libcxx/test/std/containers/sequences/array/front_back.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 // <array>
  10
  11 // reference front();  // constexpr in C++17
  12 // reference back();   // constexpr in C++17
  13
  14 #include <array>
  15 #include <cassert>
  16
  17 #include "test_macros.h"
  18
  19 TEST_CONSTEXPR_CXX17 bool tests()
  20 {
  21     {
  22         typedef double T;
  23         typedef std::array<T, 3> C;
  24         C c = {1, 2, 3.5};
  25
  26         C::reference r1 = c.front();
  27         assert(r1 == 1);
  28         r1 = 5.5;
  29         assert(c[0] == 5.5);
  30
  31         C::reference r2 = c.back();
  32         assert(r2 == 3.5);
  33         r2 = 7.5;
  34         assert(c[2] == 7.5);
  35     }
  36     {
  37         typedef double T;
  38         typedef std::array<T, 0> C;
  39         C c = {};
  40         ASSERT_SAME_TYPE(decltype(c.back()), C::reference);
  41         LIBCPP_ASSERT_NOEXCEPT(c.back());
  42         ASSERT_SAME_TYPE(decltype(c.front()), C::reference);
  43         LIBCPP_ASSERT_NOEXCEPT(c.front());
  44         if (c.size() > (0)) { // always false
  45             TEST_IGNORE_NODISCARD c.front();
  46             TEST_IGNORE_NODISCARD c.back();
  47         }
  48     }
  49     {
  50         typedef double T;
  51         typedef std::array<const T, 0> C;
  52         C c = {};
  53         ASSERT_SAME_TYPE(decltype( c.back()), C::reference);
  54         LIBCPP_ASSERT_NOEXCEPT(    c.back());
  55         ASSERT_SAME_TYPE(decltype( c.front()), C::reference);
  56         LIBCPP_ASSERT_NOEXCEPT(    c.front());
  57         if (c.size() > (0)) {
  58             TEST_IGNORE_NODISCARD c.front();
  59             TEST_IGNORE_NODISCARD c.back();
  60         }
  61     }
  62
  63     return true;
  64 }
  65
  66 int main(int, char**)
  67 {
  68     tests();
  69 #if TEST_STD_VER >= 17
  70     static_assert(tests(), "");
  71 #endif
  72     return 0;
  73 }