[libcxx] adds ranges::fold_left_with_iter and ranges::fold_left (#75259)

Notable things in this commit:

* refactors `__indirect_binary_left_foldable`, making it slightly
different (but equivalent) to _`indirect-binary-left-foldable`_, which
improves readability (a [patch to the Working Paper][patch] was made)
* omits `__cpo` namespace, since it is not required for implementing
niebloids (a cleanup should happen in 2024)
* puts tests ensuring invocable robustness and dangling correctness
inside the correctness testing to ensure that the algorithms' results
are still correct

[patch]: https://github.com/cplusplus/draft/pull/6734
This commit is contained in:
Christopher Di Bella 2023-12-19 21:57:50 -08:00 committed by GitHub
parent 037c220702
commit 3903438860
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
18 changed files with 1062 additions and 32 deletions

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@ -10,3 +10,9 @@ C++23,`shift_right <https://wg21.link/p2440r1>`_,Unassigned,No patch yet,Not sta
C++23,`iota (algorithm) <https://wg21.link/p2440r1>`_,Unassigned,No patch yet,Not started
C++23,`fold <https://wg21.link/p2322r5>`_,Unassigned,No patch yet,Not started
C++23,`contains <https://wg21.link/p2302r2>`_,Zijun Zhao,No patch yet,In Progress
C++23,`fold_left_with_iter <https://wg21.link/p2322r6>`_,Christopher Di Bella,N/A,Complete
C++23,`fold_left <https://wg21.link/p2322r6>`_,Christopher Di Bella,N/A,Complete
C++23,`fold_left_first_with_iter <https://wg21.link/p2322r6>`_,Christopher Di Bella,N/A,In progress
C++23,`fold_left_first <https://wg21.link/p2322r6>`_,Christopher Di Bella,N/A,In progress
C++23,`fold_right <https://wg21.link/p2322r6>`_,Christopher Di Bella,N/A,In progress
C++23,`fold_right_last <https://wg21.link/p2322r6>`_,Christopher Di Bella,N/A,In progress

1 Standard Algorithm Assignee CL Status
10 C++23 `iota (algorithm) <https://wg21.link/p2440r1>`_ Unassigned No patch yet Not started
11 C++23 `fold <https://wg21.link/p2322r5>`_ Unassigned No patch yet Not started
12 C++23 `contains <https://wg21.link/p2302r2>`_ Zijun Zhao No patch yet In Progress
13 C++23 `fold_left_with_iter <https://wg21.link/p2322r6>`_ Christopher Di Bella N/A Complete
14 C++23 `fold_left <https://wg21.link/p2322r6>`_ Christopher Di Bella N/A Complete
15 C++23 `fold_left_first_with_iter <https://wg21.link/p2322r6>`_ Christopher Di Bella N/A In progress
16 C++23 `fold_left_first <https://wg21.link/p2322r6>`_ Christopher Di Bella N/A In progress
17 C++23 `fold_right <https://wg21.link/p2322r6>`_ Christopher Di Bella N/A In progress
18 C++23 `fold_right_last <https://wg21.link/p2322r6>`_ Christopher Di Bella N/A In progress

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@ -23,6 +23,7 @@ set(files
__algorithm/find_if.h
__algorithm/find_if_not.h
__algorithm/find_segment_if.h
__algorithm/fold.h
__algorithm/for_each.h
__algorithm/for_each_n.h
__algorithm/for_each_segment.h

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@ -0,0 +1,125 @@
// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// 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___ALGORITHM_FOLD_H
#define _LIBCPP___ALGORITHM_FOLD_H
#include <__concepts/assignable.h>
#include <__concepts/convertible_to.h>
#include <__concepts/invocable.h>
#include <__concepts/movable.h>
#include <__config>
#include <__functional/invoke.h>
#include <__functional/reference_wrapper.h>
#include <__iterator/concepts.h>
#include <__iterator/iterator_traits.h>
#include <__iterator/next.h>
#include <__ranges/access.h>
#include <__ranges/concepts.h>
#include <__ranges/dangling.h>
#include <__type_traits/decay.h>
#include <__type_traits/invoke.h>
#include <__utility/forward.h>
#include <__utility/move.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
#if _LIBCPP_STD_VER >= 23
namespace ranges {
template <class _Ip, class _Tp>
struct in_value_result {
_LIBCPP_NO_UNIQUE_ADDRESS _Ip in;
_LIBCPP_NO_UNIQUE_ADDRESS _Tp value;
template <class _I2, class _T2>
requires convertible_to<const _Ip&, _I2> && convertible_to<const _Tp&, _T2>
_LIBCPP_HIDE_FROM_ABI constexpr operator in_value_result<_I2, _T2>() const& {
return {in, value};
}
template <class _I2, class _T2>
requires convertible_to<_Ip, _I2> && convertible_to<_Tp, _T2>
_LIBCPP_HIDE_FROM_ABI constexpr operator in_value_result<_I2, _T2>() && {
return {std::move(in), std::move(value)};
}
};
template <class _Ip, class _Tp>
using fold_left_with_iter_result = in_value_result<_Ip, _Tp>;
template <class _Fp, class _Tp, class _Ip, class _Rp, class _Up = decay_t<_Rp>>
concept __indirectly_binary_left_foldable_impl =
convertible_to<_Rp, _Up> && //
movable<_Tp> && //
movable<_Up> && //
convertible_to<_Tp, _Up> && //
invocable<_Fp&, _Up, iter_reference_t<_Ip>> && //
assignable_from<_Up&, invoke_result_t<_Fp&, _Up, iter_reference_t<_Ip>>>;
template <class _Fp, class _Tp, class _Ip>
concept __indirectly_binary_left_foldable =
copy_constructible<_Fp> && //
invocable<_Fp&, _Tp, iter_reference_t<_Ip>> && //
__indirectly_binary_left_foldable_impl<_Fp, _Tp, _Ip, invoke_result_t<_Fp&, _Tp, iter_reference_t<_Ip>>>;
struct __fold_left_with_iter {
template <input_iterator _Ip, sentinel_for<_Ip> _Sp, class _Tp, __indirectly_binary_left_foldable<_Tp, _Ip> _Fp>
_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI static constexpr auto
operator()(_Ip __first, _Sp __last, _Tp __init, _Fp __f) {
using _Up = decay_t<invoke_result_t<_Fp&, _Tp, iter_reference_t<_Ip>>>;
if (__first == __last) {
return fold_left_with_iter_result<_Ip, _Up>{std::move(__first), _Up(std::move(__init))};
}
_Up __result = std::invoke(__f, std::move(__init), *__first);
for (++__first; __first != __last; ++__first) {
__result = std::invoke(__f, std::move(__result), *__first);
}
return fold_left_with_iter_result<_Ip, _Up>{std::move(__first), std::move(__result)};
}
template <input_range _Rp, class _Tp, __indirectly_binary_left_foldable<_Tp, iterator_t<_Rp>> _Fp>
_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI static constexpr auto operator()(_Rp&& __r, _Tp __init, _Fp __f) {
auto __result = operator()(ranges::begin(__r), ranges::end(__r), std::move(__init), std::ref(__f));
using _Up = decay_t<invoke_result_t<_Fp&, _Tp, range_reference_t<_Rp>>>;
return fold_left_with_iter_result<borrowed_iterator_t<_Rp>, _Up>{std::move(__result.in), std::move(__result.value)};
}
};
inline constexpr auto fold_left_with_iter = __fold_left_with_iter();
struct __fold_left {
template <input_iterator _Ip, sentinel_for<_Ip> _Sp, class _Tp, __indirectly_binary_left_foldable<_Tp, _Ip> _Fp>
_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI static constexpr auto
operator()(_Ip __first, _Sp __last, _Tp __init, _Fp __f) {
return fold_left_with_iter(std::move(__first), std::move(__last), std::move(__init), std::ref(__f)).value;
}
template <input_range _Rp, class _Tp, __indirectly_binary_left_foldable<_Tp, iterator_t<_Rp>> _Fp>
_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI static constexpr auto operator()(_Rp&& __r, _Tp __init, _Fp __f) {
return fold_left_with_iter(ranges::begin(__r), ranges::end(__r), std::move(__init), std::ref(__f)).value;
}
};
inline constexpr auto fold_left = __fold_left();
} // namespace ranges
#endif // _LIBCPP_STD_VER >= 23
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___ALGORITHM_FOLD_H

