[c++] Pi Constant

How to use the PI constant in C++:

Ways:

1.

On some platforms you might need to

#define _USE_MATH_DEFINES

and then

M_PI

is your friend. Check for more. Taken from my math. h:

/* Define _USE_MATH_DEFINES before including math.h to expose these macro
* definitions for common math constants. These are placed under an #ifdef
* since these commonly-defined names are not part of the C/C++ standards.
*/


2.

Pi can be calculated as atan(1)*4. You could calculate the value this way and cache it


3.

const double pi = boost::math::constants::pi<double>();