Chris@16: //   Boost pow.hpp header file
Chris@16: //   Computes a power with exponent known at compile-time
Chris@16: 
Chris@16: //  (C) Copyright Bruno Lalande 2008.
Chris@16: //  Distributed under the Boost Software License, Version 1.0.
Chris@16: //  (See accompanying file LICENSE_1_0.txt or copy at
Chris@16: //  http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: //  See http://www.boost.org for updates, documentation, and revision history.
Chris@16: 
Chris@16: 
Chris@16: #ifndef BOOST_MATH_POW_HPP
Chris@16: #define BOOST_MATH_POW_HPP
Chris@16: 
Chris@16: 
Chris@101: #include <boost/math/special_functions/math_fwd.hpp>
Chris@16: #include <boost/math/policies/policy.hpp>
Chris@16: #include <boost/math/policies/error_handling.hpp>
Chris@16: #include <boost/math/tools/promotion.hpp>
Chris@16: #include <boost/mpl/greater_equal.hpp>
Chris@16: 
Chris@16: 
Chris@16: namespace boost {
Chris@16: namespace math {
Chris@16: 
Chris@101: #ifdef BOOST_MSVC
Chris@101: #pragma warning(push)
Chris@101: #pragma warning(disable:4702) // Unreachable code, only triggered in release mode and /W4
Chris@101: #endif
Chris@16: 
Chris@16: namespace detail {
Chris@16: 
Chris@16: 
Chris@16: template <int N, int M = N%2>
Chris@16: struct positive_power
Chris@16: {
Chris@16:     template <typename T>
Chris@16:     static T result(T base)
Chris@16:     {
Chris@16:         T power = positive_power<N/2>::result(base);
Chris@16:         return power * power;
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: template <int N>
Chris@16: struct positive_power<N, 1>
Chris@16: {
Chris@16:     template <typename T>
Chris@16:     static T result(T base)
Chris@16:     {
Chris@16:         T power = positive_power<N/2>::result(base);
Chris@16:         return base * power * power;
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: template <>
Chris@16: struct positive_power<1, 1>
Chris@16: {
Chris@16:     template <typename T>
Chris@16:     static T result(T base){ return base; }
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: template <int N, bool>
Chris@16: struct power_if_positive
Chris@16: {
Chris@16:     template <typename T, class Policy>
Chris@16:     static T result(T base, const Policy&)
Chris@16:     { return positive_power<N>::result(base); }
Chris@16: };
Chris@16: 
Chris@16: template <int N>
Chris@16: struct power_if_positive<N, false>
Chris@16: {
Chris@16:     template <typename T, class Policy>
Chris@16:     static T result(T base, const Policy& policy)
Chris@16:     {
Chris@16:         if (base == 0)
Chris@16:         {
Chris@16:             return policies::raise_overflow_error<T>(
Chris@16:                        "boost::math::pow(%1%)",
Chris@16:                        "Attempted to compute a negative power of 0",
Chris@16:                        policy
Chris@16:                    );
Chris@16:         }
Chris@16: 
Chris@16:         return T(1) / positive_power<-N>::result(base);
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: template <>
Chris@16: struct power_if_positive<0, true>
Chris@16: {
Chris@16:     template <typename T, class Policy>
Chris@16:     static T result(T base, const Policy& policy)
Chris@16:     {
Chris@16:         if (base == 0)
Chris@16:         {
Chris@16:             return policies::raise_indeterminate_result_error<T>(
Chris@16:                        "boost::math::pow(%1%)",
Chris@16:                        "The result of pow<0>(%1%) is undetermined",
Chris@16:                        base,
Chris@16:                        T(1),
Chris@16:                        policy
Chris@16:                    );
Chris@16:         }
Chris@16: 
Chris@16:         return T(1);
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: template <int N>
Chris@16: struct select_power_if_positive
Chris@16: {
Chris@16:     typedef typename mpl::greater_equal<
Chris@16:                          mpl::int_<N>,
Chris@16:                          mpl::int_<0>
Chris@16:                      >::type is_positive;
Chris@16: 
Chris@16:     typedef power_if_positive<N, is_positive::value> type;
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: }  // namespace detail
Chris@16: 
Chris@16: 
Chris@16: template <int N, typename T, class Policy>
Chris@16: inline typename tools::promote_args<T>::type pow(T base, const Policy& policy)
Chris@16: { 
Chris@16:    typedef typename tools::promote_args<T>::type result_type;
Chris@16:    return detail::select_power_if_positive<N>::type::result(static_cast<result_type>(base), policy); 
Chris@16: }
Chris@16: 
Chris@16: 
Chris@16: template <int N, typename T>
Chris@16: inline typename tools::promote_args<T>::type pow(T base)
Chris@16: { return pow<N>(base, policies::policy<>()); }
Chris@16: 
Chris@101: #ifdef BOOST_MSVC
Chris@101: #pragma warning(pop)
Chris@101: #endif
Chris@16: 
Chris@16: }  // namespace math
Chris@16: }  // namespace boost
Chris@16: 
Chris@16: 
Chris@16: #endif