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From: eachus@spectre.mitre.org (Robert I. Eachus)
Subject: Re: C/C++ knocks the ....
Date: 1996/02/23
Message-ID: <EACHUS.96Feb23182705@spectre.mitre.org>#1/1
X-Deja-AN: 140855712
references: <4g2r2r$ded@stc06.ctd.ornl.gov> <JSA.96Feb19185926@organon.com>
organization: The Mitre Corp., Bedford, MA.
newsgroups: comp.lang.ada
Date: 1996-02-23T00:00:00+00:00
List-Id: <comp.lang.ada>

In article <Dn8JxK.MGK@world.std.com> bobduff@world.std.com (Robert A Duff) writes:

  > And it's an annoyance to compiler writer's, too.  Consider:
  >     X: Character := Character'('z');
  > where the string
  >     '('
  > is *not* a character literal.

  > Not a huge implementation problem, but still an annoyance.

   Once upon a time it was a huge implementation problem.  In Green
and, I think, Ada 80, there was no distiction between a type
conversion and a qualified expression.  When the syntax was first
changed to use the ' for qualified expressions, there
were cases where you had to do arbitrary lookahead
to determine whether or not the first ' started a character literal or
an attribute. A'B'('"','A','B','C',... is the canononical "horrible"
case.  In theory these cases still exist, but no compiler author is
that dumb.  You would have to have an implementation defined attribute
with a single character name, and that attribute would have to name a
subtype.

   Anyway, once there was a draft version of the RM where the rule was
that "an apostrophe following a name never begins a character literal,"
that rule became sacrosanct, and the tricky stuff in the scanner was
only used for error correction.

--

					Robert I. Eachus

with Standard_Disclaimer;
use  Standard_Disclaimer;
function Message (Text: in Clever_Ideas) return Better_Ideas is...