std::ranges::reverse_copy, std::ranges::reverse_copy_result
From cppreference.com
| Defined in header <algorithm>
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| Call signature |
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| template< std::bidirectional_iterator I, std::sentinel_for<I> S, std::weakly_incrementable O > |
(1) | (since C++20) |
| template< ranges::bidirectional_range R, std::weakly_incrementable O > requires std::indirectly_copyable<ranges::iterator_t<R>, O> |
(2) | (since C++20) |
| Helper types |
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| template< class I, class O > using reverse_copy_result = ranges::in_out_result<I, O>; |
(3) | (since C++20) |
1) Copies the elements from the source range
[first, last) to the destination range [result, result + N), where N is ranges::distance(first, last), in such a way that the elements in the new range are in reverse order. Behaves as if by executing the assignment *(result + N - 1 - i) = *(first + i) once for each integer i in [0, N). The behavior is undefined if 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 range of elements to copy |
| r | - | the range of elements to copy |
| result | - | the beginning of the destination range. |
Return value
{last, result + N}.
Complexity
Exactly N assignments.
Notes
Implementations (e.g. MSVC STL) may enable vectorization when the both iterator types model contiguous_iterator and have the same value type, and the value type is TriviallyCopyable.
Possible implementation
See also the implementations in MSVC STL and libstdc++.
struct reverse_copy_fn { template<std::bidirectional_iterator I, std::sentinel_for<I> S, std::weakly_incrementable O> requires std::indirectly_copyable<I, O> constexpr ranges::reverse_copy_result<I, O> operator()(I first, S last, O result) const { auto ret = ranges::next(first, last); for (; last != first; *result = *--last, ++result); return {std::move(ret), std::move(result)}; } template<ranges::bidirectional_range R, std::weakly_incrementable O> requires std::indirectly_copyable<ranges::iterator_t<R>, O> constexpr ranges::reverse_copy_result<ranges::borrowed_iterator_t<R>, O> operator()(R&& r, O result) const { return (*this)(ranges::begin(r), ranges::end(r), std::move(result)); } }; inline constexpr reverse_copy_fn reverse_copy {}; |
Example
Run this code
#include <algorithm> #include <iostream> #include <string> int main() { std::string x {"12345"}, y(x.size(), ' '); std::cout << x << " → "; std::ranges::reverse_copy(x.begin(), x.end(), y.begin()); std::cout << y << " → "; std::ranges::reverse_copy(y, x.begin()); std::cout << x << '\n'; }
Output:
12345 → 54321 → 12345
See also
| (C++20) |
reverses the order of elements in a range (niebloid) |
| creates a copy of a range that is reversed (function template) |