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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: extended membership tests (branch)
Date: Thu, 31 Mar 2011 16:10:26 -0500
Organization: Jacob Sparre Andersen Research & Innovation
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Date: 2011-03-31T16:10:26-05:00
List-Id: <comp.lang.ada>

"Adam Beneschan" <adam@irvine.com> wrote in message 
news:247eef65-9ff3-4268-af73-e74d092c1e82@k10g2000prh.googlegroups.com...
On Mar 31, 9:28 am, Georg Bauhaus <rm.dash-bauh...@futureapps.de>
wrote:
>> for b in b1 in b1 .. b1 loop
>> null;
>> end loop;
>
>See AARM 3.5(3.a).  "for b in" has to be followed by either a subtype
>name, a 'Range attribute, or two "simple expressions" with .. between
>them.  In the last case, the bounds must be "simple expressions", not
>general expressions.  The syntax of simple_expressions doesn't allow
>membership tests (except in parentheses).  So the above is illegal.
>This rule has been there since Ada 95.

Right. The only incompatibility involved with this new feature is with case 
statements. A membership test now needs to be parenthesized, as it did in 
Ada 83, but Ada 95 and Ada 2005 allowed it not to be in parens.

   when X in Y => -- Illegal in Ada 83 and Ada 2012, legal in Ada 95 and Ada 
2005.
   when (X in Y) => -- OK everywhere.

The reason is that something like:
   when X in Y | Z =>
would be ambiguous without the parens.

Beyond that, the likelyhood of writing something like this is pretty small 
anyway (why write a case statement on type Boolean??).

                             Randy.


                                 -- Adam