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// UNSUPPORTED: c++03, c++11, c++14, c++17
9
10// <span>
11
12// constexpr reference front() const noexcept;
13// Expects: empty() is false.
14// Effects: Equivalent to: return *data();
15//
16
17#include <span>
18#include <cassert>
19#include <string>
20
21#include "test_macros.h"
22
23template <typename Span>
24constexpr bool testConstexprSpan(Span sp) {
25 LIBCPP_ASSERT(noexcept(sp.front()));
26 return std::addressof(sp.front()) == sp.data();
27}
28
29template <typename Span>
30void testRuntimeSpan(Span sp) {
31 LIBCPP_ASSERT(noexcept(sp.front()));
32 assert(std::addressof(sp.front()) == sp.data());
33}
34
35template <typename Span>
36void testEmptySpan(Span sp) {
37 if (!sp.empty()) [[maybe_unused]]
38 auto res = sp.front();
39}
40
41struct A {};
42constexpr int iArr1[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
43int iArr2[] = {10, 11, 12, 13, 14, 15, 16, 17, 18, 19};
44
45int main(int, char**) {
46 static_assert(testConstexprSpan(std::span<const int>(iArr1, 1)), "");
47 static_assert(testConstexprSpan(std::span<const int>(iArr1, 2)), "");
48 static_assert(testConstexprSpan(std::span<const int>(iArr1, 3)), "");
49 static_assert(testConstexprSpan(std::span<const int>(iArr1, 4)), "");
50
51 static_assert(testConstexprSpan(std::span<const int, 1>(iArr1, 1)), "");
52 static_assert(testConstexprSpan(std::span<const int, 2>(iArr1, 2)), "");
53 static_assert(testConstexprSpan(std::span<const int, 3>(iArr1, 3)), "");
54 static_assert(testConstexprSpan(std::span<const int, 4>(iArr1, 4)), "");
55
56 testRuntimeSpan(std::span<int>(iArr2, 1));
57 testRuntimeSpan(std::span<int>(iArr2, 2));
58 testRuntimeSpan(std::span<int>(iArr2, 3));
59 testRuntimeSpan(std::span<int>(iArr2, 4));
60
61 testRuntimeSpan(std::span<int, 1>(iArr2, 1));
62 testRuntimeSpan(std::span<int, 2>(iArr2, 2));
63 testRuntimeSpan(std::span<int, 3>(iArr2, 3));
64 testRuntimeSpan(std::span<int, 4>(iArr2, 4));
65
66 std::string s;
67 testRuntimeSpan(std::span<std::string>(&s, 1));
68 testRuntimeSpan(std::span<std::string, 1>(&s, 1));
69
70 std::span<int, 0> sp;
71 testEmptySpan(sp);
72
73 return 0;
74}
75

source code of libcxx/test/std/containers/views/views.span/span.elem/front.pass.cpp