boost/hana/replicate.hpp

0001 /*!
0002 @file
0003 Defines `boost::hana::replicate`.
0004
0005 Copyright Louis Dionne 2013-2022
0006 Distributed under the Boost Software License, Version 1.0.
0007 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
0008  */
0009
0010 #ifndef BOOST_HANA_REPLICATE_HPP
0011 #define BOOST_HANA_REPLICATE_HPP
0012
0013 #include <boost/hana/fwd/replicate.hpp>
0014
0015 #include <boost/hana/concept/integral_constant.hpp>
0016 #include <boost/hana/concept/monad_plus.hpp>
0017 #include <boost/hana/config.hpp>
0018 #include <boost/hana/core/dispatch.hpp>
0019 #include <boost/hana/core/make.hpp>
0020 #include <boost/hana/cycle.hpp>
0021 #include <boost/hana/lift.hpp>
0022
0023 #include <cstddef>
0024 #include <utility>
0025
0026
0027 namespace boost { namespace hana {
0028     //! @cond
0029     template <typename M>
0030     template <typename X, typename N>
0031     constexpr auto replicate_t<M>::operator()(X&& x, N const& n) const {
0032         using Replicate = BOOST_HANA_DISPATCH_IF(replicate_impl<M>,
0033             hana::MonadPlus<M>::value &&
0034             hana::IntegralConstant<N>::value
0035         );
0036
0037     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
0038         static_assert(hana::MonadPlus<M>::value,
0039         "hana::replicate<M>(x, n) requires 'M' to be a MonadPlus");
0040
0041         static_assert(hana::IntegralConstant<N>::value,
0042         "hana::replicate<M>(x, n) requires 'n' to be an IntegralConstant");
0043     #endif
0044
0045         return Replicate::apply(static_cast<X&&>(x), n);
0046     }
0047     //! @endcond
0048
0049     template <typename M, bool condition>
0050     struct replicate_impl<M, when<condition>> : default_ {
0051         template <typename X, typename N>
0052         static constexpr auto apply(X&& x, N const& n) {
0053             return hana::cycle(hana::lift<M>(static_cast<X&&>(x)), n);
0054         }
0055     };
0056
0057     template <typename S>
0058     struct replicate_impl<S, when<Sequence<S>::value>> {
0059         template <typename X, std::size_t ...i>
0060         static constexpr auto replicate_helper(X&& x, std::index_sequence<i...>)
0061         { return hana::make<S>(((void)i, x)...); }
0062
0063         template <typename X, typename N>
0064         static constexpr auto apply(X&& x, N const&) {
0065             constexpr std::size_t n = N::value;
0066             return replicate_helper(static_cast<X&&>(x),
0067                                     std::make_index_sequence<n>{});
0068         }
0069     };
0070 }} // end namespace boost::hana
0071
0072 #endif // !BOOST_HANA_REPLICATE_HPP