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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: What is the warning about builtin-function on gcc-4.6.0 ?
Date: Sat, 26 Mar 2011 16:32:00 +0000
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Date: 2011-03-26T16:32:00+00:00
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Florian Weimer <fw@deneb.enyo.de> writes:

> * Simon Wright:
>
>> ytomino <aghia05@gmail.com> writes:
>>
>>> nn...then, there are no function to take infinity and NaN...
>>
>> 'Valid should do the trick.
>>
>>    FP_Value := 1.0 / 0.0;
>>    if FP_Value'Valid then
>>       --  it won't be
>
> This is a compiler bug.

I don't understand what you mean.

If the compiler doesn't raise an exception on division by zero (it's
allowed not to, and GNAT doesn't) it will (in this case) set the result
to +Inf, and 'Valid will return False.

That's for plain [Long_[Long_]]Float. If you've said

   subtype Real is Float range Float'Range;

you'll get a Constraint_Error on assignment of Inf or NaN to a Real.