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@ -42,6 +42,9 @@ namespace ranges {
template <class I>
struct in_found_result; // since C++20
template <class I, class T>
struct in_value_result; // since C++23
template<forward_iterator I, sentinel_for<I> S, class Proj = identity,
indirect_strict_weak_order<projected<I, Proj>> Comp = ranges::less> // since C++20
constexpr I min_element(I first, S last, Comp comp = {}, Proj proj = {});
@ -881,6 +884,23 @@ namespace ranges {
ranges::search_n(R&& r, range_difference_t<R> count,
const T& value, Pred pred = {}, Proj proj = {}); // since C++20
template<input_iterator I, sentinel_for<I> S, class T,
indirectly-binary-left-foldable<T, I> F>
constexpr auto ranges::fold_left(I first, S last, T init, F f); // since C++23
template<input_range R, class T, indirectly-binary-left-foldable<T, iterator_t<R>> F>
constexpr auto fold_left(R&& r, T init, F f); // since C++23
template<class I, class T>
using fold_left_with_iter_result = in_value_result<I, T>; // since C++23
template<input_iterator I, sentinel_for<I> S, class T,
indirectly-binary-left-foldable<T, I> F>
constexpr see below fold_left_with_iter(I first, S last, T init, F f); // since C++23
template<input_range R, class T, indirectly-binary-left-foldable<T, iterator_t<R>> F>
constexpr see below fold_left_with_iter(R&& r, T init, F f); // since C++23
template<forward_iterator I1, sentinel_for<I1> S1, forward_iterator I2, sentinel_for<I2> S2,
class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity>
requires indirectly_comparable<I1, I2, Pred, Proj1, Proj2>
@ -1786,6 +1806,7 @@ template <class BidirectionalIterator, class Compare>
#include <__algorithm/find_first_of.h>
#include <__algorithm/find_if.h>
#include <__algorithm/find_if_not.h>
#include <__algorithm/fold.h>
#include <__algorithm/for_each.h>
#include <__algorithm/for_each_n.h>
#include <__algorithm/generate.h>

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@ -666,6 +666,7 @@ module std_private_algorithm_find_first_of [system
module std_private_algorithm_find_if [system] { header "__algorithm/find_if.h" }
module std_private_algorithm_find_if_not [system] { header "__algorithm/find_if_not.h" }
module std_private_algorithm_find_segment_if [system] { header "__algorithm/find_segment_if.h" }
module std_private_algorithm_fold [system] { header "__algorithm/fold.h" }
module std_private_algorithm_for_each [system] { header "__algorithm/for_each.h" }
module std_private_algorithm_for_each_n [system] { header "__algorithm/for_each_n.h" }
module std_private_algorithm_for_each_segment [system] { header "__algorithm/for_each_segment.h" }

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@ -16,7 +16,7 @@ export namespace std {
using std::ranges::in_in_result;
using std::ranges::in_out_out_result;
using std::ranges::in_out_result;
// using std::ranges::in_value_result;
using std::ranges::in_value_result;
using std::ranges::min_max_result;
// using std::ranges::out_value_result;
} // namespace ranges
@ -157,15 +157,15 @@ export namespace std {
// [alg.ends.with], ends with
using std::ranges::ends_with;
# if 0
// [alg.fold], fold
using std::ranges::fold_left;
using std::ranges::fold_left_with_iter;
using std::ranges::fold_left_with_iter_result;
# if 0
using std::ranges::fold_left_first;
using std::ranges::fold_right;
using std::ranges::fold_right_last;
using std::ranges::fold_left_with_iter;
using std::ranges::fold_left_with_iter_result;
using std::ranges::fold_left_with_iter;
using std::ranges::fold_left_first_with_iter;
using std::ranges::fold_left_first_with_iter;
# endif

