libcxx/test/std/containers/sequences/array/front_back_const.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 // const_reference front() const; // constexpr in C++14
  12 // const_reference back() const;  // constexpr in C++14
  13
  14 #include <array>
  15 #include <cassert>
  16
  17 #include "test_macros.h"
  18
  19 // std::array is explicitly allowed to be initialized with A a = { init-list };.
  20 // Disable the missing braces warning for this reason.
  21 #include "disable_missing_braces_warning.h"
  22
  23
  24 TEST_CONSTEXPR_CXX14 bool tests()
  25 {
  26     {
  27         typedef double T;
  28         typedef std::array<T, 3> C;
  29         C const c = {1, 2, 3.5};
  30         C::const_reference r1 = c.front();
  31         assert(r1 == 1);
  32
  33         C::const_reference r2 = c.back();
  34         assert(r2 == 3.5);
  35     }
  36     {
  37         typedef double T;
  38         typedef std::array<T, 0> C;
  39         C const c = {};
  40         ASSERT_SAME_TYPE(decltype(c.back()), C::const_reference);
  41         LIBCPP_ASSERT_NOEXCEPT(c.back());
  42         ASSERT_SAME_TYPE(decltype(c.front()), C::const_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 const c = {};
  53         ASSERT_SAME_TYPE(decltype(c.back()), C::const_reference);
  54         LIBCPP_ASSERT_NOEXCEPT(c.back());
  55         ASSERT_SAME_TYPE(decltype(c.front()), C::const_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 >= 14
  70     static_assert(tests(), "");
  71 #endif
  72     return 0;
  73 }