v3/functional/compose.hpp

0001 /// \file
0002 // Range v3 library
0003 //
0004 //  Copyright Eric Niebler 2013-present
0005 //
0006 //  Use, modification and distribution is subject to the
0007 //  Boost Software License, Version 1.0. (See accompanying
0008 //  file LICENSE_1_0.txt or copy at
0009 //  http://www.boost.org/LICENSE_1_0.txt)
0010 //
0011 // Project home: https://github.com/ericniebler/range-v3
0012 //
0013 #ifndef RANGES_V3_FUNCTIONAL_COMPOSE_HPP
0014 #define RANGES_V3_FUNCTIONAL_COMPOSE_HPP
0015
0016 #include <type_traits>
0017 #include <utility>
0018
0019 #include <concepts/concepts.hpp>
0020
0021 #include <range/v3/detail/config.hpp>
0022 #include <range/v3/functional/invoke.hpp>
0023 #include <range/v3/utility/static_const.hpp>
0024
0025 #include <range/v3/detail/prologue.hpp>
0026
0027 namespace ranges
0028 {
0029     /// \addtogroup group-functional
0030     /// @{
0031     template<typename Second, typename First>
0032     struct composed
0033     {
0034     private:
0035         RANGES_NO_UNIQUE_ADDRESS
0036         First first_;
0037         RANGES_NO_UNIQUE_ADDRESS
0038         Second second_;
0039
0040         // clang-format off
0041         template<typename A, typename B, typename... Ts>
0042         static constexpr auto //
0043         CPP_auto_fun(do_)(A &&a, B &&b, std::false_type, Ts &&... ts)
0044         (
0045             return invoke((B &&) b, invoke((A &&) a, (Ts &&) ts...))
0046         )
0047         template<typename A, typename B, typename... Ts>
0048         static constexpr auto CPP_auto_fun(do_)(A &&a, B &&b, std::true_type, Ts &&... ts)
0049         (
0050             return (invoke((A &&) a, (Ts &&) ts...), invoke((B &&) b))
0051         )
0052     public:
0053         composed() = default;
0054         // clang-format on
0055         constexpr composed(Second second, First first)
0056           : first_(std::move(first))
0057           , second_(std::move(second))
0058         {}
0059         // clang-format off
0060         template<typename... Ts>
0061         constexpr auto CPP_auto_fun(operator())(Ts &&... ts)(mutable &)
0062         (
0063             return composed::do_(first_,
0064                                  second_,
0065                                  std::is_void<invoke_result_t<First &, Ts...>>{},
0066                                  (Ts &&) ts...)
0067         )
0068         template<typename... Ts>
0069         constexpr auto CPP_auto_fun(operator())(Ts &&... ts)(const &)
0070         (
0071             return composed::do_((First const &)first_,
0072                                  (Second const &)second_,
0073                                  std::is_void<invoke_result_t<First const &, Ts...>>{},
0074                                  (Ts &&) ts...)
0075         )
0076         template<typename... Ts>
0077         constexpr auto CPP_auto_fun(operator())(Ts &&... ts)(mutable &&)
0078         (
0079             return composed::do_((First &&)first_,
0080                                  (Second &&)second_,
0081                                  std::is_void<invoke_result_t<First &&, Ts...>>{},
0082                                  (Ts &&) ts...)
0083         )
0084         // clang-format on
0085     };
0086
0087     struct compose_fn
0088     {
0089         template<typename Second, typename First>
0090         constexpr composed<Second, First> operator()(Second second, First first) const
0091         {
0092             return {std::move(second), std::move(first)};
0093         }
0094     };
0095
0096     /// \ingroup group-functional
0097     /// \sa `compose_fn`
0098     RANGES_INLINE_VARIABLE(compose_fn, compose)
0099     /// @}
0100 } // namespace ranges
0101
0102 #include <range/v3/detail/epilogue.hpp>
0103
0104 #endif