libcxx/test/std/ranges/range.factories/range.single.view/empty.pass.cpp

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 // UNSUPPORTED: c++03, c++11, c++14, c++17
  10
  11 // static constexpr bool empty() noexcept;
  12
  13 #include <cassert>
  14 #include <concepts>
  15 #include <ranges>
  16 #include <utility>
  17
  18 #include "test_macros.h"
  19
  20 struct Empty {};
  21 struct BigType {
  22   char buffer[64] = {10};
  23 };
  24
  25 template <typename T>
  26 constexpr void test_empty(T value) {
  27   using SingleView = std::ranges::single_view<T>;
  28
  29   {
  30     std::same_as<bool> decltype(auto) result = SingleView::empty();
  31     assert(result == false);
  32     static_assert(noexcept(SingleView::empty()));
  33   }
  34
  35   {
  36     SingleView sv{value};
  37
  38     std::same_as<bool> decltype(auto) result = std::ranges::empty(sv);
  39     assert(result == false);
  40     static_assert(noexcept(std::ranges::empty(sv)));
  41   }
  42   {
  43     const SingleView sv{value};
  44
  45     std::same_as<bool> decltype(auto) result = std::ranges::empty(sv);
  46     assert(result == false);
  47     static_assert(noexcept(std::ranges::empty(std::as_const(sv))));
  48   }
  49 }
  50
  51 constexpr bool test() {
  52   test_empty<int>(92);
  53   test_empty<Empty>(Empty{});
  54   test_empty<BigType>(BigType{});
  55
  56   return true;
  57 }
  58
  59 int main(int, char**) {
  60   test();
  61   static_assert(test());
  62
  63   return 0;
  64 }