how to use NAN 1

[zub44]

Hi

For the purposes of debugging a program, I would like to be able to ask whether a (double) variable has the value NAN (not a number). My question how do I check if x == NAN ?

For example:

#include <stdio.h>
#include <math.h>

int main()
{
double x;

[blue]x = sqrt(-1.0);[/blue]
printf("x = %f\n", x); /*prints "x = nan"*/

[red]if (x == NAN)[/red]
[blue]/*compiler doesn't know NAN or nan*/[/blue]
printf("x = NAN\n");

return 0;
}

Thanks
zub

 

[Salem]

       #include <math.h>
       int isnan(double value);

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