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>
107 lines
3.5 KiB
C++
107 lines
3.5 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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#include <cassert>
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#include <concepts>
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#include <memory>
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#include <ranges>
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#include <type_traits>
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#include <utility>
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#include <vector>
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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 Iterator>
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struct Range {
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using Sentinel = sentinel_wrapper<Iterator>;
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constexpr Iterator begin() { return Iterator(data_.data()); }
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constexpr Sentinel end() { return Sentinel(Iterator(data_.data() + data_.size())); }
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private:
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std::vector<int> data_ = {0, 1, 2, 3};
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};
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template <class Range, class Allocator>
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constexpr bool test_range() {
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Range r;
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using elements_of_t = std::ranges::elements_of<Range&, Allocator>;
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{
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// constructor
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std::same_as<elements_of_t> decltype(auto) e = std::ranges::elements_of(r, Allocator());
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std::same_as<Range&> decltype(auto) range = e.range;
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assert(std::ranges::distance(range) == 4);
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[[maybe_unused]] std::same_as<Allocator> decltype(auto) allocator = e.allocator;
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}
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{
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// designated initializer
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std::same_as<elements_of_t> decltype(auto) e = std::ranges::elements_of{
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.range = r,
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.allocator = Allocator(),
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};
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std::same_as<Range&> decltype(auto) range = e.range;
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assert(&range == &r);
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assert(std::ranges::distance(range) == 4);
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[[maybe_unused]] std::same_as<Allocator> decltype(auto) allocator = e.allocator;
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}
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{
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// copy constructor
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std::same_as<elements_of_t> decltype(auto) e = std::ranges::elements_of(r, Allocator());
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std::same_as<elements_of_t> auto copy = e;
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std::same_as<Range&> decltype(auto) range = e.range;
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std::same_as<Range&> decltype(auto) copy_range = copy.range;
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assert(&range == &r);
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assert(&range == ©_range);
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assert(std::ranges::distance(range) == 4);
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[[maybe_unused]] std::same_as<Allocator> decltype(auto) copy_allocator = copy.allocator;
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}
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using elements_of_r_t = std::ranges::elements_of<Range&&, Allocator>;
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{
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// move constructor
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std::same_as<elements_of_r_t> decltype(auto) e = std::ranges::elements_of(std::move(r), Allocator());
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std::same_as<elements_of_r_t> auto copy = std::move(e);
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std::same_as<Range&&> decltype(auto) range = std::move(e.range);
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std::same_as<Range&&> decltype(auto) copy_range = std::move(copy.range);
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assert(&range == &r);
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assert(&range == ©_range);
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assert(std::ranges::distance(range) == 4);
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[[maybe_unused]] std::same_as<Allocator> decltype(auto) copy_allocator = copy.allocator;
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}
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return true;
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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_range<Range<Iterator>, Allocator>();
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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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