test/std/containers/sequences/array/front_back.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
//
//===----------------------------------------------------------------------===//

// <array>

// reference front();  // constexpr in C++17
// reference back();   // constexpr in C++17

#include <array>
#include <cassert>

#include "test_macros.h"

// std::array is explicitly allowed to be initialized with A a = { init-list };.
// Disable the missing braces warning for this reason.
#include "disable_missing_braces_warning.h"


TEST_CONSTEXPR_CXX17 bool tests()
{
    {
        typedef double T;
        typedef std::array<T, 3> C;
        C c = {1, 2, 3.5};

        C::reference r1 = c.front();
        assert(r1 == 1);
        r1 = 5.5;
        assert(c[0] == 5.5);

        C::reference r2 = c.back();
        assert(r2 == 3.5);
        r2 = 7.5;
        assert(c[2] == 7.5);
    }
    {
        typedef double T;
        typedef std::array<T, 0> C;
        C c = {};
        ASSERT_SAME_TYPE(decltype(c.back()), C::reference);
        LIBCPP_ASSERT_NOEXCEPT(c.back());
        ASSERT_SAME_TYPE(decltype(c.front()), C::reference);
        LIBCPP_ASSERT_NOEXCEPT(c.front());
        if (c.size() > (0)) { // always false
            TEST_IGNORE_NODISCARD c.front();
            TEST_IGNORE_NODISCARD c.back();
        }
    }
    {
        typedef double T;
        typedef std::array<const T, 0> C;
        C c = {};
        ASSERT_SAME_TYPE(decltype( c.back()), C::reference);
        LIBCPP_ASSERT_NOEXCEPT(    c.back());
        ASSERT_SAME_TYPE(decltype( c.front()), C::reference);
        LIBCPP_ASSERT_NOEXCEPT(    c.front());
        if (c.size() > (0)) {
            TEST_IGNORE_NODISCARD c.front();
            TEST_IGNORE_NODISCARD c.back();
        }
    }

    return true;
}

int main(int, char**)
{
    tests();
#if TEST_STD_VER >= 17
    static_assert(tests(), "");
#endif
    return 0;
}