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libcxx/test/std/containers/sequences/array/front_back.pass.cpp

120 lines
3.3 KiB
C++

//===----------------------------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// <array>
// reference front(); // constexpr in C++17
// reference back(); // constexpr in C++17
// const_reference front(); // constexpr in C++14
// const_reference back(); // constexpr in C++14
#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"
#if TEST_STD_VER > 14
constexpr bool check_front( double val )
{
std::array<double, 3> arr = {1, 2, 3.5};
return arr.front() == val;
}
constexpr bool check_back( double val )
{
std::array<double, 3> arr = {1, 2, 3.5};
return arr.back() == val;
}
#endif
int main()
{
{
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, 3> C;
const C c = {1, 2, 3.5};
C::const_reference r1 = c.front();
assert(r1 == 1);
C::const_reference r2 = c.back();
assert(r2 == 3.5);
}
{
typedef double T;
typedef std::array<T, 0> C;
C c = {};
C const& cc = c;
static_assert((std::is_same<decltype(c.front()), T &>::value), "");
static_assert((std::is_same<decltype(cc.front()), const T &>::value), "");
static_assert((std::is_same<decltype(c.back()), T &>::value), "");
static_assert((std::is_same<decltype(cc.back()), const T &>::value), "");
if (c.size() > (0)) { // always false
TEST_IGNORE_NODISCARD c.front();
TEST_IGNORE_NODISCARD c.back();
TEST_IGNORE_NODISCARD cc.front();
TEST_IGNORE_NODISCARD cc.back();
}
}
{
typedef double T;
typedef std::array<const T, 0> C;
C c = {{}};
C const& cc = c;
static_assert((std::is_same<decltype(c.front()), const T &>::value), "");
static_assert((std::is_same<decltype(cc.front()), const T &>::value), "");
static_assert((std::is_same<decltype(c.back()), const T &>::value), "");
static_assert((std::is_same<decltype(cc.back()), const T &>::value), "");
if (c.size() > (0)) {
TEST_IGNORE_NODISCARD c.front();
TEST_IGNORE_NODISCARD c.back();
TEST_IGNORE_NODISCARD cc.front();
TEST_IGNORE_NODISCARD cc.back();
}
}
#if TEST_STD_VER > 11
{
typedef double T;
typedef std::array<T, 3> C;
constexpr C c = {1, 2, 3.5};
constexpr T t1 = c.front();
static_assert (t1 == 1, "");
constexpr T t2 = c.back();
static_assert (t2 == 3.5, "");
}
#endif
#if TEST_STD_VER > 14
{
static_assert (check_front(1), "");
static_assert (check_back (3.5), "");
}
#endif
}