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// 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/special_functions/math_fwd.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 {
#ifdef BOOST_MSVC
#pragma warning(push)
#pragma warning(disable:4702) // Unreachable code, only triggered in release mode and /W4
#endif
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<>()); }
#ifdef BOOST_MSVC
#pragma warning(pop)
#endif
} // namespace math
} // namespace boost
#endif
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