id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
13591	maybe a bug in math::constants library	seanxnie@…	John Maddock	"The following templated code will generate incorrect result in visual studio community 2017:

{{{
#include<iostream>
#include<boost/math/constants/constants.hpp>

// convienent defination of math constants
template<typename T> const T pi = boost::math::constants::pi<T>(); // PI
template<typename T> const T two_pi = boost::math::constants::two_pi<T>(); // 2*PI

// physical constants
template<typename T> const T mu_0 = 4.0*pi<T>*1.0e-4; // permeability of free space in H / km
int main()
{
	using T = double;
	auto w = two_pi<T> * 0.01;
	//auto t1 = pi<T>;
	auto t2 = mu_0<T>;
	std::cout<<""omega=""<<w<<std::endl;
	std::cout<<""mu_0=""<<t2<<std::endl;
	system(""pause"");

	return 0;
}

}}}

In VS2017, mu_0 will be 0.000. However, if I uncomment 
{{{
auto t1 = pi<T>
}}} 
in main, the result is correct. This problem does not happen when compiled with gcc 8.1 in Manjaro Linux. The boost library version is 1.67.0
"	Bugs	closed	Boost 1.67.0	math	Boost 1.67.0	Problem	obsolete