/* * Copyright (c) Facebook, Inc. and its affiliates. * * 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. */ #pragma once #include <array> #include <type_traits> #include <utility> #include <folly/CPortability.h> #include <folly/Traits.h> #include <folly/Utility.h> namespace folly { namespace array_detail { template <class T> using is_ref_wrapper = detail::is_instantiation_of<std::reference_wrapper, T>; template <typename T> using not_ref_wrapper = folly::Negation<is_ref_wrapper<typename std::decay<T>::type>>; template <typename D, typename...> struct return_type_helper { using type = D; }; template <typename... TList> struct return_type_helper<void, TList...> { static_assert( folly::Conjunction<not_ref_wrapper<TList>...>::value, "TList cannot contain reference_wrappers when D is void"); using type = typename std::common_type<TList...>::type; }; template <typename D, typename... TList> using return_type = std:: array<typename return_type_helper<D, TList...>::type, sizeof...(TList)>; } // namespace array_detail template <typename D = void, typename... TList> constexpr array_detail::return_type<D, TList...> make_array(TList&&... t) { using value_type = typename array_detail::return_type_helper<D, TList...>::type; return {{static_cast<value_type>(std::forward<TList>(t))...}}; } namespace array_detail { template <typename MakeItem, std::size_t... Index> FOLLY_ERASE constexpr auto make_array_with_( MakeItem const& make, std::index_sequence<Index...>) { return std::array<decltype(make(0)), sizeof...(Index)>{{make(Index)...}}; } } // namespace array_detail // make_array_with // // Constructs a std::array<..., Size> with elements m(i) for i in [0, Size). template <std::size_t Size, typename MakeItem> constexpr auto make_array_with(MakeItem const& make) { return array_detail::make_array_with_(make, std::make_index_sequence<Size>{}); } } // namespace folly