NaN question

[Cephas]

How do i write an if statement that checks the results of a operation
to see if its nan (not a number) or not? *using g++, a linux complier*

I tried
double x;
if (x == nan)
{
code here
}

but nan isnt a built in defined varible.
I cant say:
if (x == 0)
because that means it holds a value of a number.

I am performing a complex mathimatical equation on diffrent variables
and need to create a if statement for the times that my equation
returns NaN.

Thanks!
-Cephas

 

[Thomas Wintschel]

How do i write an if statement that checks the results of a operation
to see if its nan (not a number) or not? *using g++, a linux complier*

I tried
double x;
if (x == nan)
{
code here
}

but nan isnt a built in defined varible.
I cant say:
if (x == 0)
because that means it holds a value of a number.

I am performing a complex mathimatical equation on diffrent variables
and need to create a if statement for the times that my equation
returns NaN.

Thanks!
-Cephas

there should be an isnan or isNaN function kicking around somewhere that you
can use to test a given value

Tom

 

[Sergei Zyablov]

How do i write an if statement that checks the results of a operation
to see if its nan (not a number) or not? *using g++, a linux complier*

//...
#include <math.h>
//...
if( isnan(0/0) )
cout << "0/0 = nan" << endl;
else
cout << "0/0 = " << (0/0) << endl;

Try
man isnan
for isinf() and finite().

 

[Ron Natalie]

In the C header math.h (or cmath in C++) there is a macro called isnan.