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From: Jerry <lanceboyle@qwest.net>
Newsgroups: comp.lang.ada
Subject: Re: How to check a Float for NaN
Date: Fri, 9 May 2008 19:36:58 -0700 (PDT)
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Date: 2008-05-09T19:36:58-07:00
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On May 9, 12:49=A0pm, a...@anon.org (anon) wrote:
> =A0 --
> =A0 -- Nan is define to be greater than value of hex 16#FF000000#
> =A0 --
>
> =A0 function isNan ( N : Float ) return Boolean is
>
> =A0 =A0 =A0T : Long_Long_Integer :=3D Long_Long_Integer ( N ) ;
>
> =A0 =A0 begin
> =A0 =A0 =A0 if T > 16#FF000000# then
> =A0 =A0 =A0 =A0 return True ;
> =A0 =A0 =A0 else
> =A0 =A0 =A0 =A0 return False ;
> =A0 =A0 =A0 end if ;
> =A0 =A0 end ;
>
> In <3132e38d-18bb-4890-9cec-31056ac6e...@x19g2000prg.googlegroups.com>, Je=
rry <lancebo...@qwest.net> writes:
>
> >How would one check a Float or Long_Float if it has value NaN? The
> >only ways that I can come up with are to import a C function (isnan, I
> >think) or to write Long_Float'image(Some_Float) to a string and
> >examine the first three characters to see if they are "NaN" (and that
> >seems to be a GNAT implementation choice so might not be portable,
> >which is OK for my use).
>
> >Jerry

No offense to anon, but does this work? Does anyone know of a
reference for this definition of a NaN?

Also, wondering how one might detect an Inf.

It seems that there is enough information in this thread to begin
writing a little package to deal with some of these things.

Thanks for all the great tips, BTW.

Jerry