##### cppreference.com

##### Search

Create account

##### Namespaces

- Page
- Discussion

##### Variants

##### Views

- View
- Edit
- History

##### Actions

# std::copy_n

From cppreference.com
< cpp‎ | algorithm

Defined in header `<algorithm>` |  |
template< class InputIt, class Size, class OutputIt > OutputIt copy_n( InputIt first, Size count, OutputIt result ); |  |

Copies exactly `count` values from the range beginning at `first` to the range beginning at `result`, if `count>0`. Does nothing otherwise.

### [edit] Parameters

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
Type requirements
- `InputIt` must meet the requirements of `InputIterator`.
- `OutputIt` must meet the requirements of `OutputIterator`.

### [edit] Return value

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

### [edit] Complexity

Exactly `count` assignments, if `count>0`.

### [edit] Possible implementation

    template< class InputIt, class Size, class OutputIt>
    OutputIt copy_n(InputIt first, Size count, OutputIt result)
    {
        if (count > 0) {
            *result++ = *first;
            for (Size i = 1; i < count; ++i) {
                *result++ = *++first;
            }
        }
        return result;
    }

### [edit] Example

Run this code

    #include <iostream>
    #include <string>
    #include <algorithm>
    #include <iterator>

    int main()
    {
        std::string in = "1234567890";
        std::string out;

        std::copy_n(in.begin(), 4, std::back_inserter(out));
        std::cout << out << '\n';
    }

Output:

    1234

### [edit] See also

copy copy_if (C++11) | copies a range of elements to a new location (function template) [edit]

Retrieved from "http://en.cppreference.com/mwiki/index.php?title=cpp/algorithm/copy_n&oldid=66463"