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Showing content from https://en.cppreference.com/w/cpp/container/../algorithm/ranges/reverse_copy.html below:

std::ranges::reverse_copy, std::ranges::reverse_copy_result - cppreference.com

Call signature

(1) (since C++20) (2) (since C++20)

Helper types

(3) (since C++20) 1)

Copies the elements from the source range

[first, last)

to the destination range

[result, result + N)

, where

N

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

[â0â, N)

. The behavior is undefined if the source and destination ranges overlap.

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.

[edit] Parameters first, last - the iterator-sentinel pair defining the source range of elements to copy r - the source range of elements to copy result - the beginning of the destination range. [edit] Return value

{last, result + N}.

[edit] Complexity

Exactly N assignments.

[edit] 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.

[edit] 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 {};

[edit] Example

#include <algorithm>
#include <iostream>
#include <string>
 
int main()
{
    std::string x {"12345"}, y(x.size(), ' ');
    std::cout << x << " â ";
    std::ranges::reverse_copy(x.begin(), x.end(), y.begin());
    std::cout << y << " â ";
    std::ranges::reverse_copy(y, x.begin());
    std::cout << x << '\n';
}

Output:

12345 â 54321 â 12345

[edit] See also

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