libcxx/test/std/iterators/predef.iterators/reverse.iterators/reverse.iter.elem/bracket.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 // unspecified operator[](difference_type n) const; // constexpr since 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,
  24                                typename std::iterator_traits<It>::difference_type n,
  25                                typename std::iterator_traits<It>::value_type x) {
  26     typedef typename std::iterator_traits<It>::value_type value_type;
  27     const std::reverse_iterator<It> r(i);
  28     value_type rr = r[n];
  29     assert(rr == x);
  30 }
  31
  32 TEST_CONSTEXPR_CXX17 bool tests() {
  33     const char* s = "1234567890";
  34     test(random_access_iterator<const char*>(s+5), 4, '1');
  35     test(random_access_iterator<const char*>(s+5), 0, '5');
  36     test(s+5, 4, '1');
  37     test(s+5, 0, '5');
  38     return true;
  39 }
  40
  41 int main(int, char**) {
  42     tests();
  43 #if TEST_STD_VER > 14
  44     static_assert(tests(), "");
  45 #endif
  46     return 0;
  47 }