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@ -12,6 +12,8 @@
#include <algorithm>
#include "test_macros.h"
void test() {
int range[1];
int* iter = range;
@ -87,4 +89,15 @@ void test() {
std::ranges::unique(iter, iter); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::ranges::upper_bound(range, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
std::ranges::upper_bound(iter, iter, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
#if TEST_STD_VER >= 23
std::ranges::fold_left(range, 0, std::plus());
// expected-warning@-1{{ignoring return value of function declared with 'nodiscard' attribute}}
std::ranges::fold_left(iter, iter, 0, std::plus());
// expected-warning@-1{{ignoring return value of function declared with 'nodiscard' attribute}}
std::ranges::fold_left_with_iter(range, 0, std::plus());
// expected-warning@-1{{ignoring return value of function declared with 'nodiscard' attribute}}
std::ranges::fold_left_with_iter(iter, iter, 0, std::plus());
// expected-warning@-1{{ignoring return value of function declared with 'nodiscard' attribute}}
#endif
}

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@ -0,0 +1,320 @@
//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
// <algorithm>
// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
// template<input_iterator I, sentinel_for<I> S, class T,
// indirectly-binary-left-foldable<T, I> F>
// constexpr see below ranges::fold_left_with_iter(I first, S last, T init, F f);
//
// template<input_range R, class T, indirectly-binary-left-foldable<T, iterator_t<R>> F>
// constexpr see below ranges::fold_left_with_iter(R&& r, T init, F f);
// template<input_iterator I, sentinel_for<I> S, class T,
// indirectly-binary-left-foldable<T, I> F>
// constexpr see below ranges::fold_left(I first, S last, T init, F f);
//
// template<input_range R, class T, indirectly-binary-left-foldable<T, iterator_t<R>> F>
// constexpr see below ranges::fold_left(R&& r, T init, F f);
#include <algorithm>
#include <cassert>
#include <concepts>
#include <deque>
#include <forward_list>
#include <functional>
#include <iterator>
#include <list>
#include <ranges>
#include <string_view>
#include <string>
#include <vector>
#include "test_macros.h"
#include "test_range.h"
#include "invocable_with_telemetry.h"
#include "maths.h"
#if !defined(TEST_HAS_NO_LOCALIZATION)
# include <sstream>
#endif
using std::ranges::fold_left;
using std::ranges::fold_left_with_iter;
template <class Result, class Range, class T>
concept is_in_value_result =
std::same_as<Result, std::ranges::fold_left_with_iter_result<std::ranges::iterator_t<Range>, T>>;
template <class Result, class T>
concept is_dangling_with = std::same_as<Result, std::ranges::fold_left_with_iter_result<std::ranges::dangling, T>>;
struct Long {
int value;
constexpr Long(int const x) : value(x) {}
constexpr Long plus(int const x) const { return Long{value + x}; }
friend constexpr bool operator==(Long const& x, Long const& y) = default;
};
template <std::ranges::input_range R, class T, class F, std::equality_comparable Expected>
requires std::copyable<R>
constexpr void check_iterator(R& r, T const& init, F f, Expected const& expected) {
{
is_in_value_result<R, Expected> decltype(auto) result = fold_left_with_iter(r.begin(), r.end(), init, f);
assert(result.in == r.end());
assert(result.value == expected);
}
{
auto telemetry = invocable_telemetry();
auto f2 = invocable_with_telemetry(f, telemetry);
is_in_value_result<R, Expected> decltype(auto) result = fold_left_with_iter(r.begin(), r.end(), init, f2);
assert(result.in == r.end());
assert(result.value == expected);
assert(telemetry.invocations == std::ranges::distance(r));
assert(telemetry.moves == 0);
assert(telemetry.copies == 1);
}
{
std::same_as<Expected> decltype(auto) result = fold_left(r.begin(), r.end(), init, f);
assert(result == expected);
}
{
auto telemetry = invocable_telemetry();
auto f2 = invocable_with_telemetry(f, telemetry);
std::same_as<Expected> decltype(auto) result = fold_left(r.begin(), r.end(), init, f2);
assert(result == expected);
assert(telemetry.invocations == std::ranges::distance(r));
assert(telemetry.moves == 0);
assert(telemetry.copies == 1);
}
}
template <std::ranges::input_range R, class T, class F, std::equality_comparable Expected>
requires std::copyable<R>
constexpr void check_lvalue_range(R& r, T const& init, F f, Expected const& expected) {
{
is_in_value_result<R, Expected> decltype(auto) result = fold_left_with_iter(r, init, f);
assert(result.in == r.end());
assert(result.value == expected);
}
{
auto telemetry = invocable_telemetry();
auto f2 = invocable_with_telemetry(f, telemetry);
std::same_as<Expected> decltype(auto) result = fold_left(r, init, f2);
assert(result == expected);
assert(telemetry.invocations == std::ranges::distance(r));
assert(telemetry.moves == 0);
assert(telemetry.copies == 1);
}
{
std::same_as<Expected> decltype(auto) result = fold_left(r, init, f);
assert(result == expected);
}
{
auto telemetry = invocable_telemetry();
auto f2 = invocable_with_telemetry(f, telemetry);
std::same_as<Expected> decltype(auto) result = fold_left(r, init, f2);
assert(result == expected);
assert(telemetry.invocations == std::ranges::distance(r));
assert(telemetry.moves == 0);
assert(telemetry.copies == 1);
}
}
template <std::ranges::input_range R, class T, class F, std::equality_comparable Expected>
requires std::copyable<R>
constexpr void check_rvalue_range(R& r, T const& init, F f, Expected const& expected) {
{
auto r2 = r;
