std::ranges::reverse_copy, std::ranges::reverse_copy_result

Since C++20

Header: <algorithm>

  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.

# Declarations

Call signature

template< std::bidirectional_iterator I, std::sentinel_for<I> S,
std::weakly_incrementable O >
requires std::indirectly_copyable<I, O>
constexpr reverse_copy_result<I, O>
reverse_copy( I first, S last, O result );

(since C++20)

template< ranges::bidirectional_range R, std::weakly_incrementable O >
requires std::indirectly_copyable<ranges::iterator_t<R>, O>
constexpr reverse_copy_result<ranges::borrowed_iterator_t<R>, O>
reverse_copy( R&& r, O result );

(since C++20)

Helper types

template< class I, class O >
using reverse_copy_result = ranges::in_out_result<I, O>;

(since C++20)

# Parameters

# Return value

{last, result + N}.

# 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.

# Example

#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';
}

# See also