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// UNSUPPORTED: no-localization
10// UNSUPPORTED: c++03, c++11, c++14, c++17
11
12// constexpr auto begin();
13
14#include <cassert>
15#include <ranges>
16#include <sstream>
17
18#include "test_macros.h"
19#include "utils.h"
20
21template <class T>
22concept HasBegin = requires(T t) { t.begin(); };
23
24static_assert(HasBegin<std::ranges::istream_view<int>>);
25static_assert(!HasBegin<const std::ranges::istream_view<int>>);
26
27#ifndef TEST_HAS_NO_WIDE_CHARACTERS
28static_assert(HasBegin<std::ranges::wistream_view<int>>);
29static_assert(!HasBegin<const std::ranges::wistream_view<int>>);
30#endif
31
32template <class CharT>
33void test() {
34 // begin should read the first element
35 {
36 auto iss = make_string_stream<CharT>("12 3");
37 std::ranges::basic_istream_view<int, CharT> isv{iss};
38 auto it = isv.begin();
39 assert(*it == 12);
40 }
41
42 // empty stream
43 {
44 auto iss = make_string_stream<CharT>("");
45 std::ranges::basic_istream_view<int, CharT> isv{iss};
46 auto it = isv.begin();
47 assert(it == isv.end());
48 }
49}
50
51int main(int, char**) {
52 test<char>();
53#ifndef TEST_HAS_NO_WIDE_CHARACTERS
54 test<wchar_t>();
55#endif
56
57 return 0;
58}
59

source code of libcxx/test/std/ranges/range.factories/range.istream.view/begin.pass.cpp