is_dangling_with<Expected> decltype(auto) result = fold_left_with_iter(std::move(r2), init, f);
assert(result.value == expected);
}
{
auto telemetry = invocable_telemetry();
auto f2 = invocable_with_telemetry(f, telemetry);
auto r2 = r;
is_dangling_with<Expected> decltype(auto) result = fold_left_with_iter(std::move(r2), init, f2);
assert(result.value == expected);
assert(telemetry.invocations == std::ranges::distance(r));
assert(telemetry.moves == 0);
assert(telemetry.copies == 1);
}
{
auto r2 = r;
std::same_as<Expected> decltype(auto) result = fold_left(std::move(r2), init, f);
assert(result == expected);
}
{
auto telemetry = invocable_telemetry();
auto f2 = invocable_with_telemetry(f, telemetry);
auto r2 = r;
std::same_as<Expected> decltype(auto) result = fold_left(std::move(r2), init, f2);
assert(result == expected);
assert(telemetry.invocations == std::ranges::distance(r));
assert(telemetry.moves == 0);
assert(telemetry.copies == 1);
}
}
template <std::ranges::input_range R, class T, class F, std::equality_comparable Expected>
requires std::copyable<R>
constexpr void check(R r, T const& init, F f, Expected const& expected) {
check_iterator(r, init, f, expected);
check_lvalue_range(r, init, f, expected);
check_rvalue_range(r, init, f, expected);
}
constexpr void empty_range_test_case() {
auto const data = std::vector<int>{};
check(data, 100, std::plus(), 100);
check(data, -100, std::multiplies(), -100);
check(data | std::views::take_while([](auto) { return false; }), 1.23, std::plus(), 1.23);
check(data, Long(52), &Long::plus, Long(52));
}
constexpr void common_range_test_case() {
auto const data = std::vector<int>{1, 2, 3, 4};
check(data, 0, std::plus(), triangular_sum(data));
check(data, 1, std::multiplies(), factorial(data.back()));
auto multiply_with_prev = [n = 1](auto const x, auto const y) mutable {
auto const result = x * y * n;
n = y;
return static_cast<std::size_t>(result);
};
check(data, 1, multiply_with_prev, factorial(data.size()) * factorial(data.size() - 1));
auto fib = [n = 1](auto x, auto) mutable {
auto old_x = x;
x += n;
n = old_x;
return x;
};
check(data, 0, fib, fibonacci(data.back()));
check(data, Long(0), &Long::plus, Long(triangular_sum(data)));
}
constexpr void non_common_range_test_case() {
auto parse = [](std::string_view const s) {
return s == "zero" ? 0.0
: s == "one" ? 1.0
: s == "two" ? 2.0
: s == "three" ? 3.0
: s == "four" ? 4.0
: s == "five" ? 5.0
: s == "six" ? 6.0
: s == "seven" ? 7.0
: s == "eight" ? 8.0
: s == "nine" ? 9.0
: (assert(false), 10.0); // the number here is arbitrary
};
{
auto data = std::vector<std::string>{"five", "three", "two", "six", "one", "four"};
auto range = data | std::views::transform(parse);
check(range, 0, std::plus(), triangular_sum(range));
}
{
auto data = std::string("five three two six one four");
auto to_string_view = [](auto&& r) {
auto const n = std::ranges::distance(r);
return std::string_view(&*r.begin(), n);
};
auto range =
std::views::lazy_split(data, ' ') | std::views::transform(to_string_view) | std::views::transform(parse);
check(range, 0, std::plus(), triangular_sum(range));
}
}
constexpr bool test_case() {
empty_range_test_case();
common_range_test_case();
non_common_range_test_case();
return true;
}
// Most containers aren't constexpr
void runtime_only_test_case() {
#if !defined(TEST_HAS_NO_LOCALIZATION)
{ // istream_view is a genuine input range and needs specific handling.
constexpr auto raw_data = "Shells Orange Syrup Baratie Cocoyashi Loguetown";
constexpr auto expected = "WindmillShellsOrangeSyrupBaratieCocoyashiLoguetown";
auto const init = std::string("Windmill");
{
auto input = std::istringstream(raw_data);
auto data = std::views::istream<std::string>(input);
is_in_value_result<std::ranges::basic_istream_view<std::string, char>, std::string> decltype(auto) result =
fold_left_with_iter(data.begin(), data.end(), init, std::plus());
assert(result.in == data.end());
assert(result.value == expected);
}
{
auto input = std::istringstream(raw_data);
auto data = std::views::istream<std::string>(input);
is_in_value_result<std::ranges::basic_istream_view<std::string, char>, std::string> decltype(auto) result =
fold_left_with_iter(data, init, std::plus());
assert(result.in == data.end());
assert(result.value == expected);
}
{
auto input = std::istringstream(raw_data);
auto data = std::views::istream<std::string>(input);
assert(fold_left(data.begin(), data.end(), init, std::plus()) == expected);
}
{
auto input = std::istringstream(raw_data);
auto data = std::views::istream<std::string>(input);
assert(fold_left(data, init, std::plus()) == expected);
}
}
#endif
{
auto const data = std::forward_list<int>{1, 3, 5, 7, 9};
auto const n = std::ranges::distance(data);
auto const expected = static_cast<float>(n * n); // sum of n consecutive odd numbers = n^2
check(data, 0.0f, std::plus(), expected);
}
{
auto const data = std::list<int>{2, 4, 6, 8, 10, 12};
auto const expected = triangular_sum(data);
check(data, 0, std::plus<long>(), static_cast<long>(expected));
}
{
auto const data = std::deque<double>{-1.1, -2.2, -3.3, -4.4, -5.5, -6.6};
auto plus = [](int const x, double const y) { return x + y; };
auto const expected = -21.6; // int( 0.0) + -1.1 = 0 + -1.1 = -1.1
// int(- 1.1) + -2.2 = - 1 + -2.2 = -3.2
// int(- 3.2) + -3.3 = - 3 + -3.3 = -6.3
// int(- 6.3) + -4.4 = - 6 + -4.4 = -10.4
// int(-10.4) + -5.5 = -10 + -5.5 = -15.5
// int(-15.5) + -6.6 = -15 + -6.6 = -21.6.
check(data, 0.0, plus, expected);
}
}
int main(int, char**) {
test_case();
static_assert(test_case());
runtime_only_test_case();
return 0;
}

