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From: Robert Dewar <robert_dewar@my-deja.com>
Newsgroups: comp.lang.ada
Subject: RE: very specific question on Ada syntax
Date: Wed, 31 Jan 2001 06:02:03 GMT
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Date: 2001-01-31T06:02:03+00:00
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In article <mailman.980917762.19771.comp.lang.ada@ada.eu.org>,
  comp.lang.ada@ada.eu.org wrote:
> So please what is the most appropriate treatment (i.e.
> preventing extra checks  AFTER lexical analysis in most
> cases) for 'Access, 'Delta, 'Digits, 'Range? Tick
> Identifier or Tick Reserved_Word?

Either would work, someone has to list special cases here. In
GNAT we find it preferable not to distort the lexical rules of
the language (which clearly say that it is a reserved word),
and do the special tests in the parser, following the official
grammar in the RM.

But you could alter the lexical structure and alter the
grammar, and do the special checks in the lexical analyzer
if you want.

GNAT always attempts to keep its internal data structures as
close as possible to the formal definition. This has proved
a good choice since it means that the RM acts as a kind of
manual for the compiler.


>
> I would tend to say, it's better to put the extra check for
these four into the
> lexer and treat them as identifiers afterwards.
>
> >> Also here OpenToken will fail.]
> >
> >How? It should return access as a reserved keyword, surely
> >it does ...>
>
> Of course is does. So in the light of the above, it does not
fail.
>
>


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