std::ranges::uninitialized_copy_n, std::ranges::uninitialized_copy_n_result

Since C++20

Header: <memory>

Let (\scriptsize N)N be ranges::min(count, ranges::distance(ofirst, olast)).

# Declarations

Call signature

template< std::input_iterator I,
no-throw-input-iterator O, no-throw-sentinel-for<O> S >
requires std::constructible_from<std::iter_value_t<O>,
std::iter_reference_t<I>>
uninitialized_copy_n_result<I, O>
uninitialized_copy_n( I ifirst, std::iter_difference_t<I> count,
O ofirst, S olast );

(since C++20) (constexpr since C++26)

Helper types

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

(since C++20)

# Parameters

# Return value

As described above.

# Notes

An implementation may improve the efficiency of the ranges::uninitialized_copy_n, by using e.g. ranges::copy_n, if the value type of the output range is TrivialType.

# Example

#include <iomanip>
#include <iostream>
#include <memory>
#include <string>
 
int main()
{
    const char* stars[]{"Procyon", "Spica", "Pollux", "Deneb", "Polaris"};
 
    constexpr int n{4};
    alignas(alignof(std::string)) char out[n * sizeof(std::string)];
 
    try
    {
        auto first{reinterpret_cast<std::string*>(out)};
        auto last{first + n};
        auto ret{std::ranges::uninitialized_copy_n(std::begin(stars), n, first, last)};
 
        std::cout << '{';
        for (auto it{first}; it != ret.out; ++it)
            std::cout << (it == first ? "" : ", ") << std::quoted(*it);
        std::cout << "};\n";
 
        std::ranges::destroy(first, last);
    }
    catch (...)
    {
        std::cout << "uninitialized_copy_n exception\n";
    }
}

# See also