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@ -0,0 +1,259 @@
//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
// <algorithm>
// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
// Checks that `std::ranges::fold_left_with_iter`'s requirements reject parameters that don't meet
// the overloads' constraints.
#include <algorithm>
#include <concepts>
#include <cstddef>
#include <functional>
#include <iterator>
#include <ranges>
#include "test_iterators.h"
// FIXME(cjdb): deduplicate
struct bad_iterator_category {
using value_type = int;
using difference_type = std::ptrdiff_t;
using iterator_category = void;
value_type operator*() const;
bad_iterator_category& operator++();
void operator++(int);
};
// Covers indirectly_readable<I> too
template <std::input_or_output_iterator T>
requires(!std::input_iterator<T>)
void requires_input_iterator() {
struct bad_range {
T begin();
std::unreachable_sentinel_t end();
};
static_assert(!requires(bad_range r) {
std::ranges::fold_left_with_iter(r.begin(), r.end(), std::unreachable_sentinel, 0, std::plus());
});
static_assert(!requires(bad_range r) { std::ranges::fold_left_with_iter(r, 0, std::plus()); });
static_assert(!requires(bad_range r) {
std::ranges::fold_left(r.begin(), r.end(), std::unreachable_sentinel, 0, std::plus());
});
static_assert(!requires(bad_range r) { std::ranges::fold_left(r, 0, std::plus()); });
}
template <std::equality_comparable S>
requires(!std::sentinel_for<int*, S>)
void requires_sentinel() {
static_assert(!requires(S first, S last) { std::ranges::fold_left_with_iter(first, last, 0, std::plus()); });
static_assert(!requires(S first, S last) { std::ranges::fold_left(first, last, 0, std::plus()); });
}
struct non_copy_constructible_callable {
non_copy_constructible_callable(non_copy_constructible_callable&&) = default;
non_copy_constructible_callable(non_copy_constructible_callable const&) = delete;
int operator()(int, int) const;
};
template <class F>
requires(!std::copy_constructible<F>)
void requires_copy_constructible_F() {
static_assert(!requires(std::ranges::subrange<int*, int*> r, F f) {
std::ranges::fold_left_with_iter(r.begin(), r.end(), 0, std::move(f));
});
static_assert(!requires(std::ranges::subrange<int*, int*> r, F f) {
std::ranges::fold_left_with_iter(r, 0, std::move(f));
});
static_assert(!requires(std::ranges::subrange<int*, int*> r, F f) {
std::ranges::fold_left(r.begin(), r.end(), 0, std::move(f));
});
static_assert(!requires(std::ranges::subrange<int*, int*> r, F f) { std::ranges::fold_left(r, 0, std::move(f)); });
}
struct not_invocable_with_lvalue_rhs {
int operator()(int, int&&);
};
template <class F>
requires(!std::invocable<F&, int, std::iter_reference_t<int*>>)
void requires_raw_invocable() {
static_assert(!requires(std::ranges::subrange<int*, int*> r, F f) {
std::ranges::fold_left_with_iter(r.begin(), r.end(), 0, f);
});
static_assert(!requires(std::ranges::subrange<int*, int*> r, F f) { std::ranges::fold_left_with_iter(r, 0, f); });
static_assert(!requires(std::ranges::subrange<int*, int*> r, F f) {
std::ranges::fold_left(r.begin(), r.end(), 0, f);
});
static_assert(!requires(std::ranges::subrange<int*, int*> r, F f) { std::ranges::fold_left(r, 0, f); });
}
struct S {};
struct non_decayable_result {
S volatile& operator()(S, S) const;
};
template <std::invocable<S, std::iter_reference_t<S*>> F>
requires(!std::convertible_to<std::invoke_result_t<F&, S, std::iter_reference_t<S*>>,
std::decay_t<std::invoke_result_t<F&, S, std::iter_reference_t<S*>>>>)
void requires_decaying_invoke_result() {
static_assert(!requires(std::ranges::subrange<S*, S*> r, S init, F f) {
std::ranges::fold_left_with_iter(r.begin(), r.end(), init, f);
});
static_assert(!requires(std::ranges::subrange<S*, S*> r, S init, F f) {
std::ranges::fold_left_with_iter(r, init, f);
});
static_assert(!requires(std::ranges::subrange<S*, S*> r, S init, F f) {
std::ranges::fold_left(r.begin(), r.end(), init, f);
});
static_assert(!requires(std::ranges::subrange<S*, S*> r, S init, F f) { std::ranges::fold_left(r, init, f); });
}
struct non_movable {
non_movable(int);
non_movable(non_movable&&) = delete;
int apply(non_movable const&) const;
};
template <class T>
requires(!std::movable<T>)
void requires_movable_init() {
static_assert(!requires(std::ranges::subrange<T*, T*> r, T init) {
std::ranges::fold_left_with_iter(r.begin(), r.end(), init, &T::apply);
});
static_assert(!requires(std::ranges::subrange<T*, T*> r, T init) {
std::ranges::fold_left_with_iter(r, init, &T::apply);
});
static_assert(!requires(std::ranges::subrange<T*, T*> r, T init) {
std::ranges::fold_left(r.begin(), r.end(), init, &T::apply);
});
static_assert(!requires(std::ranges::subrange<T*, T*> r, T init) { std::ranges::fold_left(r, init, &T::apply); });
}
struct result_not_movable_after_decay {
result_not_movable_after_decay(int);
result_not_movable_after_decay(result_not_movable_after_decay&&) = delete;
result_not_movable_after_decay(result_not_movable_after_decay const&);
friend result_not_movable_after_decay const& operator+(int, result_not_movable_after_decay const&);
friend result_not_movable_after_decay const& operator+(result_not_movable_after_decay const&, int);
friend result_not_movable_after_decay const&
operator+(result_not_movable_after_decay const&, result_not_movable_after_decay const&);
};
template <class T>
requires(!std::movable<T>)
void requires_movable_decayed() {
static_assert(!requires(std::ranges::subrange<T*, T*> r) {
std::ranges::fold_left_with_iter(r.begin(), r.end(), 0, std::plus());
});
static_assert(!requires(std::ranges::subrange<T*, T*> r) { std::ranges::fold_left_with_iter(r, 0, std::plus()); });
static_assert(!requires(std::ranges::subrange<T*, T*> r) {
std::ranges::fold_left(r.begin(), r.end(), 0, T::apply);
});
static_assert(!requires(std::ranges::subrange<T*, T*> r) { std::ranges::fold_left(r, 0, std::plus()); });
}
struct not_convertible_to_int {
friend int operator+(not_convertible_to_int, not_convertible_to_int);
friend int operator+(not_convertible_to_int, int);
friend int operator+(int, not_convertible_to_int);
};
template <class T>
requires(!std::convertible_to<T, int>)
void requires_init_is_convertible_to_decayed() {
static_assert(!requires(std::ranges::subrange<int*, int*> r, T init) {
std::ranges::fold_left_with_iter(r.begin(), r.end(), init, std::plus());
});
static_assert(!requires(std::ranges::subrange<int*, int*> r, T init) {
std::ranges::fold_left_with_iter(r, init, std::plus());
});
static_assert(!requires(std::ranges::subrange<int*, int*> r, T init) {
std::ranges::fold_left(r.begin(), r.end(), init, std::plus());
});
static_assert(!requires(std::ranges::subrange<int*, int*> r, T init) {
std::ranges::fold_left(r, init, std::plus());
});
}
struct not_invocable_with_decayed {
not_invocable_with_decayed(int);
friend not_invocable_with_decayed& operator+(int, not_invocable_with_decayed&);
friend not_invocable_with_decayed& operator+(not_invocable_with_decayed&, int);
friend not_invocable_with_decayed& operator+(not_invocable_with_decayed volatile&, not_invocable_with_decayed&);
};
template <class T>
requires(!std::invocable<std::plus<>&, T, T&>)
void requires_invocable_with_decayed() {
static_assert(!requires(std::ranges::subrange<T*, T*> r, int init) {
std::ranges::fold_left_with_iter(r.begin(), r.end(), init, std::plus());
});
static_assert(!requires(std::ranges::subrange<T*, T*> r, int init) {
std::ranges::fold_left_with_iter(r, init, std::plus());
});
static_assert(!requires(std::ranges::subrange<T*, T*> r, int init) {
std::ranges::fold_left(r.begin(), r.end(), init, std::plus());
});
static_assert(!requires(std::ranges::subrange<T*, T*> r, int init) { std::ranges::fold_left(r, init, std::plus()); });
}
struct not_assignable_to_decayed {
not_assignable_to_decayed();
not_assignable_to_decayed(not_assignable_to_decayed&);
not_assignable_to_decayed(not_assignable_to_decayed const&);
not_assignable_to_decayed(not_assignable_to_decayed volatile&);
not_assignable_to_decayed(not_assignable_to_decayed const volatile&);
friend not_assignable_to_decayed volatile& operator+(not_assignable_to_decayed, not_assignable_to_decayed);
};
template <class T>
requires(!std::assignable_from<T&, T volatile&>)
void requires_assignable_from_invoke_result() {
static_assert(!requires(std::ranges::subrange<T*, T*> r, T init) {
std::ranges::fold_left_with_iter(r.begin(), r.end(), init, std::plus());
});
static_assert(!requires(std::ranges::subrange<T*, T*> r, T init) {
std::ranges::fold_left_with_iter(r, init, std::plus());
});
static_assert(!requires(std::ranges::subrange<T*, T*> r, T init) {
std::ranges::fold_left(r.begin(), r.end(), init, std::plus());
});
static_assert(!requires(std::ranges::subrange<T*, T*> r, T init) { std::ranges::fold_left(r, init, std::plus()); });
}
void test() {
requires_input_iterator<bad_iterator_category>();
requires_sentinel<cpp17_input_iterator<int*>>();
requires_copy_constructible_F<non_copy_constructible_callable>();
requires_raw_invocable<not_invocable_with_lvalue_rhs>();
requires_decaying_invoke_result<non_decayable_result>();
requires_movable_init<non_movable>();
requires_movable_decayed<result_not_movable_after_decay>();
requires_init_is_convertible_to_decayed<not_convertible_to_int>();
requires_invocable_with_decayed<not_invocable_with_decayed>();
requires_assignable_from_invoke_result<not_assignable_to_decayed>();
}

