third_party/llvm-project/libcxx/test/std/ranges/range.factories/range.iota.view/sentinel/minus.pass.cpp

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

// friend constexpr iter_difference_t<W> operator-(const iterator& x, const sentinel& y)
//   requires sized_sentinel_for<Bound, W>;
// friend constexpr iter_difference_t<W> operator-(const sentinel& x, const iterator& y)
//   requires sized_sentinel_for<Bound, W>;

#include <ranges>
#include <cassert>

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

template<class T>
concept MinusInvocable = requires(std::ranges::iota_view<T, IntSentinelWith<T>> io) {
  io.end() - io.begin();
};

constexpr bool test() {
  int buffer[8] = {1, 2, 3, 4, 5, 6, 7, 8};

  {
    auto outIter = random_access_iterator<int*>(buffer);
    std::ranges::iota_view<random_access_iterator<int*>, IntSentinelWith<random_access_iterator<int*>>> io(
      outIter, IntSentinelWith<random_access_iterator<int*>>(std::ranges::next(outIter, 8)));
    auto iter = io.begin();
    auto sent = io.end();
    assert(iter - sent == -8);
    assert(sent - iter == 8);
  }
  {
    auto outIter = random_access_iterator<int*>(buffer);
    const std::ranges::iota_view<random_access_iterator<int*>, IntSentinelWith<random_access_iterator<int*>>> io(
      outIter, IntSentinelWith<random_access_iterator<int*>>(std::ranges::next(outIter, 8)));
    const auto iter = io.begin();
    const auto sent = io.end();
    assert(iter - sent == -8);
    assert(sent - iter == 8);
  }

  {
    // The minus operator requires that "W" is an input_or_output_iterator.
    static_assert(!MinusInvocable<int>);
  }

  return true;
}

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

  return 0;
}