libcxx/test/std/ranges/range.adaptors/range.stride.view/concept.compile.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

// template <input_range V> requires view<V>

#include <ranges>
#include <type_traits>

#include "almost_satisfies_types.h"
#include "test_iterators.h"
#include "test_range.h"

template <typename I, std::ranges::range_difference_t<I> D>
concept CanStrideView = requires { std::ranges::stride_view<I>{I{}, D}; };

// Ensure that the InputRangeNotIndirectlyReadable is a valid range.
static_assert(std::ranges::range<InputRangeNotIndirectlyReadable>);
// Ensure that the InputRangeNotIndirectlyReadable's iterator is not an input range ...
static_assert(!std::ranges::input_range<std::ranges::iterator_t<InputRangeNotIndirectlyReadable>>);
// Because CanStrideView requires that the range/view type be default constructible, let's double check that ...
static_assert(std::is_default_constructible_v<InputRangeNotIndirectlyReadable>);
// And now, finally, let's make sure that we cannot stride over a range whose iterator is not an input iterator ...
static_assert(!CanStrideView<InputRangeNotIndirectlyReadable, 1>);

// Ensure that a range that is not a view cannot be the subject of a stride_view.
static_assert(std::ranges::range<test_non_const_range<cpp17_input_iterator>>);
static_assert(std::ranges::input_range<test_non_const_range<cpp17_input_iterator>>);
static_assert(std::movable<test_non_const_range<cpp17_input_iterator>>);
static_assert(!std::ranges::view<test_non_const_range<cpp17_input_iterator>>);
static_assert(!CanStrideView<test_non_const_range<cpp17_input_iterator>, 1>);

// And now, let's satisfy all the prerequisites and make sure that we can stride over a range (that is an input range
// and is a view!)
static_assert(std::ranges::range<test_view<cpp17_input_iterator>>);
static_assert(std::ranges::input_range<test_view<cpp17_input_iterator>>);
static_assert(std::ranges::view<test_view<cpp17_input_iterator>>);
static_assert(CanStrideView<test_view<cpp17_input_iterator>, 1>);

// stride_view itself models view.
static_assert(std::ranges::view<std::ranges::stride_view<test_view<cpp17_input_iterator>>>);
static_assert(std::ranges::view<std::ranges::stride_view<test_view<forward_iterator>>>);