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From: Mario Amado Alves <maa@di.fct.unl.pt>
Newsgroups: comp.lang.ada
Subject: RE: very specific question on Ada syntax
Date: Mon, 29 Jan 2001 11:11:01 +0000 (WET)
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Date: 2001-01-29T11:11:01+00:00

"Restriction:
   no one-character attribute designators.
Conjecture:
   that restriction is necessary in order to tokenize a
   character_literal without semantic or syntactical analysis."
(Alves, revised)

"Since the truth of this depends on your arbitrary definition
of what is and what is not syntactical analysis [...]"
(Dewar)

Syntactical: ranging more than one lexical element. A lexer may be purely
morphological, i.e. based solely on the individual form of each element.
But that is rare. An Ada lexer must have some syntax---so the conjecture is
true!

"[..] properly written lexical analyzers for Ada solve this" (Dewar)

It is nice to know my personal lexer is "proper" apud Dewar :) Excerpt:

          when ''' =>
            if Previous_Kind = Identifier
            or (Previous_Kind = Delimiter and To_String(Previous_Form)=")")
            or Previous_Kind = Reserved_Word_All
            then
              Send(Delimiter, C);
            else
              State := Character_Literal_1;
            end if;

And I was surprised much hyped systems (OpenToken, AdaGIDE...) fail this!

Thanks.

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