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.
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Deduplicator
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Nick
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1Nope. But you can use `acos(-1.0)` or something similar – Bartek Banachewicz Feb 19 '13 at 09:31
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Also see [Best platform independent pi constant?](https://stackoverflow.com/q/21867617/1708801) – Shafik Yaghmour Apr 11 '18 at 17:48
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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.
Marshall Clow
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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. – Laryx Decidua Jan 19 '14 at 13:55
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