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@ -0,0 +1,104 @@
//===----------------------------------------------------------------------===//
//
// 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, c++20
// template <class I, class T>
// struct in_value_result;
#include <algorithm>
#include <cassert>
#include <type_traits>
#include <utility>
#include "MoveOnly.h"
struct A {
explicit A(int);
};
// no implicit conversion
static_assert(!std::is_constructible_v<std::ranges::in_value_result<A, A>, std::ranges::in_value_result<int, int>>);
struct B {
B(int);
};
// implicit conversion
static_assert(std::is_constructible_v<std::ranges::in_value_result<B, B>, std::ranges::in_value_result<int, int>>);
static_assert(std::is_constructible_v<std::ranges::in_value_result<B, B>, std::ranges::in_value_result<int, int>&>);
static_assert(
std::is_constructible_v<std::ranges::in_value_result<B, B>, const std::ranges::in_value_result<int, int>>);
static_assert(
std::is_constructible_v<std::ranges::in_value_result<B, B>, const std::ranges::in_value_result<int, int>&>);
struct C {
C(int&);
};
static_assert(!std::is_constructible_v<std::ranges::in_value_result<C, C>, std::ranges::in_value_result<int, int>&>);
// has to be convertible via const&
static_assert(std::is_convertible_v<std::ranges::in_value_result<int, int>&, std::ranges::in_value_result<long, long>>);
static_assert(
std::is_convertible_v<const std::ranges::in_value_result<int, int>&, std::ranges::in_value_result<long, long>>);
static_assert(
std::is_convertible_v<std::ranges::in_value_result<int, int>&&, std::ranges::in_value_result<long, long>>);
static_assert(
std::is_convertible_v<const std::ranges::in_value_result<int, int>&&, std::ranges::in_value_result<long, long>>);
// should be move constructible
static_assert(std::is_move_constructible_v<std::ranges::in_value_result<MoveOnly, int>>);
static_assert(std::is_move_constructible_v<std::ranges::in_value_result<int, MoveOnly>>);
// should not copy constructible with move-only type
static_assert(!std::is_copy_constructible_v<std::ranges::in_value_result<MoveOnly, int>>);
static_assert(!std::is_copy_constructible_v<std::ranges::in_value_result<int, MoveOnly>>);
struct NotConvertible {};
// conversions should not work if there is no conversion
static_assert(
!std::is_convertible_v<std::ranges::in_value_result<NotConvertible, int>, std::ranges::in_value_result<int, int>>);
static_assert(
!std::is_convertible_v<std::ranges::in_value_result<int, NotConvertible>, std::ranges::in_value_result<int, int>>);
template <class T>
struct ConvertibleFrom {
constexpr ConvertibleFrom(T c) : content{c} {}
T content;
};
constexpr bool test() {
{
std::ranges::in_value_result<int, double> res{10, 0.};
assert(res.in == 10);
assert(res.value == 0.);
std::ranges::in_value_result<ConvertibleFrom<int>, ConvertibleFrom<double>> res2 = res;
assert(res2.in.content == 10);
assert(res2.value.content == 0.);
}
{
std::ranges::in_value_result<MoveOnly, int> res{MoveOnly{}, 2};
assert(res.in.get() == 1);
assert(res.value == 2);
auto res2 = static_cast<std::ranges::in_value_result<MoveOnly, int>>(std::move(res));
assert(res.in.get() == 0);
assert(res2.in.get() == 1);
assert(res2.value == 2);
}
{
auto [in, value] = std::ranges::in_value_result<int, int>{1, 2};
assert(in == 1);
assert(value == 2);
}
return true;
}
int main(int, char**) {
test();
static_assert(test());
return 0;
}

