Does the C++ Standard Library define pi?

Question

Does STL contain definition for pi (=3.14...)? Certainly, I can use old good M_PI, but it is non-standard and not cross-compiler compliant.

Also see [Best platform independent pi constant?](https://stackoverflow.com/q/21867617/1708801) — Shafik Yaghmour, Apr 11 '18 at 17:48

score 4 · Accepted Answer · answered Feb 19 '13 at 16:31

4

Boost.Math defines pi (and many other) mathematical constants to very high precision

#include <boost/math/constants.hpp>
long double pi = boost::math::constants::pi<long double>();

A full list is available here.

answered Feb 19 '13 at 16:31

Marshall Clow

If you need double precision then you can use the "template-free" constant like this: `double pi = boost::math::double_constants::pi;`. If you need several constants, then you may use a namespace alias like `namespace bmath = boost::math::double_constants;` and then refer to `bmath::pi`, `bmath::root_pi`, etc. – András Aszódi Jan 19 '14 at 13:55
2

In boost 1.57 the include is actually `` – void.pointer Jan 06 '15 at 20:21

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