Re: valid numbers

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Marcus Barnes (marcus++at++multigen.com)
Thu, 27 Mar 1997 13:28:24 -0800

On Mar 27, 8:11am, Bryan Wasileski wrote:
>
> I need to verify whether or not position and orientation data is valid;
> valid in the sense of being a valid number. Sometimes I receive data
> (via ethernet packets) that is NaN, "not a numer" and I need to make sure
> that it IS a valid floating point number before using it. Are there any
> routines already available that check for valid floating point
> representation?

You can learn about IEEE 754 Binary Floating-point Arithmetic from the math(3)
manual page. Also on IRIX 6.2 look at man isnan(3).

The tests you can use in your code are:

#include <math.h>
{
   float nan = HUGE_VAL + __infinity; /* like this to be NaN */

   if ( nan != nan ) printf( "found a NaN using !=" );
   if ( isnan( nan ) printf( "found a NaN using isnan()" );
}

Regards.

--
+ Marcus Barnes, Technical Staff        mailto:marcus++at++multigen.com +
+ Multigen Inc.                         http://www.multigen.com    +
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