#include <cmath>
    double fabs( double arg );

The function fabs() returns the absolute value of arg.

C++ also provides the following overloaded forms:

    #include <cmath>
    float fabs( float arg ); // same as fabsf() in C99
    long double fabs( long double arg ); // same as fabsl() in C99

You can also use abs() instead of fabs() in C++, as it contains overloaded versions for it.

Related Topics: abs, fmod, labs