libcxx/test/std/iterators/predef.iterators/reverse.iterators/reverse.iter.nav/minus.pass.cpp

   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 // <iterator>
  10
  11 // reverse_iterator
  12
  13 // requires RandomAccessIterator<Iter>
  14 // reverse_iterator operator-(difference_type n) const; // constexpr in C++17
  15
  16 #include <iterator>
  17 #include <cassert>
  18
  19 #include "test_macros.h"
  20 #include "test_iterators.h"
  21
  22 template <class It>
  23 TEST_CONSTEXPR_CXX17 void test(It i, typename std::iterator_traits<It>::difference_type n, It x) {
  24     const std::reverse_iterator<It> r(i);
  25     std::reverse_iterator<It> rr = r - n;
  26     assert(rr.base() == x);
  27 }
  28
  29 TEST_CONSTEXPR_CXX17 bool tests() {
  30     const char* s = "1234567890";
  31     test(random_access_iterator<const char*>(s + 5), 5, random_access_iterator<const char*>(s + 10));
  32 #if TEST_STD_VER >= 20
  33     test(cpp20_random_access_iterator<const char*>(s + 5), 5, cpp20_random_access_iterator<const char*>(s + 10));
  34 #endif
  35     test(s+5, 5, s+10);
  36     return true;
  37 }
  38
  39 int main(int, char**) {
  40     tests();
  41 #if TEST_STD_VER > 14
  42     static_assert(tests(), "");
  43 #endif
  44     return 0;
  45 }