From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,5df086f5b450f5c4
X-Google-Attributes: gid103376,public
X-Google-ArrivalTime: 2001-05-08 23:17:28 PST
From: "Martin Dowie" <martin.dowie@nospam.baesystems.com>
Newsgroups: comp.lang.ada
References: <3af1541f$1@pull.gecm.com> <uk83yv1su.fsf@gsfc.nasa.gov>
 <99iI6.18964$Kt2.2053818@news6-win.server.ntlworld.com>
 <3AF80887.F8942BE3@averstar.com>
Subject: Re: Ada95 BNF
Date: Wed, 9 May 2001 07:18:53 +0100
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 5.00.2314.1300
X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2314.1300
NNTP-Posting-Host: sg2c11210.dsge.edinbr.gmav.gecm.com
Message-ID: <3af8ded6$1@pull.gecm.com>
X-Trace: 9 May 2001 07:08:22 GMT, sg2c11210.dsge.edinbr.gmav.gecm.com
Path: 
 newsfeed.google.com!newsfeed.stanford.edu!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!dispose.news.demon.net!demon!btnet-peer0!btnet-feed5!btnet!newreader.ukcore.bt.net!pull.gecm.com!sg2c11210.dsge.edinbr.gmav.gecm.com
Xref: newsfeed.google.com comp.lang.ada:7353
Date: 2001-05-09T07:18:53+01:00
List-Id: <comp.lang.ada>

Fair enough, but I still thnk it is strange that it
wasn't defined along the lines of:

defining_program_unit_name ::=
  [ parent_unit_name "." ] defining_identifier

parent_unit_name ::=
  identifier

given that "identifier" already exists and can be
navigated to through the existing definitions in
about 2 clicks and by-passing all the 'invalid'
options anyway...

:-)


Tucker Taft <stt@averstar.com> wrote in message
news:3AF80887.F8942BE3@averstar.com...
> Martin Dowie wrote:
> >
> > Ok... this seems a little strange to me - but if those are the rules!
:-)
> >
> > Is it really that hard to come up with a BNF that does actually match
> > what the language does allow?
>
> In many cases it is preferable to make the BNF somewhat
> "looser" than the "official" grammar, and then do the
> checking as part of semantic checking, because the errors
> tend to be handled a bit more gracefully.  In addition,
> in Ada, there are constructs which look identical
> syntactically but which are distinct semantically, such
> as a type conversion and an array indexing.  The grammar
> in the LRM distinguishes these, whereas the grammar used
> for an LR parser can't, since an LR parser requires that
> the grammar be context-free (i.e. independent of the
> "meaning" of particular identifiers).
>
> --
> -Tucker Taft   stt@avercom.net   http://www.averstar.com/~stt/
> Chief Technology Officer, AverCom Corporation (A Titan Company)
> Burlington, MA  USA (AverCom was formerly the Commercial Division of
AverStar:
> http://www.averstar.com/services/ebusiness_applications.html)