llvm/libcxx/test/std/iterators/predef.iterators/move.iterators/move.iter.ops/move.iter.op.index/difference_type.pass.cpp

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

// <iterator>

// move_iterator

// constexpr reference operator[](difference_type n) const; // Return type unspecified until C++20

#include <iterator>
#include <cassert>
#include <memory>

#include "test_macros.h"
#include "test_iterators.h"

template <class It>
void
test(It i, typename std::iterator_traits<It>::difference_type n,
     typename std::iterator_traits<It>::value_type x)
{
    typedef typename std::iterator_traits<It>::value_type value_type;
    const std::move_iterator<It> r(i);
    value_type rr = r[n];
    assert(rr == x);
}

struct do_nothing
{
    void operator()(void*) const {}
};

int main(int, char**)
{
    {
        char s[] = "1234567890";
        test(random_access_iterator<char*>(s+5), 4, '0');
        test(s+5, 4, '0');
    }
#if TEST_STD_VER >= 11
    {
        int i[5];
        typedef std::unique_ptr<int, do_nothing> Ptr;
        Ptr p[5];
        for (unsigned j = 0; j < 5; ++j)
            p[j].reset(i+j);
        test(p, 3, Ptr(i+3));
    }
#endif
#if TEST_STD_VER > 14
    {
    constexpr const char *p = "123456789";
    typedef std::move_iterator<const char *> MI;
    constexpr MI it1 = std::make_move_iterator(p);
    static_assert(it1[0] == '1', "");
    static_assert(it1[5] == '6', "");
    }
#endif

#if TEST_STD_VER > 17
  // Ensure the `iter_move` customization point is being used.
  {
    int a[] = {0, 1, 2};

    int iter_moves = 0;
    adl::Iterator i = adl::Iterator::TrackMoves(a, iter_moves);
    std::move_iterator<adl::Iterator> mi(i);

    auto x = mi[0];
    assert(x == 0);
    assert(iter_moves == 1);
  }
#endif

  return 0;
}