63e88f80
 Hu Chunming
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/*!
@file
Defines `boost::hana::repeat`.
Copyright Louis Dionne 2013-2022
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_REPEAT_HPP
#define BOOST_HANA_REPEAT_HPP
#include <boost/hana/fwd/repeat.hpp>
#include <boost/hana/concept/integral_constant.hpp>
#include <boost/hana/config.hpp>
#include <boost/hana/core/dispatch.hpp>
#include <cstddef>
#include <utility>
namespace boost { namespace hana {
template <typename I, bool condition>
struct repeat_impl<I, when<condition>> : default_ {
template <typename F, std::size_t ...i>
static constexpr void repeat_helper(F&& f, std::index_sequence<i...>) {
using Swallow = std::size_t[];
(void)Swallow{0, ((void)f(), i)...};
}
template <typename N, typename F>
static constexpr auto apply(N const&, F&& f) {
static_assert(N::value >= 0, "hana::repeat(n, f) requires 'n' to be non-negative");
constexpr std::size_t n = N::value;
repeat_helper(static_cast<F&&>(f), std::make_index_sequence<n>{});
}
};
//! @cond
template <typename N, typename F>
constexpr void repeat_t::operator()(N const& n, F&& f) const {
using I = typename hana::tag_of<N>::type;
using Repeat = BOOST_HANA_DISPATCH_IF(repeat_impl<I>,
hana::IntegralConstant<I>::value
);
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
static_assert(hana::IntegralConstant<I>::value,
"hana::repeat(n, f) requires 'n' to be an IntegralConstant");
#endif
return Repeat::apply(n, static_cast<F&&>(f));
}
//! @endcond
}} // end namespace boost::hana
#endif // !BOOST_HANA_REPEAT_HPP
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