test/std/iterators/predef.iterators/reverse.iterators/reverse.iter.ops/reverse.iter.op+/difference_type.pass.cpp

   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 // requires RandomAccessIterator<Iter>
  15 //   constexpr reverse_iterator operator+(difference_type n) const;
  16 //
  17 // constexpr in c++17
  18
  19 #include <iterator>
  20 #include <cassert>
  21
  22 #include "test_macros.h"
  23 #include "test_iterators.h"
  24
  25 template <class It>
  26 void
  27 test(It i, typename std::iterator_traits<It>::difference_type n, It x)
  28 {
  29     const std::reverse_iterator<It> r(i);
  30     std::reverse_iterator<It> rr = r + n;
  31     assert(rr.base() == x);
  32 }
  33
  34 int main()
  35 {
  36     const char* s = "1234567890";
  37     test(random_access_iterator<const char*>(s+5), 5, random_access_iterator<const char*>(s));
  38     test(s+5, 5, s);
  39
  40 #if TEST_STD_VER > 14
  41     {
  42         constexpr const char *p = "123456789";
  43         typedef std::reverse_iterator<const char *> RI;
  44         constexpr RI it1 = std::make_reverse_iterator(p);
  45         constexpr RI it2 = std::make_reverse_iterator(p + 5);
  46         constexpr RI it3 = it2 + 5;
  47         static_assert(it1 != it2, "");
  48         static_assert(it1 == it3, "");
  49         static_assert(it2 != it3, "");
  50     }
  51 #endif
  52 }