75 lines
2.4 KiB
C++
75 lines
2.4 KiB
C++
/*!
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@file
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Defines `boost::hana::replicate`.
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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_REPLICATE_HPP
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#define BOOST_HANA_REPLICATE_HPP
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#include <boost/hana/fwd/replicate.hpp>
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#include <boost/hana/concept/integral_constant.hpp>
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#include <boost/hana/concept/monad_plus.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/core/make.hpp>
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#include <boost/hana/cycle.hpp>
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#include <boost/hana/lift.hpp>
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#include <cstddef>
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#include <utility>
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BOOST_HANA_NAMESPACE_BEGIN
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template <typename M>
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struct replicate_t {
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#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
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static_assert(hana::MonadPlus<M>::value,
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"hana::replicate<M>(x, n) requires 'M' to be a MonadPlus");
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#endif
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template <typename X, typename N>
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constexpr auto operator()(X&& x, N const& n) const {
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using Replicate = BOOST_HANA_DISPATCH_IF(replicate_impl<M>,
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hana::MonadPlus<M>::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::IntegralConstant<N>::value,
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"hana::replicate<M>(x, n) requires 'n' to be an IntegralConstant");
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#endif
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return Replicate::apply(static_cast<X&&>(x), n);
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}
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};
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template <typename M, bool condition>
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struct replicate_impl<M, when<condition>> : default_ {
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template <typename X, typename N>
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static constexpr auto apply(X&& x, N const& n) {
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return hana::cycle(hana::lift<M>(static_cast<X&&>(x)), n);
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}
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};
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template <typename S>
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struct replicate_impl<S, when<Sequence<S>::value>> {
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template <typename X, std::size_t ...i>
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static constexpr auto replicate_helper(X&& x, std::index_sequence<i...>)
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{ return hana::make<S>(((void)i, x)...); }
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template <typename X, typename N>
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static constexpr auto apply(X&& x, N const&) {
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constexpr std::size_t n = N::value;
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return replicate_helper(static_cast<X&&>(x),
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std::make_index_sequence<n>{});
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}
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};
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_REPLICATE_HPP
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