#include <boost/math/special_functions/bessel.hpp> #include <iostream> (...) double v = 5.0/3.0; /* an order of Bessel function */ double x = 2.5; /* an argument of bessel function */ double r; /* will contain a value */ r = boost::math::cyl_bessel_k(v, x); std::cout<<r<<std::endl;

Just in case someone is interested what is a modified Bessel function, this is an integral representation of Bessel funtion of order

*v*: