66 lines
2.0 KiB
C++
66 lines
2.0 KiB
C++
/*!
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@file
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Defines `boost::hana::power`.
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@copyright Louis Dionne 2013-2016
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_HANA_POWER_HPP
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#define BOOST_HANA_POWER_HPP
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#include <boost/hana/fwd/power.hpp>
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#include <boost/hana/concept/integral_constant.hpp>
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#include <boost/hana/concept/ring.hpp>
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/dispatch.hpp>
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#include <boost/hana/functional/iterate.hpp>
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#include <boost/hana/functional/partial.hpp>
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#include <boost/hana/mult.hpp>
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#include <boost/hana/one.hpp>
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#include <cstddef>
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BOOST_HANA_NAMESPACE_BEGIN
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//! @cond
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template <typename X, typename N>
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constexpr decltype(auto) power_t::operator()(X&& x, N const& n) const {
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using R = typename hana::tag_of<X>::type;
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using Power = BOOST_HANA_DISPATCH_IF(power_impl<R>,
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hana::Ring<R>::value &&
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hana::IntegralConstant<N>::value
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);
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#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
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static_assert(hana::Ring<R>::value,
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"hana::power(x, n) requires 'x' to be in a Ring");
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static_assert(hana::IntegralConstant<N>::value,
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"hana::power(x, n) requires 'n' to be an IntegralConstant");
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#endif
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static_assert(N::value >= 0,
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"hana::power(x, n) requires 'n' to be non-negative");
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return Power::apply(static_cast<X&&>(x), n);
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}
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//! @endcond
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template <typename R, bool condition>
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struct power_impl<R, when<condition>> : default_ {
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template <typename X, typename N>
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static constexpr decltype(auto) apply(X&& x, N const&) {
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constexpr std::size_t n = N::value;
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return hana::iterate<n>(
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hana::partial(hana::mult, static_cast<X&&>(x)),
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hana::one<R>()
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);
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}
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};
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_POWER_HPP
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