libcxx/test/std/iterators/iterator.primitives/iterator.operations/next.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 // template <InputIterator Iter>
  12 //   Iter next(Iter x, Iter::difference_type n = 1); // constexpr in C++17
  13
  14 // LWG #2353 relaxed the requirement on next from ForwardIterator to InputIterator
  15
  16 #include <iterator>
  17 #include <cassert>
  18 #include <type_traits>
  19
  20 #include "test_macros.h"
  21 #include "test_iterators.h"
  22
  23 template <class It>
  24 TEST_CONSTEXPR_CXX17 void
  25 check_next_n(It it, typename std::iterator_traits<It>::difference_type n, It result)
  26 {
  27     static_assert(std::is_same<decltype(std::next(it, n)), It>::value, "");
  28     assert(std::next(it, n) == result);
  29
  30     It (*next_ptr)(It, typename std::iterator_traits<It>::difference_type) = std::next;
  31     assert(next_ptr(it, n) == result);
  32 }
  33
  34 template <class It>
  35 TEST_CONSTEXPR_CXX17 void
  36 check_next_1(It it, It result)
  37 {
  38     static_assert(std::is_same<decltype(std::next(it)), It>::value, "");
  39     assert(std::next(it) == result);
  40 }
  41
  42 TEST_CONSTEXPR_CXX17 bool tests()
  43 {
  44     const char* s = "1234567890";
  45     check_next_n(cpp17_input_iterator<const char*>(s),             10, cpp17_input_iterator<const char*>(s+10));
  46     check_next_n(forward_iterator<const char*>(s),           10, forward_iterator<const char*>(s+10));
  47     check_next_n(bidirectional_iterator<const char*>(s),     10, bidirectional_iterator<const char*>(s+10));
  48     check_next_n(bidirectional_iterator<const char*>(s+10), -10, bidirectional_iterator<const char*>(s));
  49     check_next_n(random_access_iterator<const char*>(s),     10, random_access_iterator<const char*>(s+10));
  50     check_next_n(random_access_iterator<const char*>(s+10), -10, random_access_iterator<const char*>(s));
  51     check_next_n(s, 10, s+10);
  52
  53     check_next_1(cpp17_input_iterator<const char*>(s), cpp17_input_iterator<const char*>(s+1));
  54     check_next_1(forward_iterator<const char*>(s), forward_iterator<const char*>(s+1));
  55     check_next_1(bidirectional_iterator<const char*>(s), bidirectional_iterator<const char*>(s+1));
  56     check_next_1(random_access_iterator<const char*>(s), random_access_iterator<const char*>(s+1));
  57     check_next_1(s, s+1);
  58
  59     return true;
  60 }
  61
  62 int main(int, char**)
  63 {
  64     tests();
  65 #if TEST_STD_VER >= 17
  66     static_assert(tests(), "");
  67 #endif
  68     return 0;
  69 }