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/// \file
// 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.
//
//===----------------------------------------------------------------------===//
#ifndef RANGES_V3_ALGORITHM_ROTATE_HPP
#define RANGES_V3_ALGORITHM_ROTATE_HPP
#include <type_traits>
#include <utility>
#include <range/v3/range_fwd.hpp>
#include <range/v3/algorithm/move.hpp>
#include <range/v3/algorithm/move_backward.hpp>
#include <range/v3/algorithm/swap_ranges.hpp>
#include <range/v3/iterator/operations.hpp>
#include <range/v3/iterator/traits.hpp>
#include <range/v3/range/access.hpp>
#include <range/v3/range/concepts.hpp>
#include <range/v3/range/traits.hpp>
#include <range/v3/utility/move.hpp>
#include <range/v3/utility/static_const.hpp>
#include <range/v3/utility/swap.hpp>
#include <range/v3/view/subrange.hpp>
#include <range/v3/detail/prologue.hpp>
namespace ranges
{
/// \addtogroup group-algorithms
/// @{
/// \cond
namespace detail
{
template<typename I> // Forward
constexpr subrange<I> rotate_left(I first, I last)
{
iter_value_t<I> tmp = iter_move(first);
I lm1 = ranges::move(next(first), last, first).out;
*lm1 = std::move(tmp);
return {lm1, last};
}
template<typename I> // Bidirectional
constexpr subrange<I> rotate_right(I first, I last)
{
I lm1 = prev(last);
iter_value_t<I> tmp = iter_move(lm1);
I fp1 = move_backward(first, lm1, last).out;
*first = std::move(tmp);
return {fp1, last};
}
template<typename I, typename S> // Forward
constexpr subrange<I> rotate_forward(I first, I middle, S last)
{
I i = middle;
while(true)
{
ranges::iter_swap(first, i);
++first;
if(++i == last)
break;
if(first == middle)
middle = i;
}
I r = first;
if(first != middle)
{
I j = middle;
while(true)
{
ranges::iter_swap(first, j);
++first;
if(++j == last)
{
if(first == middle)
break;
j = middle;
}
else if(first == middle)
middle = j;
}
}
return {r, i};
}
template<typename D>
constexpr D gcd(D x, D y)
{
do
{
D t = x % y;
x = y;
y = t;
} while(y);
return x;
}
template<typename I> // Random
constexpr subrange<I> rotate_gcd(I first, I middle, I last)
{
auto const m1 = middle - first;
auto const m2 = last - middle;
if(m1 == m2)
{
swap_ranges(first, middle, middle);
return {middle, last};
}
auto const g = detail::gcd(m1, m2);
for(I p = first + g; p != first;)
{
iter_value_t<I> t = iter_move(--p);
I p1 = p;
I p2 = p1 + m1;
do
{
*p1 = iter_move(p2);
p1 = p2;
auto const d = last - p2;
if(m1 < d)
p2 += m1;
else
p2 = first + (m1 - d);
} while(p2 != p);
*p1 = std::move(t);
}
return {first + m2, last};
}
template<typename I, typename S>
constexpr subrange<I> rotate_(I first, I middle, S last, std::forward_iterator_tag)
{
return detail::rotate_forward(first, middle, last);
}
template<typename I>
constexpr subrange<I> rotate_(I first, I middle, I last, std::forward_iterator_tag)
{
using value_type = iter_value_t<I>;
if(detail::is_trivially_move_assignable_v<value_type>)
{
if(next(first) == middle)
return detail::rotate_left(first, last);
}
return detail::rotate_forward(first, middle, last);
}
template<typename I>
constexpr subrange<I> rotate_(I first, I middle, I last, std::bidirectional_iterator_tag)
{
using value_type = iter_value_t<I>;
if(detail::is_trivially_move_assignable_v<value_type>)
{
if(next(first) == middle)
return detail::rotate_left(first, last);
if(next(middle) == last)
return detail::rotate_right(first, last);
}
return detail::rotate_forward(first, middle, last);
}
template<typename I>
constexpr subrange<I> rotate_(I first, I middle, I last, std::random_access_iterator_tag)
{
using value_type = iter_value_t<I>;
if(detail::is_trivially_move_assignable_v<value_type>)
{
if(next(first) == middle)
return detail::rotate_left(first, last);
if(next(middle) == last)
return detail::rotate_right(first, last);
return detail::rotate_gcd(first, middle, last);
}
return detail::rotate_forward(first, middle, last);
}
} // namespace detail
/// \endcond
RANGES_FUNC_BEGIN(rotate)
/// \brief function template \c rotate
template(typename I, typename S)(
requires permutable<I> AND sentinel_for<S, I>)
constexpr subrange<I> RANGES_FUNC(rotate)(I first, I middle, S last) //
{
if(first == middle)
{
first = ranges::next(std::move(first), last);
return {first, first};
}
if(middle == last)
{
return {first, middle};
}
return detail::rotate_(first, middle, last, iterator_tag_of<I>{});
}
/// \overload
template(typename Rng, typename I = iterator_t<Rng>)(
requires range<Rng> AND permutable<I>)
constexpr borrowed_subrange_t<Rng> RANGES_FUNC(rotate)(Rng && rng, I middle) //
{
return (*this)(begin(rng), std::move(middle), end(rng));
}
RANGES_FUNC_END(rotate)
namespace cpp20
{
using ranges::rotate;
}
/// @}
} // namespace ranges
#include <range/v3/detail/epilogue.hpp>
#endif
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