llvm/libcxx/test/std/ranges/range.adaptors/range.zip/iterator/subscript.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, c++20

// constexpr auto operator[](difference_type n) const requires
//        all_random_access<Const, Views...>

#include <ranges>
#include <cassert>

#include "../types.h"

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

  {
    // random_access_range
    std::ranges::zip_view v(SizedRandomAccessView{buffer}, std::views::iota(0));
    auto it = v.begin();
    assert(it[0] == *it);
    assert(it[2] == *(it + 2));
    assert(it[4] == *(it + 4));

#ifdef _LIBCPP_VERSION // libc++ doesn't implement P2165R4 yet
    static_assert(std::is_same_v<decltype(it[2]), std::pair<int&, int>>);
#else
    static_assert(std::is_same_v<decltype(it[2]), std::tuple<int&, int>>);
#endif
  }

  {
    // contiguous_range
    std::ranges::zip_view v(ContiguousCommonView{buffer}, ContiguousCommonView{buffer});
    auto it = v.begin();
    assert(it[0] == *it);
    assert(it[2] == *(it + 2));
    assert(it[4] == *(it + 4));

#ifdef _LIBCPP_VERSION // libc++ doesn't implement P2165R4 yet
    static_assert(std::is_same_v<decltype(it[2]), std::pair<int&, int&>>);
#else
    static_assert(std::is_same_v<decltype(it[2]), std::tuple<int&, int&>>);
#endif
  }

  {
    // non random_access_range
    std::ranges::zip_view v(BidiCommonView{buffer});
    auto iter = v.begin();
    const auto canSubscript = [](auto&& it) { return requires { it[0]; }; };
    static_assert(!canSubscript(iter));
  }

  return true;
}

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

  return 0;
}