#include <boost/math/special_functions/trunc.hpp>

template <class T>
T trunc(const T& v);

template <class T, class Policy>
T trunc(const T& v, const Policy&);

template <class T>
int itrunc(const T& v);

template <class T, class Policy>
int itrunc(const T& v, const Policy&);

template <class T>
long ltrunc(const T& v);

template <class T, class Policy>
long ltrunc(const T& v, const Policy&);

template <class T>
long long lltrunc(const T& v);

template <class T, class Policy>
long long lltrunc(const T& v, const Policy&);

The trunc functions round their argument to the integer value, nearest to but no larger in magnitude than the argument.

For example itrunc(3.7) would return 3 and ltrunc(-4.6) would return -4.

If the argument v is either non-finite or else outside the range of the result type, then returns the result of rounding_error: by default this throws an instance of boost::math::rounding_error.