std::ranges::rotate_copy, std::ranges::rotate_copy_result
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Defined in header
<algorithm>
Call signature
template< std::forward_iterator I, std::sentinel_for <I> S,
(1)
(since C++20)
std::weakly_incrementable O >
requires std::indirectly_copyable <I, O>
constexpr rotate_copy_result<I, O>
template< ranges::forward_range R, std::weakly_incrementable O >
(2)
(since C++20)
requires std::indirectly_copyable <ranges::iterator_t <R>, O>
constexpr rotate_copy_result<ranges::borrowed_iterator_t <R>, O>
Helper types
template< class I, class O >
using rotate_copy_result = in_out_result<I, O>;
(3)
(since C++20)
using rotate_copy_result = in_out_result<I, O>;
Copies the left rotation of [first, last) to result.
1) Copies the elements from the source range
[first, last), such that in the destination range, the elements in [first, middle) are placed after the elements in [middle, last) while the orders of the elements in both ranges are preserved. 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 algorithm function objects (informally known as 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.
Contents
[edit] Parameters
first, last
-
the iterator-sentinel pair defining 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
[edit] Return value
{last, result + N}, where N = ranges::distance (first, last).
[edit] Complexity
Linear: exactly N assignments.
[edit] 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 .
[edit] 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 {};
[edit] 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