Received-SPF: fail (google.com: domain of abnf-discuss-bounces@ietf.org does not designate 2001:1890:123a::1:1e as permitted sender) client-ip=2001:1890:123a::1:1e;
Date: Wed, 13 Jun 2012 11:57:46 +0100
From: Tony Finch <dot@dotat.at>
To: Paul Kyzivat <pkyzivat@alum.mit.edu>
In-Reply-To: <4FD79FAD.8040409@alum.mit.edu>
Message-ID: <alpine.LSU.2.00.1206131151160.10149@hermes-2.csi.cam.ac.uk>
References: <2CCD27F5-B8D5-4C51-A830-54E6E2676029@lineone.net>
	<4FD79FAD.8040409@alum.mit.edu>
User-Agent: Alpine 2.00 (LSU 1167 2008-08-23)
MIME-Version: 1.0
Cc: abnf-discuss@ietf.org
Subject: Re: [abnf-discuss] Unordered lists with specific cardinality
Precedence: list
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Sender: abnf-discuss-bounces@ietf.org
Errors-To: abnf-discuss-bounces@ietf.org

Paul Kyzivat <pkyzivat@alum.mit.edu> wrote:
>
> It would be nice to extend ABNF with some syntax to help with this. But no
> good syntax for this leaps into my mind.

This would make ABNF no longer straightforwardly translatable into other
BNF-alikes. I don't think it would be worth it.

An example from the C standard shows it is normal to deal with this kind
of problem with a constraint described in the text.


  6.7 Declarations

  Syntax

         declaration:
                 declaration-specifiers init-declarator-listopt ";"
         declaration-specifiers:
                 storage-class-specifier declaration-specifiersopt
                 type-specifier declaration-specifiersopt
                 type-qualifier declaration-specifiersopt
                 function-specifier declaration-specifiersopt
         init-declarator-list:
                 init-declarator
                 init-declarator-list "," init-declarator
         init-declarator:
                 declarator
                 declarator "=" initializer

  6.7.1 Storage-class specifiers

  Syntax

         storage-class-specifier:
                  "typedef"
                  "extern"
                  "static"
                  "auto"
                  "register"
  Constraints

  At most, one storage-class specifier may be given in the declaration
  specifiers in a declaration.


Tony.
-- 
f.anthony.n.finch  <dot@dotat.at>  http://dotat.at/
Humber, Thames, Dover, Wight, Portland, Plymouth: Variable 3 or 4, becoming
southeast 4 or 5 later in Plymouth. Slight or moderate. Rain or showers.
Moderate or good.
_______________________________________________
abnf-discuss mailing list
abnf-discuss@ietf.org
https://www.ietf.org/mailman/listinfo/abnf-discuss