.. _program_listing_file_include_beluga_actions_assign.hpp:

Program Listing for File assign.hpp
===================================

|exhale_lsh| :ref:`Return to documentation for file <file_include_beluga_actions_assign.hpp>` (``include/beluga/actions/assign.hpp``)

.. |exhale_lsh| unicode:: U+021B0 .. UPWARDS ARROW WITH TIP LEFTWARDS

.. code-block:: cpp

   // Copyright 2024 Ekumen, Inc.
   //
   // Licensed under the Apache License, Version 2.0 (the "License");
   // you may not use this file except in compliance with the License.
   // You may obtain a copy of the License at
   //
   //     http://www.apache.org/licenses/LICENSE-2.0
   //
   // Unless required by applicable law or agreed to in writing, software
   // distributed under the License is distributed on an "AS IS" BASIS,
   // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   // See the License for the specific language governing permissions and
   // limitations under the License.
   
   #ifndef BELUGA_ACTIONS_ASSIGN_HPP
   #define BELUGA_ACTIONS_ASSIGN_HPP
   
   #include <range/v3/action/action.hpp>
   #include <range/v3/functional/bind_back.hpp>
   #include <range/v3/range/conversion.hpp>
   #include <range/v3/view/view.hpp>
   
   namespace beluga::actions {
   
   
   template <class T, class = void>
   struct is_range_closure : std::false_type {};
   
   template <class T>
   struct is_range_closure<ranges::actions::action_closure<T>> : std::true_type {};
   
   template <class T>
   struct is_range_closure<ranges::views::view_closure<T>> : std::true_type {};
   
   template <class T>
   inline constexpr bool is_range_closure_v = is_range_closure<T>::value;
   
   
   namespace detail {
   
   struct assign_fn {
     template <
         class Range,
         class Fn,
         std::enable_if_t<ranges::range<Range>, int> = 0,
         std::enable_if_t<is_range_closure_v<Fn>, int> = 0>
     constexpr auto operator()(Range& range, Fn fn) const -> Range& {
       auto&& view = fn(range);
       if constexpr (!std::is_same_v<Range, std::decay_t<decltype(view)>>) {
         // If the result of invoking the closure is not the range itself,
         // then we need to convert the view and assign it to the input range.
         range = std::move(view) | ranges::to<Range>;
       }
       return range;
     }
   
   
     template <class Fn, std::enable_if_t<is_range_closure_v<Fn>, int> = 0>
     friend constexpr auto operator|(Fn fn, assign_fn) {
       return ranges::make_action_closure(ranges::bind_back(assign_fn{}, std::move(fn)));
     }
   };
   
   }  // namespace detail
   
   
   inline constexpr detail::assign_fn assign;
   
   }  // namespace beluga::actions
   
   #endif