1 //===----------------------------------------------------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is dual licensed under the MIT and the University of Illinois Open
6 // Source Licenses. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9
10 // <iterator>
11
12 // reverse_iterator
13
14 // template <RandomAccessIterator Iter1, RandomAccessIterator Iter2>
15 // requires HasMinus<Iter2, Iter1>
16 // constexpr auto operator-(const reverse_iterator<Iter1>& x, const reverse_iterator<Iter2>& y)
17 // -> decltype(y.base() - x.base());
18 //
19 // constexpr in C++17
20
21 #include <iterator>
22 #include <cstddef>
23 #include <cassert>
24
25 #include "test_macros.h"
26 #include "test_iterators.h"
27
28 template <class It1, class It2>
29 void
test(It1 l,It2 r,std::ptrdiff_t x)30 test(It1 l, It2 r, std::ptrdiff_t x)
31 {
32 const std::reverse_iterator<It1> r1(l);
33 const std::reverse_iterator<It2> r2(r);
34 assert((r1 - r2) == x);
35 }
36
main()37 int main()
38 {
39 char s[3] = {0};
40 test(random_access_iterator<const char*>(s), random_access_iterator<char*>(s), 0);
41 test(random_access_iterator<char*>(s), random_access_iterator<const char*>(s+1), 1);
42 test(random_access_iterator<const char*>(s+1), random_access_iterator<char*>(s), -1);
43 test(s, s, 0);
44 test(s, s+1, 1);
45 test(s+1, s, -1);
46
47 #if TEST_STD_VER > 14
48 {
49 constexpr const char *p = "123456789";
50 typedef std::reverse_iterator<const char *> RI;
51 constexpr RI it1 = std::make_reverse_iterator(p);
52 constexpr RI it2 = std::make_reverse_iterator(p+1);
53 static_assert( it1 - it2 == 1, "");
54 static_assert( it2 - it1 == -1, "");
55 }
56 #endif
57 }
58