MFC and std namespace-beginner question

7stud

I need to use the sqrt() function in in one of my functions in a Windows program using MFC. At the top of the file I put in these lines: #include <cmath> using std::sqrt; and I got this error: error C2653: 'std' : is not a class or namespace name Why doesn't the compiler recognize the std namespace?

Alexandru Savescu

It's odd that it does not work. As a workaround, use the C-standart function. #include <math.h> ... double x = sqrt (y); Best regards, Alexandru Savescu P.S. Interested in art? Visit this!

7stud

Thanks, I did that. I'm using VC++ 6.0 if that helps.

hiseldl

Try: #include <cmath> using namespace std; ... // use the sqrt func float x = sqrt(y); or you can just call the sqrt function without the "using" keyword: #include <cmath> ... // use the sqrt func float x = std::sqrt(y); HTH. David Hisel -- http://www.hisel.com/

7stud

I tried both of those, but as expected, I get the same error--my compiler does not recognize "std" as a namespace. My compiler does recognize "std" as a namespace for win32 console apps, but not this, my first win32 with MFC app attempting to use the std namespace.

Hosam Aly Mahmoud

The things I will say in this reply are MS Visual C++ 6.0 specific. I have not tried them on any other compiler. 7stud wrote: My compiler does recognize "std" as a namespace for win32 console apps You probably use #include <iostream>, which includes the std namespace. But, the cmath header file does not contain the std namespace. In fact, the following code is perfectly legal:

#include <cmath>
int main() {
double x = sqrt(5);
}

But this one is not:

#include <cmath>
using std::sqrt;

So you don't need to use the std namespace if you are going to use cmath in Visual C++ 6.0. Hope this helps.

Hosam Aly Mahmoud

7stud

Thanks for the explanation.

Hosam Aly Mahmoud

You're welcome.