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@ -53,6 +53,14 @@ static_assert(sizeof(std::ranges::in_out_out_result<Empty, Empty, char>) == 2);
static_assert(sizeof(std::ranges::in_out_out_result<int, Empty, Empty2>) == sizeof(int));
static_assert(sizeof(std::ranges::in_out_out_result<Empty, Empty, Empty>) == 3);
#if TEST_STD_VER >= 23
static_assert(sizeof(std::ranges::in_value_result<Empty, int>) == sizeof(int));
static_assert(sizeof(std::ranges::in_value_result<int, Empty>) == sizeof(int));
static_assert(sizeof(std::ranges::in_value_result<Empty, Empty2>) == sizeof(Empty2));
#endif // TEST_STD_VER
// In min_max_result both elements have the same type, so they can't have the same address.
// So the only way to test that [[no_unique_address]] is used is to have it in another struct
struct MinMaxNoUniqueAddress {

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@ -16,6 +16,8 @@
#include <memory>
#include <type_traits>
#include "test_macros.h"
using namespace std::ranges;
static_assert(std::is_same_v<in_fun_result<int, long>, for_each_result<int, long>>);
@ -59,4 +61,10 @@ static_assert(std::is_same_v<min_max_result<int>, minmax_element_result<int>>);
static_assert(std::is_same_v<in_found_result<int>, next_permutation_result<int>>);
static_assert(std::is_same_v<in_found_result<int>, prev_permutation_result<int>>);
#if TEST_STD_VER >= 23
static_assert(std::is_same_v<in_value_result<int, long>, fold_left_with_iter_result<int, long>>);
// static_assert(std::is_same_v<out_value_result<int>, iota_result<int>>);
#endif // TEST_STD_VER

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@ -81,6 +81,7 @@ struct not_indirectly_readable {
};
static_assert(!std::indirectly_readable<not_indirectly_readable> && !std::input_iterator<not_indirectly_readable>);
// FIXME(cjdb): deduplicate
struct bad_iterator_category {
using value_type = int;
using difference_type = std::ptrdiff_t;

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@ -86,6 +86,10 @@ static_assert(test(std::ranges::find_end, a, a));
static_assert(test(std::ranges::find_first_of, a, a));
static_assert(test(std::ranges::find_if, a, odd));
static_assert(test(std::ranges::find_if_not, a, odd));
#if TEST_STD_VER >= 23
static_assert(test(std::ranges::fold_left, a, 0, std::plus()));
static_assert(test(std::ranges::fold_left_with_iter, a, 0, std::plus()));
#endif
static_assert(test(std::ranges::for_each, a, odd));
static_assert(test(std::ranges::for_each_n, a, 10, odd));
static_assert(test(std::ranges::generate, a, gen));

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@ -15,6 +15,6 @@
#include "test_range.h"
static_assert(std::ranges::borrowed_range<std::ranges::ref_view<BorrowedRange>>);
static_assert(std::ranges::borrowed_range<std::ranges::ref_view<BorrowedRange<>>>);
static_assert(std::ranges::borrowed_range<std::ranges::ref_view<BorrowedView>>);
static_assert(std::ranges::borrowed_range<std::ranges::ref_view<NonBorrowedView>>);

