| //===----------------------------------------------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef _LIBCPP___ITERATOR_PRODUCT_ITERATOR_H |
| #define _LIBCPP___ITERATOR_PRODUCT_ITERATOR_H |
| |
| // Product iterators are iterators that contain two or more underlying iterators. |
| // |
| // For example, std::flat_map stores its data into two separate containers, and its iterator |
| // is a proxy over two separate underlying iterators. The concept of product iterators |
| // allows algorithms to operate over these underlying iterators separately, opening the |
| // door to various optimizations. |
| // |
| // If __product_iterator_traits can be instantiated, the following functions and associated types must be provided: |
| // - static constexpr size_t Traits::__size |
| // The number of underlying iterators inside the product iterator. |
| // |
| // - template <size_t _N> |
| // static decltype(auto) Traits::__get_iterator_element(It&& __it) |
| // Returns the _Nth iterator element of the given product iterator. |
| // |
| // - template <class... _Iters> |
| // static _Iterator __make_product_iterator(_Iters&&...); |
| // Creates a product iterator from the given underlying iterators. |
| |
| #include <__config> |
| #include <__cstddef/size_t.h> |
| #include <__type_traits/enable_if.h> |
| #include <__type_traits/integral_constant.h> |
| #include <__utility/declval.h> |
| |
| #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) |
| # pragma GCC system_header |
| #endif |
| |
| _LIBCPP_BEGIN_NAMESPACE_STD |
| |
| template <class _Iterator> |
| struct __product_iterator_traits; |
| /* exposition-only: |
| { |
| static constexpr size_t __size = ...; |
| |
| template <size_t _N, class _Iter> |
| static decltype(auto) __get_iterator_element(_Iter&&); |
| |
| template <class... _Iters> |
| static _Iterator __make_product_iterator(_Iters&&...); |
| }; |
| */ |
| |
| template <class _Tp, size_t = 0> |
| struct __is_product_iterator : false_type {}; |
| |
| template <class _Tp> |
| struct __is_product_iterator<_Tp, sizeof(__product_iterator_traits<_Tp>) * 0> : true_type {}; |
| |
| template <class _Tp, size_t _Size, class = void> |
| struct __is_product_iterator_of_size : false_type {}; |
| |
| template <class _Tp, size_t _Size> |
| struct __is_product_iterator_of_size<_Tp, _Size, __enable_if_t<__product_iterator_traits<_Tp>::__size == _Size> > |
| : true_type {}; |
| |
| template <class _Iterator, size_t _Nth> |
| using __product_iterator_element_t _LIBCPP_NODEBUG = |
| decltype(__product_iterator_traits<_Iterator>::template __get_iterator_element<_Nth>(std::declval<_Iterator>())); |
| |
| _LIBCPP_END_NAMESPACE_STD |
| |
| #endif // _LIBCPP___ITERATOR_PRODUCT_ITERATOR_H |