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

[Roberto Bagnara]

-------- Original Message --------
Subject: Re: Any Prolog language lawyer out there?
Date: 21 Oct 2004 10:19:55 GMT
From: Jan Wielemaker <jan at ct.xs4all.nl>
Reply-To: jan at nospam.swi.psy.uva.nl
Organization: SWI, University of Amsterdam
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> <1098274154.598785 at seven.kulnet.kuleuven.ac.be> <77bbf36a.0410210015.1db2726c at posting.google.com> <1098349684.287109 at seven.kulnet.kuleuven.ac.be>

In article <1098349684.287109 at seven.kulnet.kuleuven.ac.be>, Bart Demoen wrote:
> Mats Carlsson wrote:
> 
>>>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 should indeed have been more careful.
> 
> In principle, everything in the standard has a well-agreed upon meaning.
> In an attempt to ensure that, page 2 of the standard says in the 3th paragraph
> of section 3:
> 
> # Words and phrases not defined in this glossary are assumed
> # to have the meaning given in ISO 2382-15; if they do not
> # appear in ISO 2382-15, then they are assumed to have
> # their usual meaning.
> 
> "directly" is not defined in the ISO Prolog glossary (rest of section 3)
> 
> So we should check ISO 2382-15 ... I couldn't get hold of ISO 2382-15 (it is
> too expensive to acquire just to set this dispute) and if anybody has access
> to it and can check whether it defines "directly", please let us know.
> 
> If it isn't in ISO 2382-15, we must take the usual meaning of "directly".
> I think (apparently together with GNU Prolog and the makers of
> http://www.sju.edu/~jhodgson/prolog_proj/framed_spec.html) that in the context
> as it is used in the explanation of negative numbers, it means
> 
> 	"no spaces [or other stuff] in between"

That was also my line of thinking, but Mats is formally right.  Summarising
and highlighting the LAYOUT Mats refers to.

	<negative integer> ::= -, <integer>
	<integer> ::= <LAYOUT>, <integer token>
	<integer token> ::= <digit>+
	
The _immediately_ can only talk about the first rule above, so its meaning
is formally irrelevant as the second rules allows for layout :-(  Thats
why I went for a weaker form of reasoning claiming directly, only used
here, means something special.  I'm inclined to reject - 4, until someone
can, in addition to the standard, explain a rationale for these rules.

	Cheers --- Jan

-- 
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