text: // Range v3 library
  //
  //  Copyright Eric Niebler 2014-present
  //
  //  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
  
  //===----------------------------------------------------------------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is dual licensed under the MIT and the University of Illinois Open
  // Source Licenses. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  
  #include <vector>
  #include <range/v3/core.hpp>
  #include <range/v3/algorithm/generate.hpp>
  #include <range/v3/iterator/insert_iterators.hpp>
  #include <range/v3/view/counted.hpp>
  #include "../simple_test.hpp"
  #include "../test_utils.hpp"
  #include "../test_iterators.hpp"
  
  struct gen_test
  {
      int i_;
      constexpr gen_test()
        : i_{}
      {}
      constexpr gen_test(int i)
        : i_(i)
      {}
      constexpr int operator()()
      {
          return i_++;
      }
  };
  
  template<class Iter, class Sent = Iter>
  void
  test()
  {
      const unsigned n = 4;
      int ia[n] = {0};
      ranges::generate_result<Iter, gen_test> res = ranges::generate(Iter(ia), Sent(ia + n), gen_test(1));
      CHECK(ia[0] == 1);
      CHECK(ia[1] == 2);
      CHECK(ia[2] == 3);
      CHECK(ia[3] == 4);
      CHECK(res.out == Iter(ia + n));
      CHECK(res.fun.i_ == 5);
  
      auto rng = ::MakeTestRange(Iter(ia), Sent(ia + n));
      res = ranges::generate(rng, res.fun);
      CHECK(ia[0] == 5);
      CHECK(ia[1] == 6);
      CHECK(ia[2] == 7);
      CHECK(ia[3] == 8);
      CHECK(res.out == Iter(ia + n));
      CHECK(res.fun.i_ == 9);
  
      auto res2 = ranges::generate(std::move(rng), res.fun);
      CHECK(ia[0] == 9);
      CHECK(ia[1] == 10);
      CHECK(ia[2] == 11);
      CHECK(ia[3] == 12);
      CHECK(::is_dangling(res2.out));
      CHECK(res2.fun.i_ == 13);
  }
  
  void test2()
  {
      // Test ranges::generate with a genuine output range
      std::vector<int> v;
      auto rng = ranges::views::counted(ranges::back_inserter(v), 5);
      ranges::generate(rng, gen_test(1));
      CHECK(v.size() == 5u);
      CHECK(v[0] == 1);
      CHECK(v[1] == 2);
      CHECK(v[2] == 3);
      CHECK(v[3] == 4);
      CHECK(v[4] == 5);
  }
  
  template<class Iter, class Sent = Iter>
  constexpr bool test_constexpr()
  {
      const unsigned n = 4;
      int ia[n] = {0};
      const auto res = ranges::generate(Iter(ia), Sent(ia + n), gen_test(1));
      STATIC_CHECK_RETURN(ia[0] == 1);
      STATIC_CHECK_RETURN(ia[1] == 2);
      STATIC_CHECK_RETURN(ia[2] == 3);
      STATIC_CHECK_RETURN(ia[3] == 4);
      STATIC_CHECK_RETURN(res.out == Iter(ia + n));
      STATIC_CHECK_RETURN(res.fun.i_ == 5);
  
      auto rng = ranges::make_subrange(Iter(ia), Sent(ia + n));
      const auto res2 = ranges::generate(rng, res.fun);
      STATIC_CHECK_RETURN(ia[0] == 5);
      STATIC_CHECK_RETURN(ia[1] == 6);
      STATIC_CHECK_RETURN(ia[2] == 7);
      STATIC_CHECK_RETURN(ia[3] == 8);
      STATIC_CHECK_RETURN(res2.out == Iter(ia + n));
      STATIC_CHECK_RETURN(res2.fun.i_ == 9);
  
      const auto res3 = ranges::generate(std::move(rng), res2.fun);
      STATIC_CHECK_RETURN(ia[0] == 9);
      STATIC_CHECK_RETURN(ia[1] == 10);
      STATIC_CHECK_RETURN(ia[2] == 11);
      STATIC_CHECK_RETURN(ia[3] == 12);
      STATIC_CHECK_RETURN(res3.out == Iter(ia + n));
      STATIC_CHECK_RETURN(res3.fun.i_ == 13);
      
      return true;
  }
  
  int main()
  {
      test<ForwardIterator<int*> >();
      test<BidirectionalIterator<int*> >();
      test<RandomAccessIterator<int*> >();
      test<int*>();
  
      test<ForwardIterator<int*>, Sentinel<int*> >();
      test<BidirectionalIterator<int*>, Sentinel<int*> >();
      test<RandomAccessIterator<int*>, Sentinel<int*> >();
  
      test2();
  
      STATIC_CHECK(test_constexpr<ForwardIterator<int *>>());
      STATIC_CHECK(test_constexpr<BidirectionalIterator<int *>>());
      STATIC_CHECK(test_constexpr<RandomAccessIterator<int *>>());
      STATIC_CHECK(test_constexpr<int *>());
      STATIC_CHECK(test_constexpr<ForwardIterator<int *>, Sentinel<int *>>());
      STATIC_CHECK(test_constexpr<BidirectionalIterator<int *>, Sentinel<int *>>());
      STATIC_CHECK(test_constexpr<RandomAccessIterator<int *>, Sentinel<int *>>());
      
      return ::test_result();
  }
  