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From: cds@duke.UUCP (Craig D. Singer)
Newsgroups: net.lang.prolog
Subject: Re: Standard behavior?
Message-ID: <7233@duke.UUCP>
Date: Mon, 12-May-86 08:46:30 EDT
Article-I.D.: duke.7233
Posted: Mon May 12 08:46:30 1986
Date-Received: Tue, 13-May-86 19:28:35 EDT
References: <6500005@uicsl>
Reply-To: cds@duke.UUCP (Craig D. Singer)
Organization: Duke University
Lines: 22

In article <6500005@uicsl> gooley@uicsl.UUCP writes:
>
>Consider the following trivial predicate:
>
>a([]).
>a(_).
>
>Given the query :-a([]). , C-Prolog finds one match and UNSW Prolog finds two.
>Which is standard behavior?  How do other implementations behave?

I do not have the authority to say which is "standard" behavior, if by that
you mean which is found more commonly in implementations.  However, any book
on "vanilla" Prolog will tell you that "_" matches to anything, including a
null list, so I would indeed be annoyed by C-Prolog if it did not find two
matches.  Anybody disagree?
-- 
 

Craig D. Singer, Dept. of Computer Science, Duke University
Durham, NC 27706-2591.  Phone (919) 684-5110  (ext.20)
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