \+married(X), male(X).
you will not be able to enumerate bachelors.  To help you detect such
errors, there is a suspicious version of not/1 which will report any
negated goals containing universally quantified variables.
 
#commands.
The source only defines one public predicate: not/1.
 
If it detects an error, not/1 will switch on tracing and enter a
break.
 
not/1 understands the existential quantifier ^ .  See the description
of bagof and setof in the Prolog manual to find out what that means.