Hello, I have a little assembly routine that tells me if a float is infinite. Does such a routine exist to check whether a float is not a number? EDIT: I am programming under Windows XP Thanks :)

Quote:Original post by Floating
Hello,

I have a little assembly routine that tells me if a float is infinite. Does such a routine exist to check whether a float is not a number?
EDIT: I am programming under Windows XP

Thanks :)

bool isNan(float x) {    if(x == x)        return false;    return true;    //or return x != x;}

CM

Thanks for the quick reply :)

Just another little question: how come following code doesn't work?

if (number==std::numeric_limits<float>::infinity())
Beep(1000,1000);
if (number==std::numeric_limits<float>::quiet_NaN())
Beep(1000,1000);

_isnan(x)

?

Thank you for the replies.

And how can I use std::numeric_limits<float>::infinity() ?
Is it only meant to generate an infinite value or can I use it to check if my number is infinite too?

Quote:Original post by iMalc

Quote:Original post by Conner McCloud

bool isNan(float x) {    if(x == x)        return false;    return true;    //or return x != x;}

That's odd, that definately doesn't work for the nan produced by dividing zero by zero, which is the easiest way to produce a nan that I can think of. Are you sure that should work?

1/0 is infinity, not NaN. *edit: doh, zero/zero. Not sure on that point, let me check. *edit2: For me at least, isNaN(0.0/0.0) yields true. The format of that is fff8000000000000, which is a NaN according to the IEEE standard , so I don't see why it wouldn't work, although "cout &lt;&lt; 0.0/0.0" yields "-1.#IND". So…*shrug*.<br><br>floating: I'm less certain &#111;n this point, but I believe infinity is allowed to equal itself. A quick test program confirms that that appears to be the behavior. So you can just compare to numeric_limits&lt;double&gt;::infinity(), provided you're careful of sign, since you can have both a positive and a negative infinity, and they don't equal each other. <br><pre><br>bool isInf(float x)<br>{<br> return fabs(x) == numeric_limits&lt;double&gt;::infinity();<br>}</pre><br><br>In .NET2003, I can't get isnan to work with either math.h or cmath. The IDE does see _isnan, but it is declared in float.h. <br><br>CM