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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: How to check a Float for NaN
Date: Thu, 22 May 2014 10:24:35 +0100
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Date: 2014-05-22T10:24:35+01:00
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:

> On Thu, 22 May 2014 00:27:02 -0700 (PDT), jan.de.kruyf@gmail.com wrote:

>>       if Cos_Theta /= Cos_Theta then
>> 	 Gct.Trace (Debug_Str, "cos_theta is NaN******");
>>       else
>> 	 Gct.Trace (Debug_Str, "cos_theta : " & Long_Float'Image (Cos_Theta)); 
>>       end if;
>> 
>> gives this in the log:
>> 
>> [MATH3D.DEBUG] 1/372 cos_theta is NaN****** (2014-05-22 09:23:24.155)(loc: math3d.adb:129)
>> 
>> Hope it helps someone;
>
> You could simply use range check:
>
>    X in Long_Float'Range
>
> NaN is not a number and thus outside the range.

This would also return False for +/-Inf, so if the OP wants specifically
to check for NaN it wouldn't do. Can't think why they would, though.

GNAT says about "X in Long_Float'Range"
   inf.adb:10:60: warning: explicit membership test may be optimized away
   inf.adb:10:60: warning: use 'Valid attribute instead