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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
// constexpr auto begin();
#include <array>
#include <cassert>
#include <ranges>
#include <type_traits>
#include <utility>
#include "test_iterators.h"
struct View : std::ranges::view_base {
int* begin() const;
int* end() const;
};
// Test that begin is not const
template <class T>
concept HasBegin = requires(T t) { t.begin(); };
struct Pred {
constexpr bool operator()(int i) const { return i < 3; }
};
static_assert(HasBegin<std::ranges::drop_while_view<View, Pred>>);
static_assert(!HasBegin<const std::ranges::drop_while_view<View, Pred>>);
constexpr auto always = [](auto v) { return [v](auto&&...) { return v; }; };
template <class Iter>
constexpr void testOne() {
using Sent = sentinel_wrapper<Iter>;
using Range = std::ranges::subrange<Iter, Sent>;
constexpr auto make_subrange = []<std::size_t N>(int(&buffer)[N]) {
return Range{Iter{buffer}, Sent{Iter{buffer + N}}};
};
// empty
{
std::array<int, 0> a;
Range range{Iter{a.data()}, Sent{Iter{a.data() + a.size()}}};
std::ranges::drop_while_view dwv{std::move(range), always(false)};
std::same_as<Iter> decltype(auto) it = dwv.begin();
assert(base(it) == a.data() + a.size());
}
// 1 element not dropped
{
int buffer[] = {1};
auto range = make_subrange(buffer);
std::ranges::drop_while_view dwv{std::move(range), always(false)};
std::same_as<Iter> decltype(auto) it = dwv.begin();
assert(base(it) == buffer);
}
// 1 element dropped
{
int buffer[] = {1};
auto range = make_subrange(buffer);
std::ranges::drop_while_view dwv{std::move(range), always(true)};
std::same_as<Iter> decltype(auto) it = dwv.begin();
assert(base(it) == buffer + 1);
}
// multiple elements. no element dropped
{
int buffer[] = {1, 2, 3, 4, 5};
auto range = make_subrange(buffer);
std::ranges::drop_while_view dwv{std::move(range), always(false)};
std::same_as<Iter> decltype(auto) it = dwv.begin();
assert(base(it) == buffer);
}
// multiple elements. all elements dropped
{
int buffer[] = {1, 2, 3, 4, 5};
auto range = make_subrange(buffer);
std::ranges::drop_while_view dwv{std::move(range), always(true)};
std::same_as<Iter> decltype(auto) it = dwv.begin();
assert(base(it) == buffer + 5);
}
// multiple elements. some elements dropped
{
int buffer[] = {1, 2, 3, 2, 1};
auto range = make_subrange(buffer);
std::ranges::drop_while_view dwv{std::move(range), [](int i) { return i < 3; }};
std::same_as<Iter> decltype(auto) it = dwv.begin();
assert(base(it) == buffer + 2);
}
// Make sure we do not make a copy of the predicate when we call begin()
{
struct TrackingPred {
constexpr explicit TrackingPred(bool* moved, bool* copied) : moved_(moved), copied_(copied) {}
constexpr TrackingPred(TrackingPred const& other) : moved_(other.moved_), copied_(other.copied_) {
*copied_ = true;
}
constexpr TrackingPred(TrackingPred&& other) : moved_(other.moved_), copied_(other.copied_) { *moved_ = true; }
TrackingPred& operator=(TrackingPred const&) = default;
TrackingPred& operator=(TrackingPred&&) = default;
constexpr bool operator()(int i) const { return i < 3; }
bool* moved_;
bool* copied_;
};
int buffer[] = {1, 2, 3, 2, 1};
bool moved = false, copied = false;
auto range = make_subrange(buffer);
std::ranges::drop_while_view dwv{std::move(range), TrackingPred(&moved, &copied)};
moved = false;
copied = false;
[[maybe_unused]] auto it = dwv.begin();
assert(!moved);
assert(!copied);
}
// Test with a non-const predicate
{
int buffer[] = {1, 2, 3, 2, 1};
auto range = make_subrange(buffer);
std::ranges::drop_while_view dwv{std::move(range), [](int i) mutable { return i < 3; }};
std::same_as<Iter> decltype(auto) it = dwv.begin();
assert(base(it) == buffer + 2);
}
// Test with a predicate that takes by non-const reference
{
int buffer[] = {1, 2, 3, 2, 1};
auto range = make_subrange(buffer);
std::ranges::drop_while_view dwv{std::move(range), [](int& i) { return i < 3; }};
std::same_as<Iter> decltype(auto) it = dwv.begin();
assert(base(it) == buffer + 2);
}
if constexpr (std::forward_iterator<Iter>) {
// Make sure that we cache the result of begin() on subsequent calls
{
int buffer[] = {1, 2, 3, 2, 1};
auto range = make_subrange(buffer);
int called = 0;
auto pred = [&](int i) {
++called;
return i < 3;
};
std::ranges::drop_while_view dwv{range, pred};
for (auto i = 0; i < 10; ++i) {
std::same_as<Iter> decltype(auto) it = dwv.begin();
assert(base(it) == buffer + 2);
assert(called == 3);
}
}
}
}
constexpr bool test() {
testOne<cpp17_input_iterator<int*>>();
testOne<cpp20_input_iterator<int*>>();
testOne<forward_iterator<int*>>();
testOne<bidirectional_iterator<int*>>();
testOne<random_access_iterator<int*>>();
testOne<contiguous_iterator<int*>>();
testOne<int*>();
return true;
}
int main(int, char**) {
test();
static_assert(test());
return 0;
}
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