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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Ada reference manual rule for doubled parentheses around
 if_expression?
Date: Sat, 01 Aug 2015 08:36:35 +0100
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Date: 2015-08-01T08:36:35+01:00
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Bob Duff <bobduff@theworld.com> writes:

> Stephen Leake <stephen_leake@stephe-leake.org> writes:
>
>> A question recently came up on the Emacs ada-mode list; my Emacs
>> ada-mode parser rejects this if_expression in an association list:
>>
>>    Tmp : Boolean := Id (if True then True else True);
>>
>> but accepts this:
>>
>>    Tmp : Boolean := Id ((if True then True else True));
>>
>> I remember seeing some rule in the Ada reference manual that says the
>> doubled parens are not needed here. But now I can't find the rule,
>> and I don't want to edit my grammar without a reference.
>>
>> Anyone know where that rule is? or what to search for?
>
> 4.5.7(7).  This is a syntax rule, despite not being written in BNF.  I
> suggest you read the AARM annotations.

The question to which Stephe refers also shows

   function F2 (V : Integer) return Boolean
   is (True and then True)
      or else True;

which GNAT accepts but probably shouldn't? the parens in ARM 6.8(2)[1]
wrap the whole expression.

[1] http://www.ada-auth.org/standards/12rm/html/RM-6-8.html#p2