NAME¶

std::ranges::rotate_copy,std::ranges::rotate_copy_result - std::ranges::rotate_copy,std::ranges::rotate_copy_result

Synopsis¶

Defined in header <algorithm>
Call signature
template< std::forward_iterator I, std::sentinel_for<I> S,

std::weakly_incrementable O >
requires std::indirectly_copyable<I, O> (1) (since C++20)
constexpr rotate_copy_result<I, O>

rotate_copy( I first, I middle, S last, O result );
template< ranges::forward_range R, std::weakly_incrementable O >

requires std::indirectly_copyable<ranges::iterator_t<R>, O> (2) (since C++20)
constexpr rotate_copy_result<ranges::borrowed_iterator_t<R>, O>

rotate_copy( R&& r, ranges::iterator_t<R> middle, O result );

Helper types¶

template< class I, class O > (3) (since C++20)
using rotate_copy_result = in_out_result<I, O>;

1) Copies the elements from the source range [first, last), to the destination range
beginning at result in such a way, that the element *middle becomes the first
element of the destination range and *(middle - 1) becomes the last element. The
result is that the destination range contains a left rotated copy of the source
range.
The behavior is undefined if either [first, middle) or [middle, last) is not a valid
range, or the source and destination ranges overlap.
2) Same as (1), but uses r as the source range, as if using ranges::begin(r) as
first and ranges::end(r) as last.

The function-like entities described on this page are niebloids, that is:

* Explicit template argument lists cannot be specified when calling any of them.
* None of them are visible to argument-dependent lookup.
* When any of them are found by normal unqualified lookup as the name to the left
of the function-call operator, argument-dependent lookup is inhibited.

In practice, they may be implemented as function objects, or with special compiler
extensions.

Parameters¶

first, last - the source range of elements to copy from
r - the source range of elements to copy from
middle - the iterator to the element that should appear at the beginning of the
destination range
result - beginning of the destination range

Return value¶

{last, result + N}, where N = ranges::distance(first, last).

Complexity¶

Linear: exactly N assignments.

Notes¶

If the value type is TriviallyCopyable and the iterator types satisfy
contiguous_iterator, implementations of ranges::rotate_copy usually avoid multiple
assignments by using a "bulk copy" function such as std::memmove.

Possible implementation¶

See also the implementations in libstdc++ and MSVC STL.

struct rotate_copy_fn {
template<std::forward_iterator I, std::sentinel_for<I> S, std::weakly_incrementable O>
requires std::indirectly_copyable<I, O>
constexpr ranges::rotate_copy_result<I, O>
operator()(I first, I middle, S last, O result) const
{
auto c1 {ranges::copy(middle, std::move(last), std::move(result))};
auto c2 {ranges::copy(std::move(first), std::move(middle), std::move(c1.out))};
return {std::move(c1.in), std::move(c2.out)};
}

template<ranges::forward_range R, std::weakly_incrementable O>
requires std::indirectly_copyable<ranges::iterator_t<R>, O>
constexpr ranges::rotate_copy_result<ranges::borrowed_iterator_t<R>, O>
operator()(R&& r, ranges::iterator_t<R> middle, O result) const
{
return (*this)(ranges::begin(r), std::move(middle),
ranges::end(r), std::move(result));
} };

inline constexpr rotate_copy_fn rotate_copy {};

Example¶

// Run this code

#include <algorithm>
#include <iostream>
#include <iterator>
#include <vector>

int main()
{
std::vector<int> src {1, 2, 3, 4, 5};
std::vector<int> dest(src.size());
auto pivot = std::ranges::find(src, 3);

std::ranges::rotate_copy(src, pivot, dest.begin());
for (int i : dest)
std::cout << i << ' ';
std::cout << '\n';

// copy the rotation result directly to the std::cout
pivot = std::ranges::find(dest, 1);
std::ranges::rotate_copy(dest, pivot, std::ostream_iterator<int>(std::cout, " "));
std::cout << '\n';
}

Output:¶

3 4 5 1 2
1 2 3 4 5

See also¶

ranges::rotate rotates the order of elements in a range
(C++20) (niebloid)
ranges::copy
ranges::copy_if copies a range of elements to a new location
(C++20) (niebloid)
(C++20)
rotate_copy copies and rotate a range of elements
(function template)