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# copy_n

Copies a specified number of elements View version details

### Key Facts

Gyroscopic Couple: The rate of change of angular momentum ( ) = (In the limit).
• = Moment of Inertia.
• = Angular velocity
• = Angular velocity of precession.

Blaise Pascal (1623-1662) was a French mathematician, physicist, inventor, writer and Catholic philosopher.

Leonhard Euler (1707-1783) was a pioneering Swiss mathematician and physicist.

## Definition

The copy_n() algorithm is defined in the standard header <algorithm> and in the nonstandard backward-compatibility header <algo.h>.

## Interface

#include <algorithm>
template < class InputIterator, class Size, class OutputIterator >
OutputIterator copy_n(
InputIterator  first,
Size count,
OutputIterator result
);

Parameters:
Parameter Description
first An input iterator that indicates where to copy elements from
count A signed or unsigned integer type specifying the number of elements to copy
result An output iterator that indicates where to copy elements to

## Description

Copy_n copies elements from the range [first, first + n) to the range [result, result + n).

## Return Value

Returns an output iterator where elements have been copied to. It is the same as the returned value of the third parameter, result.

## Complexity

The complexity is linear, n assignments are performed.

### References

Example:
##### Example - copy_n algorithm
Problem
This example of program illustrates the functionality of copy_n() algorithm.
Workings
#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';

return 0;
}
Solution
Output:

1234
References