fa79e0a400
## Introduction This patch implements `ranges::elements_of` from [P2502R2](https://wg21.link/P2502R2). Specializations of `elements_of` encapsulate a range and act as a tag in overload sets to disambiguate when a range should be treated as a sequence rather than a single value. ```cpp template <bool YieldElements> std::generator<std::any> f(std::ranges::input_range auto &&r) { if constexpr (YieldElements) { co_yield std::ranges::elements_of(r); } else { co_yield r; } } ``` ## Reference - [P2502R2: `std::generator`: Synchronous Coroutine Generator for Ranges](https://wg21.link/P2502R2) - [[range.elementsof]](https://eel.is/c++draft/range.elementsof) Partially addresses #105226 --------- Co-authored-by: Louis Dionne <ldionne.2@gmail.com> Co-authored-by: A. Jiang <de34@live.cn>
101 lines
2.8 KiB
C++
101 lines
2.8 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
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// <ranges>
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//
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// template<range R, class Allocator = allocator<byte>>
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// struct std::ranges::elements_of;
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//
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// template<class R, class Allocator = allocator<byte>>
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// elements_of(R&&, Allocator = Allocator()) -> elements_of<R&&, Allocator>;
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#include <concepts>
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#include <cstddef>
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#include <memory>
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#include <ranges>
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#include <utility>
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#include "min_allocator.h"
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#include "test_allocator.h"
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#include "test_iterators.h"
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template <class Allocator, class Range>
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constexpr void test_impl() {
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Allocator a;
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// With a lvalue range
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{
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Range r;
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std::ranges::elements_of elements(r);
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static_assert(std::same_as<decltype(elements), std::ranges::elements_of<Range&, std::allocator<std::byte>>>);
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}
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// With a rvalue range
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{
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Range r;
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std::ranges::elements_of elements(std::move(r));
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static_assert(std::same_as<decltype(elements), std::ranges::elements_of<Range&&, std::allocator<std::byte>>>);
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}
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// With lvalue range and allocator
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{
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Range r;
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std::ranges::elements_of elements(r, a);
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static_assert(std::same_as<decltype(elements), std::ranges::elements_of<Range&, Allocator>>);
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}
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// With rvalue range and allocator
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{
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Range r;
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std::ranges::elements_of elements(std::move(r), Allocator());
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static_assert(std::same_as<decltype(elements), std::ranges::elements_of<Range&&, Allocator>>);
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}
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// Ensure we can use designated initializers
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{
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// lvalues
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{
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Range r;
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std::ranges::elements_of elements{.range = r, .allocator = a};
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static_assert(std::same_as<decltype(elements), std::ranges::elements_of<Range&, Allocator>>);
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}
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// rvalues
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{
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Range r;
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std::ranges::elements_of elements{.range = std::move(r), .allocator = Allocator()};
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static_assert(std::same_as<decltype(elements), std::ranges::elements_of<Range&&, Allocator>>);
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}
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}
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}
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template <class Iterator>
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struct Range {
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Iterator begin() const;
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sentinel_wrapper<Iterator> end() const;
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};
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constexpr bool test() {
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types::for_each(types::type_list<std::allocator<std::byte>, min_allocator<std::byte>, test_allocator<std::byte>>{},
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[]<class Allocator> {
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types::for_each(types::cpp20_input_iterator_list<int*>{}, []<class Iterator> {
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test_impl<Allocator, Range<Iterator>>();
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});
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});
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return true;
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}
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int main(int, char**) {
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test();
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static_assert(test());
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return 0;
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}
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