| // 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 |