std::ranges::rotate_copy, std::ranges::rotate_copy_result
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>
constexpr rotate_copy_result<I, O>
rotate_copy( I first, I middle, S last, O result ); |
(1) | (since C++20) |
template< ranges::forward_range R, std::weakly_incrementable O >
requires std::indirectly_copyable<ranges::iterator_t<R>, O>
constexpr rotate_copy_result<ranges::borrowed_iterator_t<R>, O>
rotate_copy( R&& r, ranges::iterator_t<R> middle, O result ); |
(2) | (since C++20) |
| Helper types | ||
template< class I, class O > using rotate_copy_result = in_out_result<I, O>; |
(3) | (since C++20) |
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 may not be specified when calling any of them.
- None of them is visible to argument-dependent lookup.
- When one of them is found by normal unqualified lookup for the name to the left of the function-call operator, it inhibits argument-dependent lookup.
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
#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
|
(C++20)
|
rotates the order of elements in a range (niebloid) |
|
(C++20)(C++20)
|
copies a range of elements to a new location (niebloid) |
| copies and rotate a range of elements (function template) |
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