folly/folly/container/Array.h

/*
 * Copyright (c) Meta Platforms, Inc. and 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.
 */
/**
 * Helper functions to create std::arrays.
 *
 * @file container/Array.h
 * @refcode folly/docs/examples/folly/container/Array.cpp
 */

#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 {
is_ref_wrapper;

not_ref_wrapper;

template <typename D, typename...>
struct return_type_helper { … };
return_type_helper<void, TList...>;

return_type;
} // namespace array_detail

/// Constructs a std::array with the given argument list.
///
/// @param t  The values to be put in the array.
template <typename D = void, typename... TList>
constexpr array_detail::return_type<D, TList...> make_array(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...>) { … }
} // namespace array_detail

/// Generates a std::array<..., Size> with elements m(i) for i in [0, Size).
///
/// @tparam Size  The size of the array
/// @param make  The generator that makes the array elements. ret[i] = make(i)
template <std::size_t Size, typename MakeItem>
constexpr auto make_array_with(MakeItem const& make) { … }

} // namespace folly