Path: utzoo!attcan!uunet!munnari!otc!metro!basser!usage!ccadfa!cancol!jan
From: jan@cancol.oz (Jan Newmarch)
Newsgroups: comp.lang.prolog
Subject: Re: Quintus compatibles
Summary: Arity compatability
Message-ID: <123@cancol.oz>
Date: 13 Feb 89 04:36:00 GMT
References: <291@Intrepid.ece.ukans.edu> <8700001@iuvax>
Organization: Info. Sciences, Canberra Coll. of Adv. Ed.
Lines: 32


We have used Arity/Prolog for some years. The worst incompatability
is the if..then..else construct:

	ifthenelse(P,Q,R)
and
	ifthen(P,Q)
instead of (P->Q;R) and (P->Q). Unfortunately Arity have swiped the
operator -> for use in a case statement construct with the wrong
precedence for P->Q. The interpreter is ok - add this to the start of your
DEC-10 program:

	:- op(0,xfy, -> ).   % kill the operator
	:- op(1100,xfy, -> ). % bring it back with better precedence

	(P->Q;R) :- ifthenelse(P,Q,R).
	(P->Q)   :- ifthenelse(P,Q,fail). % ifthen(P,Q) succeeds if P fails

This does not work for the Arity/Prolog compiler, and you are best off
writing a translator from (P->Q) notation to that of Arity.

Most other things are fine, but you have to watch for little DEC-10
oddities like put("a") which Arity doesn't like.

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