xref: /llvm-project/libcxx/test/std/ranges/range.adaptors/range.chunk.by/range.chunk.by.iter/decrement.pass.cpp (revision 8c0a61125e52b137e45131773ec08bab3e2593e4)

//===----------------------------------------------------------------------===//
//
// 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

// <ranges>

// constexpr iterator& operator--();
// constexpr iterator operator--(int);

#include <ranges>

#include <array>
#include <cassert>
#include <concepts>
#include <functional>
#include <span>
#include <type_traits>
#include <utility>

#include "../types.h"
#include "test_iterators.h"
#include "test_macros.h"

template <class T>
concept HasPreDecrement = requires(T t) {
  { --t };
};

template <class T>
concept HasPostDecrement = requires(T t) {
  { t-- };
};

struct TrackingPred : TrackInitialization {
  using TrackInitialization::TrackInitialization;
  constexpr bool operator()(int x, int y) const { return x <= y; }
};

template <class Iter, IsConst Constant, class Sent = sentinel_wrapper<Iter>>
constexpr void test() {
  using Underlying      = View<Iter, Sent>;
  using ChunkByView     = std::ranges::chunk_by_view<Underlying, std::ranges::less_equal>;
  using ChunkByIterator = std::ranges::iterator_t<ChunkByView>;

  static_assert(HasPostDecrement<ChunkByIterator>);
  static_assert(HasPreDecrement<ChunkByIterator>);

  auto make_chunk_by_view = [](auto& arr) {
    View view{Iter{arr.data()}, Sent{Iter{arr.data() + arr.size()}}};
    return ChunkByView{std::move(view), std::ranges::less_equal{}};
  };

  // Test with a single chunk
  {
    std::array array{0, 1, 2, 3, 4};
    ChunkByView view   = make_chunk_by_view(array);
    ChunkByIterator it = std::ranges::next(view.begin(), view.end());

    std::same_as<ChunkByIterator&> decltype(auto) result = --it;
    assert(&result == &it);
    assert(base((*result).begin()) == array.data());
  }

  // Test with two chunks
  {
    std::array array{0, 1, 2, 0, 1, 2};
    ChunkByView view   = make_chunk_by_view(array);
    ChunkByIterator it = std::ranges::next(view.begin(), view.end());

    std::same_as<ChunkByIterator&> decltype(auto) result = --it;
    assert(&result == &it);
    assert(base((*result).begin()) == array.data() + 3);

    --it;
    assert(base((*result).begin()) == array.data());
  }

  // Test going forward and then backward on the same iterator
  {
    std::array array{7, 8, 9, 4, 5, 6, 1, 2, 3, 0};
    ChunkByView view   = make_chunk_by_view(array);
    ChunkByIterator it = view.begin();

    ++it;
    --it;
    assert(base((*it).begin()) == array.data());
    assert(base((*it).end()) == array.data() + 3);

    ++it;
    ++it;
    --it;
    assert(base((*it).begin()) == array.data() + 3);
    assert(base((*it).end()) == array.data() + 6);

    ++it;
    ++it;
    --it;
    assert(base((*it).begin()) == array.data() + 6);
    assert(base((*it).end()) == array.data() + 9);

    ++it;
    ++it;
    --it;
    assert(base((*it).begin()) == array.data() + 9);
  }

  // Decrement an iterator multiple times
  if constexpr (std::ranges::common_range<Underlying>) {
    std::array array{1, 2, 1, 2, 1};
    ChunkByView view = make_chunk_by_view(array);

    ChunkByIterator it = view.end();
    --it;
    --it;
    --it;
    assert(base((*it).begin()) == array.data());
  }

  // Test with a predicate that takes by non-const reference
  if constexpr (!std::to_underlying(Constant)) {
    std::array array{1, 2, 3, -3, -2, -1};
    View v{Iter{array.data()}, Sent{Iter{array.data() + array.size()}}};
    auto view = std::views::chunk_by(std::move(v), [](int& x, int& y) { return x <= y; });

    auto it = std::ranges::next(view.begin());
    assert(base((*it).begin()) == array.data() + 3);
    --it;
    assert(base((*it).begin()) == array.data());
  }

  // Test with a predicate that is invocable but not callable (i.e. cannot be called like regular function 'f()')
  {
    std::array array = {1, 2, 3, -3, -2, -1};
    auto v           = View{Iter{array.data()}, Sent{Iter{array.data() + array.size()}}} |
             std::views::transform([](int x) { return IntWrapper{x}; });
    auto view = std::views::chunk_by(std::move(v), &IntWrapper::lessEqual);

    auto it = std::ranges::next(view.begin());
    assert(base((*it).begin().base()) == array.data() + 3);
    --it;
    assert(base((*it).begin().base()) == array.data());
  }

  // Make sure we do not make a copy of the predicate when we decrement
  if constexpr (std::ranges::common_range<Underlying>) {
    bool moved = false, copied = false;
    std::array array{1, 2, 1, 3};
    View v{Iter(array.data()), Sent(Iter(array.data() + array.size()))};
    auto view = std::views::chunk_by(std::move(v), TrackingPred(&moved, &copied));
    assert(std::exchange(moved, false));
    auto it = view.end();
    --it;
    it--;
    assert(!moved);
    assert(!copied);
  }

  // Check post-decrement
  {
    std::array array{0, 1, 2, -3, -2, -1, -6, -5, -4};
    ChunkByView view   = make_chunk_by_view(array);
    ChunkByIterator it = std::ranges::next(view.begin(), view.end());

    std::same_as<ChunkByIterator> decltype(auto) result = it--;
    assert(result != it);
    assert(result == std::default_sentinel);
    assert(base((*it).begin()) == array.data() + 6);

    result = it--;
    assert(base((*it).begin()) == array.data() + 3);
    assert(base((*result).begin()) == array.data() + 6);

    result = it--;
    assert(base((*it).begin()) == array.data());
    assert(base((*result).begin()) == array.data() + 3);
  }
}

template <class Iterator, IsConst Constant>
constexpr void test_with_pair() {
  // Test with pair of iterators
  test<Iterator, Constant>();

  // Test with iterator-sentinel pair
  test<Iterator, Constant, Iterator>();
}

constexpr bool tests() {
  test_with_pair<bidirectional_iterator<int*>, IsConst::no>();
  test_with_pair<random_access_iterator<int*>, IsConst::no>();
  test_with_pair<contiguous_iterator<int*>, IsConst::no>();
  test_with_pair<int*, IsConst::no>();

  test_with_pair<bidirectional_iterator<int const*>, IsConst::yes>();
  test_with_pair<random_access_iterator<int const*>, IsConst::yes>();
  test_with_pair<contiguous_iterator<int const*>, IsConst::yes>();
  test_with_pair<int const*, IsConst::yes>();

  // Make sure `operator--` isn't provided for non bidirectional ranges
  {
    using ForwardView = View<forward_iterator<int*>, sentinel_wrapper<forward_iterator<int*>>>;
    using ChunkByView = std::ranges::chunk_by_view<ForwardView, std::ranges::less_equal>;
    static_assert(!HasPreDecrement<std::ranges::iterator_t<ChunkByView>>);
    static_assert(!HasPostDecrement<std::ranges::iterator_t<ChunkByView>>);
  }

  return true;
}

int main(int, char**) {
  tests();
  static_assert(tests());

  return 0;
}