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Re: How to check a Float for NaN

by Keith Thompson <kst-u@[EMAIL PROTECTED] > May 11, 2008 at 03:00 PM

anon@[EMAIL PROTECTED]
 (anon) writes:
> If you look at my first post on this topic and change the 16#FF000000# 
> to 16#7F000000# (typo, forgot to adjust for the sign-bit) its basically 
> what I have done except that I use a 64-bit sign integer instead of the 
> Unsigned_64.  In order to save coding time, did not want to add the
> extra statements. Plus, if it for a final (it that time of the year)
they 
> should be able add those lines.
[...]

You're using a value conversion.  This converts, for example, the
Float value 3.0 to the Long_Long_Integer value 3.  In your code, with
16#FF000000# changed to 16#7F000000#, this:

    T : Long_Long_Integer := Long_Long_Integer ( N ) ;
    ...
    if T > 16#7F000000# then
    ...

is essentially equivalent to this:

    if T > 2130706432.0 then

Try isNan(2.0E9) and isNan(3.0E9).

You need an Unchecked_Conversion.  You also need to make sure you
choose a floating-point and integer type of the same size, and to
allow for things like byte ordering (even if you're limiting the test
to systems that sup****t IEEE floating-point, which is probably a
reasonable restriction since other floating-point formats may not
sup****t NaNs at all).

-- 
Keith Thompson (The_Other_Keith) <kst-u@[EMAIL PROTECTED]
>
Nokia
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"
 




 35 Posts in Topic:
How to check a Float for NaN
Jerry <lanceboyle@[EMA  2008-04-30 03:27:51 
Re: How to check a Float for NaN
christoph.grein@[EMAIL PR  2008-04-30 03:47:54 
Re: How to check a Float for NaN
christoph.grein@[EMAIL PR  2008-04-30 03:50:15 
Re: How to check a Float for NaN
Adam Beneschan <adam@[  2008-04-30 08:02:05 
Re: How to check a Float for NaN
"Randy Brukardt"  2008-04-30 18:29:14 
Re: How to check a Float for NaN
"Stuart" <st  2008-05-01 09:04:11 
Re: How to check a Float for NaN
Jerry <lanceboyle@[EMA  2008-04-30 13:33:17 
Re: How to check a Float for NaN
Jerry <lanceboyle@[EMA  2008-04-30 13:36:21 
Re: How to check a Float for NaN
Adam Beneschan <adam@[  2008-04-30 14:53:54 
Re: How to check a Float for NaN
Adam Beneschan <adam@[  2008-04-30 16:23:13 
Re: How to check a Float for NaN
Adam Beneschan <adam@[  2008-04-30 18:00:21 
Re: How to check a Float for NaN
Keith Thompson <kst-u@  2008-05-01 12:52:16 
Re: How to check a Float for NaN
Jerry <lanceboyle@[EMA  2008-04-30 18:05:41 
Re: How to check a Float for NaN
Adam Beneschan <adam@[  2008-05-01 07:38:40 
Re: How to check a Float for NaN
"Stuart" <st  2008-05-01 18:14:09 
Re: How to check a Float for NaN
"Randy Brukardt"  2008-05-01 14:22:35 
Re: How to check a Float for NaN
Jerry <lanceboyle@[EMA  2008-05-01 16:57:26 
Re: How to check a Float for NaN
Jerry <lanceboyle@[EMA  2008-05-01 17:04:53 
Re: How to check a Float for NaN
Martin Krischik <krisc  2008-05-05 20:23:02 
Re: How to check a Float for NaN
anon@[EMAIL PROTECTED] (  2008-05-10 17:00:51 
Re: How to check a Float for NaN
Keith Thompson <kst-u@  2008-05-11 15:00:55 
Re: How to check a Float for NaN
anon@[EMAIL PROTECTED] (  2008-05-12 02:01:18 
Re: How to check a Float for NaN
Adam Beneschan <adam@[  2008-05-05 13:49:25 
Re: How to check a Float for NaN
Jerry <lanceboyle@[EMA  2008-05-06 11:09:56 
Re: How to check a Float for NaN
"Wiljan Derks"   2008-05-06 20:45:47 
Re: How to check a Float for NaN
Adam Beneschan <adam@[  2008-05-06 15:18:39 
Re: How to check a Float for NaN
"Randy Brukardt"  2008-05-07 17:56:57 
Re: How to check a Float for NaN
Stephen Leake <Stephe.  2008-05-09 03:24:21 
Re: How to check a Float for NaN
"Randy Brukardt"  2008-05-07 17:56:57 
Re: How to check a Float for NaN
Adam Beneschan <adam@[  2008-05-07 16:20:55 
Re: How to check a Float for NaN
anon@[EMAIL PROTECTED] (  2008-05-09 19:49:50 
Re: How to check a Float for NaN
Jerry <lanceboyle@[EMA  2008-05-09 19:36:58 
Re: How to check a Float for NaN
anon@[EMAIL PROTECTED] (  2008-05-10 03:53:54 
Re: How to check a Float for NaN
Georg Bauhaus <see.rep  2008-05-10 10:05:33 
Re: How to check a Float for NaN
christoph.grein@[EMAIL PR  2008-05-09 23:24:48 

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