std::copy_n - cppreference.com (original) (raw)

1. Copies exactly count values from the range beginning at first to the range beginning at result. Formally, for each integer i in [​0​, count), performs *(result + i) = *(first + i).

Overlap of ranges is formally permitted, but leads to unpredictable ordering of the results.

1. Same as (1), but executed according to policy.

This overload participates in overload resolution only if all following conditions are satisfied:

Contents

• 1 Parameters
• 2 Return value
• 3 Complexity
• 4 Exceptions
• 5 Possible implementation
• 6 Example
• 7 See also

[edit] Parameters

[edit] Return value

Iterator in the destination range, pointing past the last element copied if count > 0 or result otherwise.

[edit] Complexity

Zero assignments if count < 0; count assignments otherwise.

[edit] Exceptions

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.

[edit] Possible implementation

template<class InputIt, class Size, class OutputIt> constexpr //< since C++20 OutputIt copy_n(InputIt first, Size count, OutputIt result) { if (count > 0) { *result = *first; ++result; for (Size i = 1; i != count; ++i, (void)++result) *result = *++first; }   return result; }

[edit] Example

[edit] See also

| | copies a range of elements to a new location (function template) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | copies a number of elements to a new location(algorithm function object)[edit] |