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/*!
@file
Defines `boost::hana::power`.
@copyright Louis Dionne 2013-2017
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
*/
#ifndef BOOST_HANA_POWER_HPP
#define BOOST_HANA_POWER_HPP
#include <boost/hana/fwd/power.hpp>
#include <boost/hana/concept/integral_constant.hpp>
#include <boost/hana/concept/ring.hpp>
#include <boost/hana/config.hpp>
#include <boost/hana/core/dispatch.hpp>
#include <boost/hana/functional/iterate.hpp>
#include <boost/hana/functional/partial.hpp>
#include <boost/hana/mult.hpp>
#include <boost/hana/one.hpp>
#include <cstddef>
BOOST_HANA_NAMESPACE_BEGIN
//! @cond
template <typename X, typename N>
constexpr decltype(auto) power_t::operator()(X&& x, N const& n) const {
using R = typename hana::tag_of<X>::type;
using Power = BOOST_HANA_DISPATCH_IF(power_impl<R>,
hana::Ring<R>::value &&
hana::IntegralConstant<N>::value
);
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
static_assert(hana::Ring<R>::value,
"hana::power(x, n) requires 'x' to be in a Ring");
static_assert(hana::IntegralConstant<N>::value,
"hana::power(x, n) requires 'n' to be an IntegralConstant");
#endif
static_assert(N::value >= 0,
"hana::power(x, n) requires 'n' to be non-negative");
return Power::apply(static_cast<X&&>(x), n);
}
//! @endcond
template <typename R, bool condition>
struct power_impl<R, when<condition>> : default_ {
template <typename X, typename N>
static constexpr decltype(auto) apply(X&& x, N const&) {
constexpr std::size_t n = N::value;
return hana::iterate<n>(
hana::partial(hana::mult, static_cast<X&&>(x)),
hana::one<R>()
);
}
};
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_POWER_HPP
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