isnan

[Rotkiv]

In javascript i remember that there was a function called isnan that determined wether the information in quetion was 'not a number.' How does one determine this in C++?

[joe_bruin]

in c, everything is a number. whether the number representation is legal or meaningful is up to the programmer to decide.

[Valmont]

On Unix system, you'll have the isnan method at your disposal ( math.h ). You'll need to check for both infinity as well as not-a-number. Use a logical OR. That's a caveat!

- Take the square root of a negative number.
- Check for: isnan(MyNumber) || isinf(MyNumber)

Check out this:
http://math.nist.gov/tnt/index.html

Download that tool, since the C++ standard does not yet defined functions to classify NaN's. At least you'll have something to work with.

[Rotkiv]

cool, thank you very much.

[bdiamond]

isn't there also a function called 'isdigit()'? that you could use on each char

[frrossk]

Sure...isdigit(), isalpha(), etc..there are more function of this kind...check out http://msdn.microsoft.com/library/de..._.iswdigit.asp