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From: Bob Duff <bobduff@theworld.com>
Newsgroups: comp.lang.ada
Subject: Re: Ada reference manual rule for doubled parentheses around
 if_expression?
Date: Sat, 01 Aug 2015 09:42:14 -0400
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Date: 2015-08-01T09:42:14-04:00
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Stephen Leake <stephen_leake@stephe-leake.org> writes:

> Bob Duff <bobduff@theworld.com> writes:
>
>> Stephen Leake <stephen_leake@stephe-leake.org> writes:
>>
>>> 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.
>
> Thanks.

You're welcome.

> There's a similar rule for quantified expressions in 4.5.8(4).

Right.

> GNAT also accepts this:
>
>    function Expression_Function_1 (V : Integer) return Boolean
>      is (V = V and then True)
>           or else True;
>
> I think that's a bug, because there are no parens surrounding the
> entire expression. 

I agree that's a bug.  It doesn't seem to have anything to do with the
special rules about conditional/quantified expressions.  Or does it?

If you report this to report@adacore.com, it will get fixed.

- Bob