// Boost pow.hpp header file | |
// Computes a power with exponent known at compile-time | |
// (C) Copyright Bruno Lalande 2008. | |
// Distributed under the Boost Software License, Version 1.0. | |
// (See accompanying file LICENSE_1_0.txt or copy at | |
// http://www.boost.org/LICENSE_1_0.txt) | |
// See http://www.boost.org for updates, documentation, and revision history. | |
#ifndef BOOST_MATH_POW_HPP | |
#define BOOST_MATH_POW_HPP | |
#include <boost/math/policies/policy.hpp> | |
#include <boost/math/policies/error_handling.hpp> | |
#include <boost/math/tools/promotion.hpp> | |
#include <boost/mpl/greater_equal.hpp> | |
namespace boost { | |
namespace math { | |
namespace detail { | |
template <int N, int M = N%2> | |
struct positive_power | |
{ | |
template <typename T> | |
static T result(T base) | |
{ | |
T power = positive_power<N/2>::result(base); | |
return power * power; | |
} | |
}; | |
template <int N> | |
struct positive_power<N, 1> | |
{ | |
template <typename T> | |
static T result(T base) | |
{ | |
T power = positive_power<N/2>::result(base); | |
return base * power * power; | |
} | |
}; | |
template <> | |
struct positive_power<1, 1> | |
{ | |
template <typename T> | |
static T result(T base){ return base; } | |
}; | |
template <int N, bool> | |
struct power_if_positive | |
{ | |
template <typename T, class Policy> | |
static T result(T base, const Policy&) | |
{ return positive_power<N>::result(base); } | |
}; | |
template <int N> | |
struct power_if_positive<N, false> | |
{ | |
template <typename T, class Policy> | |
static T result(T base, const Policy& policy) | |
{ | |
if (base == 0) | |
{ | |
return policies::raise_overflow_error<T>( | |
"boost::math::pow(%1%)", | |
"Attempted to compute a negative power of 0", | |
policy | |
); | |
} | |
return T(1) / positive_power<-N>::result(base); | |
} | |
}; | |
template <> | |
struct power_if_positive<0, true> | |
{ | |
template <typename T, class Policy> | |
static T result(T base, const Policy& policy) | |
{ | |
if (base == 0) | |
{ | |
return policies::raise_indeterminate_result_error<T>( | |
"boost::math::pow(%1%)", | |
"The result of pow<0>(%1%) is undetermined", | |
base, | |
T(1), | |
policy | |
); | |
} | |
return T(1); | |
} | |
}; | |
template <int N> | |
struct select_power_if_positive | |
{ | |
typedef typename mpl::greater_equal< | |
mpl::int_<N>, | |
mpl::int_<0> | |
>::type is_positive; | |
typedef power_if_positive<N, is_positive::value> type; | |
}; | |
} // namespace detail | |
template <int N, typename T, class Policy> | |
inline typename tools::promote_args<T>::type pow(T base, const Policy& policy) | |
{ | |
typedef typename tools::promote_args<T>::type result_type; | |
return detail::select_power_if_positive<N>::type::result(static_cast<result_type>(base), policy); | |
} | |
template <int N, typename T> | |
inline typename tools::promote_args<T>::type pow(T base) | |
{ return pow<N>(base, policies::policy<>()); } | |
} // namespace math | |
} // namespace boost | |
#endif |