1/*!
2@file
3Defines `boost::hana::power`.
4
5Copyright Louis Dionne 2013-2022
6Distributed under the Boost Software License, Version 1.0.
7(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
8 */
9
10#ifndef BOOST_HANA_POWER_HPP
11#define BOOST_HANA_POWER_HPP
12
13#include <boost/hana/fwd/power.hpp>
14
15#include <boost/hana/concept/integral_constant.hpp>
16#include <boost/hana/concept/ring.hpp>
17#include <boost/hana/config.hpp>
18#include <boost/hana/core/dispatch.hpp>
19#include <boost/hana/functional/iterate.hpp>
20#include <boost/hana/functional/partial.hpp>
21#include <boost/hana/mult.hpp>
22#include <boost/hana/one.hpp>
23
24#include <cstddef>
25
26
27namespace boost { namespace hana {
28 //! @cond
29 template <typename X, typename N>
30 constexpr decltype(auto) power_t::operator()(X&& x, N const& n) const {
31 using R = typename hana::tag_of<X>::type;
32 using Power = BOOST_HANA_DISPATCH_IF(power_impl<R>,
33 hana::Ring<R>::value &&
34 hana::IntegralConstant<N>::value
35 );
36
37 #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
38 static_assert(hana::Ring<R>::value,
39 "hana::power(x, n) requires 'x' to be in a Ring");
40
41 static_assert(hana::IntegralConstant<N>::value,
42 "hana::power(x, n) requires 'n' to be an IntegralConstant");
43 #endif
44
45 static_assert(N::value >= 0,
46 "hana::power(x, n) requires 'n' to be non-negative");
47
48 return Power::apply(static_cast<X&&>(x), n);
49 }
50 //! @endcond
51
52 template <typename R, bool condition>
53 struct power_impl<R, when<condition>> : default_ {
54 template <typename X, typename N>
55 static constexpr decltype(auto) apply(X&& x, N const&) {
56 constexpr std::size_t n = N::value;
57 return hana::iterate<n>(
58 hana::partial(hana::mult, static_cast<X&&>(x)),
59 hana::one<R>()
60 );
61 }
62 };
63}} // end namespace boost::hana
64
65#endif // !BOOST_HANA_POWER_HPP
66

source code of boost/libs/hana/include/boost/hana/power.hpp