llvm/libcxx/test/std/containers/views/mdspan/layout_left/ctor.extents.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

// <mdspan>

// constexpr mapping(const extents_type&) noexcept;
//
// Preconditions: The size of the multidimensional index space e is representable
//                as a value of type index_type ([basic.fundamental]).
//
// Effects: Direct-non-list-initializes extents_ with e.

#include <mdspan>
#include <cassert>
#include <cstdint>
#include <span> // dynamic_extent

#include "test_macros.h"

template <class E>
constexpr void test_construction(E e) {
  using M = std::layout_left::mapping<E>;
  ASSERT_NOEXCEPT(M{e});
  M m(e);

  // check correct extents are returned
  ASSERT_NOEXCEPT(m.extents());
  assert(m.extents() == e);

  // check required_span_size()
  typename E::index_type expected_size = 1;
  for (typename E::rank_type r = 0; r < E::rank(); r++)
    expected_size *= e.extent(r);
  assert(m.required_span_size() == expected_size);
}

constexpr bool test() {
  constexpr size_t D = std::dynamic_extent;
  test_construction(std::extents<int>());
  test_construction(std::extents<unsigned, D>(7));
  test_construction(std::extents<unsigned, 7>());
  test_construction(std::extents<unsigned, 7, 8>());
  test_construction(std::extents<int64_t, D, 8, D, D>(7, 9, 10));
  return true;
}

int main(int, char**) {
  test();
  static_assert(test());
  return 0;
}