text: // Range v3 library
  //
  //  Copyright Eric Niebler 2014
  //
  //  Use, modification and distribution is subject to the
  //  Boost Software License, Version 1.0. (See accompanying
  //  file LICENSE_1_0.txt or copy at
  //  http://www.boost.org/LICENSE_1_0.txt)
  //
  // Project home: https://github.com/ericniebler/range-v3
  
  #include <list>
  #include <vector>
  #include <range/v3/core.hpp>
  #include <range/v3/view/chunk.hpp>
  #include <range/v3/view/drop.hpp>
  #include <range/v3/view/iota.hpp>
  #include <range/v3/view/join.hpp>
  #include <range/v3/view/reverse.hpp>
  #include <range/v3/view/take.hpp>
  #include <range/v3/view/transform.hpp>
  #include <range/v3/utility/copy.hpp>
  #include "../simple_test.hpp"
  #include "../test_utils.hpp"
  
  int main()
  {
      using namespace ranges;
  
      int rgi[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
  
      auto rng0 = rgi | view::drop(6);
      has_type<int &>(*begin(rng0));
      models<concepts::BoundedView>(aux::copy(rng0));
      models<concepts::SizedView>(aux::copy(rng0));
      models<concepts::RandomAccessIterator>(begin(rng0));
      ::check_equal(rng0, {6, 7, 8, 9, 10});
      CHECK(size(rng0) == 5u);
  
      auto rng1 = rng0 | view::reverse;
      has_type<int &>(*begin(rng1));
      models<concepts::BoundedView>(aux::copy(rng1));
      models<concepts::SizedView>(aux::copy(rng1));
      models<concepts::RandomAccessIterator>(begin(rng1));
      ::check_equal(rng1, {10, 9, 8, 7, 6});
  
      std::vector<int> v{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
      auto rng2 = v | view::drop(6) | view::reverse;
      has_type<int &>(*begin(rng2));
      models<concepts::BoundedView>(aux::copy(rng2));
      models<concepts::SizedView>(aux::copy(rng2));
      models<concepts::RandomAccessIterator>(begin(rng2));
      ::check_equal(rng2, {10, 9, 8, 7, 6});
  
      std::list<int> l{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
      auto rng3 = l | view::drop(6);
      has_type<int &>(*begin(rng3));
      models<concepts::BoundedView>(aux::copy(rng3));
      models<concepts::SizedView>(aux::copy(rng3));
      models<concepts::BidirectionalIterator>(begin(rng3));
      models_not<concepts::RandomAccessIterator>(begin(rng3));
      ::check_equal(rng3, {6, 7, 8, 9, 10});
  
      auto rng4 = view::iota(10) | view::drop(10);
      ::models<concepts::View>(aux::copy(rng4));
      ::models_not<concepts::BoundedView>(aux::copy(rng4));
      ::models_not<concepts::SizedView>(aux::copy(rng4));
      static_assert(ranges::is_infinite<decltype(rng4)>::value, "");
      auto b = ranges::begin(rng4);
      CHECK(*b == 20);
      CHECK(*(b+1) == 21);
  
      auto rng5 = view::iota(10) | view::drop(10) | view::take(10) | view::reverse;
      ::models<concepts::BoundedView>(aux::copy(rng5));
      ::models<concepts::SizedView>(aux::copy(rng5));
      static_assert(!ranges::is_infinite<decltype(rng5)>::value, "");
      ::check_equal(rng5, {29, 28, 27, 26, 25, 24, 23, 22, 21, 20});
      CHECK(size(rng5) == 10u);
  
      {
          int some_ints[] = {0,1,2};
          auto rng = make_iterator_range(some_ints + 0, some_ints + 1);
          auto rng2 = view::drop(rng, 2);
          CHECK(begin(rng2) == some_ints + 1);
          CHECK(size(rng2) == 0u);
      }
  
      {
          // Regression test for https://github.com/ericniebler/range-v3/issues/413
          auto skips = [](std::vector<int> xs) -> std::vector<std::vector<int>> {
              return view::ints(0, (int)xs.size())
                  | view::transform([&](int n) {
                      return xs | view::chunk(n + 1)
                                | view::transform(view::drop(n))
                                | view::join;
                  });
          };
          auto skipped = skips({1,2,3,4,5,6,7,8});
          CHECK(skipped.size() == 8u);
          if(skipped.size() >= 8u)
          {
              ::check_equal(skipped[0], {1,2,3,4,5,6,7,8});
              ::check_equal(skipped[1], {2,4,6,8});
              ::check_equal(skipped[2], {3,6});
              ::check_equal(skipped[3], {4,8});
              ::check_equal(skipped[4], {5});
              ::check_equal(skipped[5], {6});
              ::check_equal(skipped[6], {7});
              ::check_equal(skipped[7], {8});
          }
      }
  
      {
          static int const some_ints[] = {0,1,2,3};
          auto rng = debug_input_view<int const>{some_ints} | view::drop(2);
          using R = decltype(rng);
          CONCEPT_ASSERT(InputView<R>());
          CONCEPT_ASSERT(!ForwardRange<R>());
          CONCEPT_ASSERT(Same<int const&, range_reference_t<R>>());
          ::check_equal(rng, {2,3});
      }
  
      return test_result();
  }
  