1 // Boost pow.hpp header file
2 // Computes a power with exponent known at compile-time
4 // (C) Copyright Bruno Lalande 2008.
5 // Distributed under the Boost Software License, Version 1.0.
6 // (See accompanying file LICENSE_1_0.txt or copy at
7 // http://www.boost.org/LICENSE_1_0.txt)
9 // See http://www.boost.org for updates, documentation, and revision history.
12 #ifndef BOOST_MATH_POW_HPP
13 #define BOOST_MATH_POW_HPP
16 #include <boost/math/policies/policy.hpp>
17 #include <boost/math/policies/error_handling.hpp>
18 #include <boost/math/tools/promotion.hpp>
19 #include <boost/mpl/greater_equal.hpp>
29 template <int N, int M = N%2>
33 static T result(T base)
35 T power = positive_power<N/2>::result(base);
41 struct positive_power<N, 1>
44 static T result(T base)
46 T power = positive_power<N/2>::result(base);
47 return base * power * power;
52 struct positive_power<1, 1>
55 static T result(T base){ return base; }
59 template <int N, bool>
60 struct power_if_positive
62 template <typename T, class Policy>
63 static T result(T base, const Policy&)
64 { return positive_power<N>::result(base); }
68 struct power_if_positive<N, false>
70 template <typename T, class Policy>
71 static T result(T base, const Policy& policy)
75 return policies::raise_overflow_error<T>(
76 "boost::math::pow(%1%)",
77 "Attempted to compute a negative power of 0",
82 return T(1) / positive_power<-N>::result(base);
87 struct power_if_positive<0, true>
89 template <typename T, class Policy>
90 static T result(T base, const Policy& policy)
94 return policies::raise_indeterminate_result_error<T>(
95 "boost::math::pow(%1%)",
96 "The result of pow<0>(%1%) is undetermined",
109 struct select_power_if_positive
111 typedef typename mpl::greater_equal<
116 typedef power_if_positive<N, is_positive::value> type;
120 } // namespace detail
123 template <int N, typename T, class Policy>
124 inline typename tools::promote_args<T>::type pow(T base, const Policy& policy)
126 typedef typename tools::promote_args<T>::type result_type;
127 return detail::select_power_if_positive<N>::type::result(static_cast<result_type>(base), policy);
131 template <int N, typename T>
132 inline typename tools::promote_args<T>::type pow(T base)
133 { return pow<N>(base, policies::policy<>()); }