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//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
// UNSUPPORTED: c++03, c++11, c++14, c++17
// UNSUPPORTED: libcpp-has-no-incomplete-ranges
// std::views::reverse
#include <ranges>
#include <cassert>
#include <concepts>
#include <iterator>
#include <utility>
#include "types.h"
template <class View, class T>
concept CanBePiped = requires (View&& view, T&& t) {
{ std::forward<View>(view) | std::forward<T>(t) };
};
constexpr bool test() {
int buf[] = {1, 2, 3};
// views::reverse(x) is equivalent to x.base() if x is a reverse_view
{
{
BidirRange view(buf, buf + 3);
std::ranges::reverse_view<BidirRange> reversed(view);
std::same_as<BidirRange> auto result = std::views::reverse(reversed);
assert(result.begin_ == buf);
assert(result.end_ == buf + 3);
}
{
// Common use case is worth testing
BidirRange view(buf, buf + 3);
std::same_as<BidirRange> auto result = std::views::reverse(std::views::reverse(view));
assert(result.begin_ == buf);
assert(result.end_ == buf + 3);
}
}
// views::reverse(x) is equivalent to subrange{end, begin, size} if x is a
// sized subrange over reverse iterators
{
using It = bidirectional_iterator<int*>;
using Subrange = std::ranges::subrange<It, It, std::ranges::subrange_kind::sized>;
using ReverseIt = std::reverse_iterator<It>;
using ReverseSubrange = std::ranges::subrange<ReverseIt, ReverseIt, std::ranges::subrange_kind::sized>;
{
BidirRange view(buf, buf + 3);
ReverseSubrange subrange(ReverseIt(std::ranges::end(view)), ReverseIt(std::ranges::begin(view)), /* size */3);
std::same_as<Subrange> auto result = std::views::reverse(subrange);
assert(base(result.begin()) == buf);
assert(base(result.end()) == buf + 3);
}
{
// std::move into views::reverse
BidirRange view(buf, buf + 3);
ReverseSubrange subrange(ReverseIt(std::ranges::end(view)), ReverseIt(std::ranges::begin(view)), /* size */3);
std::same_as<Subrange> auto result = std::views::reverse(std::move(subrange));
assert(base(result.begin()) == buf);
assert(base(result.end()) == buf + 3);
}
{
// with a const subrange
BidirRange view(buf, buf + 3);
ReverseSubrange const subrange(ReverseIt(std::ranges::end(view)), ReverseIt(std::ranges::begin(view)), /* size */3);
std::same_as<Subrange> auto result = std::views::reverse(subrange);
assert(base(result.begin()) == buf);
assert(base(result.end()) == buf + 3);
}
}
// views::reverse(x) is equivalent to subrange{end, begin} if x is an
// unsized subrange over reverse iterators
{
using It = bidirectional_iterator<int*>;
using Subrange = std::ranges::subrange<It, It, std::ranges::subrange_kind::unsized>;
using ReverseIt = std::reverse_iterator<It>;
using ReverseSubrange = std::ranges::subrange<ReverseIt, ReverseIt, std::ranges::subrange_kind::unsized>;
{
BidirRange view(buf, buf + 3);
ReverseSubrange subrange(ReverseIt(std::ranges::end(view)), ReverseIt(std::ranges::begin(view)));
std::same_as<Subrange> auto result = std::views::reverse(subrange);
assert(base(result.begin()) == buf);
assert(base(result.end()) == buf + 3);
}
{
// std::move into views::reverse
BidirRange view(buf, buf + 3);
ReverseSubrange subrange(ReverseIt(std::ranges::end(view)), ReverseIt(std::ranges::begin(view)));
std::same_as<Subrange> auto result = std::views::reverse(std::move(subrange));
assert(base(result.begin()) == buf);
assert(base(result.end()) == buf + 3);
}
{
// with a const subrange
BidirRange view(buf, buf + 3);
ReverseSubrange const subrange(ReverseIt(std::ranges::end(view)), ReverseIt(std::ranges::begin(view)));
std::same_as<Subrange> auto result = std::views::reverse(subrange);
assert(base(result.begin()) == buf);
assert(base(result.end()) == buf + 3);
}
}
// Otherwise, views::reverse(x) is equivalent to ranges::reverse_view{x}
{
BidirRange view(buf, buf + 3);
std::same_as<std::ranges::reverse_view<BidirRange>> auto result = std::views::reverse(view);
assert(base(result.begin().base()) == buf + 3);
assert(base(result.end().base()) == buf);
}
// Test that std::views::reverse is a range adaptor
{
// Test `v | views::reverse`
{
BidirRange view(buf, buf + 3);
std::same_as<std::ranges::reverse_view<BidirRange>> auto result = view | std::views::reverse;
assert(base(result.begin().base()) == buf + 3);
assert(base(result.end().base()) == buf);
}
// Test `adaptor | views::reverse`
{
BidirRange view(buf, buf + 3);
auto f = [](int i) { return i; };
auto const partial = std::views::transform(f) | std::views::reverse;
using Result = std::ranges::reverse_view<std::ranges::transform_view<BidirRange, decltype(f)>>;
std::same_as<Result> auto result = partial(view);
assert(base(result.begin().base().base()) == buf + 3);
assert(base(result.end().base().base()) == buf);
}
// Test `views::reverse | adaptor`
{
BidirRange view(buf, buf + 3);
auto f = [](int i) { return i; };
auto const partial = std::views::reverse | std::views::transform(f);
using Result = std::ranges::transform_view<std::ranges::reverse_view<BidirRange>, decltype(f)>;
std::same_as<Result> auto result = partial(view);
assert(base(result.begin().base().base()) == buf + 3);
assert(base(result.end().base().base()) == buf);
}
// Check SFINAE friendliness
{
struct NotABidirRange { };
static_assert(!std::is_invocable_v<decltype(std::views::reverse)>);
static_assert(!std::is_invocable_v<decltype(std::views::reverse), NotABidirRange>);
static_assert( CanBePiped<BidirRange, decltype(std::views::reverse)>);
static_assert( CanBePiped<BidirRange&, decltype(std::views::reverse)>);
static_assert(!CanBePiped<NotABidirRange, decltype(std::views::reverse)>);
}
}
{
static_assert(std::same_as<decltype(std::views::reverse), decltype(std::ranges::views::reverse)>);
}
return true;
}
int main(int, char**) {
test();
static_assert(test());
return 0;
}
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