std::copy_n (3) - Linux Manuals
Defined in header <algorithm>
template< class InputIt, class Size, class OutputIt > (since C++11)
OutputIt copy_n( InputIt first, Size count, OutputIt result ); (until C++20)
template< class InputIt, class Size, class OutputIt > (1) (since C++20)
constexpr OutputIt copy_n( InputIt first, Size count, OutputIt result );
template< class ExecutionPolicy, class ForwardIt1, class Size, class ForwardIt2 > (2) (since C++17)
ForwardIt2 copy_n( ExecutionPolicy&& policy, ForwardIt1 first, Size count, ForwardIt2 result );
1) Copies exactly count values from the range beginning at first to the range beginning at result. Formally, for each non-negative integer i < n, performs *(result + i) = *(first + i). Overlap of ranges is not permitted.
2) Same as (1), but executed according to policy. This overload only participates in overload resolution if std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true
first - the beginning of the range of elements to copy from
count - number of the elements to copy
result - the beginning of the destination range
policy - the execution policy to use. See execution_policy for details.
InputIt must meet the requirements of LegacyInputIterator.
OutputIt must meet the requirements of LegacyOutputIterator.
ForwardIt1, ForwardIt2 must meet the requirements of LegacyForwardIterator.
Iterator in the destination range, pointing past the last element copied if count>0 or result otherwise.
Exactly count assignments, if count>0.
The overload with a template parameter named ExecutionPolicy reports errors as follows:
* If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard_policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
* If the algorithm fails to allocate memory, std::bad_alloc is thrown.
// Run this code
copy_if copies a range of elements to a new location