[PPL-devel] [Fwd: Re: Any Prolog language lawyer out there?]

[Roberto Bagnara]

-------- Original Message --------
Subject: Re: Any Prolog language lawyer out there?
Date: Wed, 20 Oct 2004 14:09:14 +0200
From: Bart Demoen <bmd at cs.kuleuven.ac.be>
Organization: KULeuvenNet
Newsgroups: comp.lang.prolog
References: <41750912.8040102 at cs.unipr.it> <1098196164.417498 at seven.kulnet.kuleuven.ac.be> <slrncnaat8.jkn.jan at ct.xs4all.nl> <87acuijutl.fsf at gondolin.bb.bawue.de> <1098259920.942884 at seven.kulnet.kuleuven.ac.be>

I wrote:

> Goal     : integer(- 4)
> Specification result :     Must fail
> 
> 
> 
> Goal     : integer(-4)
> Specification result :     Must succeed
> 
> 
> So it seems that the space between the - and the 4 is important.
> 
> I do not have the final copy of the standard, and although I do remember
> that there has been discussion about it, I do not remember the final 
> outcome,
> so can anybody check that's indeed what the standard says ?

I got hold of a standard ...

It says at the end of section that Jens was quoting from:

"A term which is the name - followed directly by a numeric constant,
denotes the cirresponding negative constant"

In the standard "directly" means something like "with no space in between".

That decides the issue I think: - 4 should not be read as a negative integer;
and -4 should be read as a negative integer.


Cheers

Bart Demoen

-- 
Prof. Roberto Bagnara
Computer Science Group
Department of Mathematics, University of Parma, Italy
http://www.cs.unipr.it/~bagnara/
mailto:bagnara at cs.unipr.it