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From: rb@cci632.UUCP (Rex Ballard)
Newsgroups: net.lang.prolog
Subject: Logical? (Re: Cut, var, nonvar, and Goebel's stardom
Message-ID: <169@cci632.UUCP>
Date: Wed, 2-Jul-86 13:03:32 EDT
Article-I.D.: cci632.169
Posted: Wed Jul  2 13:03:32 1986
Date-Received: Fri, 4-Jul-86 07:45:53 EDT
References: <6500005@uicsl> <29700028@uiucdcs> <270@ubc-cs.UUCP> <3830@utah-cs.UUCP>
Reply-To: rb@ccird1.UUCP (Rex Ballard)
Organization: CCI, Rochester Development, Rochester, NY
Lines: 28
Summary: Instantiation

In article <3830@utah-cs.UUCP> u-reddy@utah-cs.UUCP (Uday U-reddy) writes:
>In article <270@ubc-cs.UUCP> andrews@ubc-cs.UUCP (Jamie Andrews) writes:
>>     Well, as far as cut is concerned:  it's fairly easy to explain it
>>"logically", though not as a predicate or a goal, which is what I assume
>>you meant.
>>--Jamie.
>
>Sorry Jamie, I fail to understand this completely.  We had lengthy
>discussions, in Prolog digest last year, on what is logical and what isn't.
>But, to cut (!) the long story short, something is logical if it has a
>logical value, like "true", or "false", or even nonstandard logical values
>like "neither true nor false" or "both true and false" or whatever. 
>Further, the logical value of any logical thing should be preserved under
>instantiation.
>
>Now, I am not sure if what you are saying has anything to do with the
>logical-ness of these constructs.
>
>Uday Reddy

Now I'm a little confused.  Aren't any goals which refer to uninstantiated
variables, which are later instantiated, potentially both true and false?
I normally think of a cut symbol as an uninstantiated variable that gets
instantiated to false.  I'm only a novice at this, but it at least helps
me to understand it better.  Ignorance is bliss :-).

Prolog is quickly becoming one of my favorite languages.
	Rex B.