-------- Original Message -------- Subject: Re: Any Prolog language lawyer out there? Date: 21 Oct 2004 01:12:22 -0700 From: matsc@sics.se (Mats Carlsson) Organization: http://groups.google.com Newsgroups: comp.lang.prolog References: 41750912.8040102@cs.unipr.it 1098196164.417498@seven.kulnet.kuleuven.ac.be slrncnaat8.jkn.jan@ct.xs4all.nl 87acuijutl.fsf@gondolin.bb.bawue.de 1098259920.942884@seven.kulnet.kuleuven.ac.be 1098274154.598785@seven.kulnet.kuleuven.ac.be

Bart Demoen bmd@cs.kuleuven.ac.be wrote in message news:1098274154.598785@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 corresponding negative constant"

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

That must be wishful thinking on your part. There is no such definition of "directly" in the document. I too have the standard document, from which I quote the relevant grammar rules:

6.3.1.2 Negative Numbers

term = name, integer ; term = name, float number ;

/* where the name must be '-' */

6.4 Tokens

name = [ layout text sequence ], name token ;

6.4.1 Layout text

layout text sequence = layout text, { layout text } ;

layout text = layout char | comment ;

6.4.2 Names

name token = letter digit token | graphic token | quoted token | semicolon token | cut token ;

letter digit token = small letter char, { alphanumeric char } ;

So clearly, there can be space, even comments, between the '-' and the digits. BTW, the same applies to [/*this atom*/] and {/*this atom*/}.

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

To the contrary, it should.

--Mats