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@ -0,0 +1,89 @@
//===----------------------------------------------------------------------===//
//
// 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 TEST_SUPPORT_INVOCABLE_WITH_TELEMETRY_H
#define TEST_SUPPORT_INVOCABLE_WITH_TELEMETRY_H
#include <cassert>
#include <concepts>
#include <functional>
#include <utility>
#if TEST_STD_VER < 20
# error invocable_with_telemetry requires C++20
#else
struct invocable_telemetry {
int invocations;
int moves;
int copies;
};
template <class F>
class invocable_with_telemetry {
public:
constexpr invocable_with_telemetry(F f, invocable_telemetry& telemetry) : f_(f), telemetry_(&telemetry) {}
constexpr invocable_with_telemetry(invocable_with_telemetry&& other)
requires std::move_constructible<F>
: f_(std::move(other.f_)),
telemetry_(assert(other.telemetry_ != nullptr), std::exchange(other.telemetry_, nullptr)) {
++telemetry_->moves;
}
constexpr invocable_with_telemetry(invocable_with_telemetry const& other)
requires std::copy_constructible<F>
: f_(other.f_), telemetry_((assert(other.telemetry_ != nullptr), other.telemetry_)) {
++telemetry_->copies;
}
constexpr invocable_with_telemetry& operator=(invocable_with_telemetry&& other)
requires std::movable<F>
{
// Not using move-and-swap idiom to ensure that copies and moves remain accurate.
assert(&other != this);
assert(other.telemetry_ != nullptr);
f_ = std::move(other.f_);
telemetry_ = std::exchange(other.telemetry_, nullptr);
++telemetry_->moves;
return *this;
}
constexpr invocable_with_telemetry& operator=(invocable_with_telemetry const& other)
requires std::copyable<F>
{
// Not using copy-and-swap idiom to ensure that copies and moves remain accurate.
assert(&other != this);
assert(other.telemetry_ != nullptr);
f_ = other.f_;
telemetry_ = other.telemetry_;
++telemetry_->copies;
return *this;
}
template <class... Args>
requires std::invocable<F&, Args...>
constexpr decltype(auto) operator()(Args&&... args) noexcept(std::is_nothrow_invocable_v<F&, Args...>) {
assert(telemetry_);
++telemetry_->invocations;
return std::invoke(f_, std::forward<Args>(args)...);
}
private:
F f_ = F();
invocable_telemetry* telemetry_ = nullptr;
};
template <class F>
invocable_with_telemetry(F f, int& invocations, int& moves, int& copies) -> invocable_with_telemetry<F>;
#endif // TEST_STD_VER < 20
#endif // TEST_SUPPORT_INVOCABLE_WITH_TELEMETRY_H

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@ -0,0 +1,68 @@
//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
// Implementations of well-known functions in mathematics that are useful for
// testing algorithms.
#ifndef LIBCXX_TEST_MATHS_H
#define LIBCXX_TEST_MATHS_H
#include <algorithm>
#include <cassert>
#include <concepts>
#include <ranges>
#include <vector>
template <std::ranges::forward_range R>
constexpr std::ranges::range_value_t<R> triangular_sum(R& input) {
assert(not std::ranges::empty(input));
auto [min, max] = std::ranges::minmax_element(input);
return static_cast<std::ranges::range_value_t<R>>(
(static_cast<double>(std::ranges::distance(input)) / 2) * (*min + *max));
}
template <std::integral I>
constexpr I factorial(I const n) {
assert(n >= 0);
auto result = I(1);
for (auto i = I(1); i <= n; ++i) {
result *= i;
}
return result;
}
static_assert(factorial(0) == 1);
static_assert(factorial(1) == 1);
static_assert(factorial(2) == 2);
static_assert(factorial(3) == 6);
static_assert(factorial(4) == 24);
static_assert(factorial(5) == 120);
template <std::integral I>
constexpr I fibonacci(I const n) {
assert(n >= 0);
auto result = I(0);
auto prev = I(1);
for (auto i = I(0); i < n; ++i) {
result += std::exchange(prev, result);
}
return result;
}
static_assert(fibonacci(0) == 0);
static_assert(fibonacci(1) == 1);
static_assert(fibonacci(2) == 1);
static_assert(fibonacci(3) == 2);
static_assert(fibonacci(4) == 3);
static_assert(fibonacci(5) == 5);
static_assert(fibonacci(6) == 8);
static_assert(fibonacci(7) == 13);
static_assert(fibonacci(8) == 21);
static_assert(fibonacci(9) == 34);
#endif // LIBCXX_TEST_MATHS_H

View File

@ -15,62 +15,64 @@
#include "test_iterators.h"
#if TEST_STD_VER < 17
#error "test/support/test_range.h" can only be included in builds supporting ranges
# error "test/support/test_range.h" can only be included in builds supporting ranges
#endif
struct sentinel {
bool operator==(std::input_or_output_iterator auto const&) const;
};
template <template <class...> class I>
requires std::input_or_output_iterator<I<int*> >
template <template <class...> class I, class T = int>
requires std::input_or_output_iterator<I<T*> >
struct test_range {
I<int*> begin();
I<int const*> begin() const;
I<T*> begin();
I<T const*> begin() const;
sentinel end();
sentinel end() const;
};
template <template <class...> class I>
requires std::input_or_output_iterator<I<int*> >
template <template <class...> class I, class T = int>
requires std::input_or_output_iterator<I<T*> >
struct test_non_const_range {
I<int*> begin();
I<T*> begin();
sentinel end();
};
template <template <class...> class I>
requires std::input_or_output_iterator<I<int*> >
template <template <class...> class I, class T = int>
requires std::input_or_output_iterator<I<T*> >
struct test_common_range {
I<int*> begin();
I<int const*> begin() const;
I<int*> end();
I<int const*> end() const;
I<T*> begin();
I<T const*> begin() const;
I<T*> end();
I<T const*> end() const;
};
template <template <class...> class I>
requires std::input_or_output_iterator<I<int*> >
template <template <class...> class I, class T = int>
requires std::input_or_output_iterator<I<T*> >
struct test_non_const_common_range {
I<int*> begin();
I<int*> end();
I<T*> begin();
I<T*> end();
};
template <template <class...> class I>
requires std::input_or_output_iterator<I<int*> >
template <template <class...> class I, class T = int>
requires std::input_or_output_iterator<I<T*> >
struct test_view : std::ranges::view_base {
I<int*> begin();
I<int const*> begin() const;
I<T*> begin();
I<T const*> begin() const;
sentinel end();
sentinel end() const;
};
template <class T = int>
struct BorrowedRange {
int *begin() const;
int *end() const;
T* begin() const;
T* end() const;
BorrowedRange(BorrowedRange&&) = delete;
};
template<> inline constexpr bool std::ranges::enable_borrowed_range<BorrowedRange> = true;
static_assert(!std::ranges::view<BorrowedRange>);
static_assert(std::ranges::borrowed_range<BorrowedRange>);
template <class T>
inline constexpr bool std::ranges::enable_borrowed_range<BorrowedRange<T>> = true;
static_assert(!std::ranges::view<BorrowedRange<>>);
static_assert(std::ranges::borrowed_range<BorrowedRange<>>);
using BorrowedView = std::ranges::empty_view<int>;
static_assert(std::ranges::view<BorrowedView>);