Path: utzoo!attcan!uunet!cs.utexas.edu!uwm.edu!rpi!batcomputer!munnari.oz.au!goanna!ok
From: ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe)
Newsgroups: comp.lang.prolog
Subject: Re: Standards question: behavior of arg/3
Message-ID: <4037@goanna.cs.rmit.oz.au>
Date: 22 Oct 90 03:22:50 GMT
References: <9888@bunny.GTE.COM> <3992@goanna.cs.rmit.oz.au> <1920@tuvie> <35019@cup.portal.com>
Organization: Comp Sci, RMIT, Melbourne, Australia
Lines: 15

In article <35019@cup.portal.com>, pgl@cup.portal.com (Peter G Ludemann) writes:
> Richard might not like the fact that IBM's arg/3 allows
> arg(0,f(a),f) -- that's easily fixed by using a delayed inequality:
>     wait:(N ==/ 0) & arg(N,F,X)

Ah, I see:  if N is already instantiated the N==/0 (what the dickens
does ==/ mean?) goal will fail, if N is not instantiated arg/3 will
generate the *bogus* incredibly meaningless N=0 solution which will
then be rejected.  Good one.

If someone really wants arg0/3, by all means let them have it, but
let it be called arg0/3, not arg/3.

-- 
Fear most of all to be in error.	-- Kierkegaard, quoting Socrates.