 

Category: algorithms   Component type: function 
Prototype
template <class InputIterator, class Size, class OutputIterator>
OutputIterator copy_n(InputIterator first, Size count,
OutputIterator result);
Description
Copy_n
copies elements from the range [first, first + n)
to the range [result, result + n)
. That is, it performs the assignments *result = *first
, *(result + 1) = *(first + 1)
, and so on. Generally, for every integer i
from 0
up to (but not including) n
, copy_n
performs the assignment *(result + i) = *(first + i)
. Assignments are performed in forward order, i.e. in order of increasing n
. [1]
The return value is result + n
.
Definition
Defined in the standard header algorithm, and in the nonstandard backwardcompatibility header algo.h. This function is an SGI extension; it is not part of the C++ standard.
Requirements on types

InputIterator is a model of InputIterator.

OutputIterator is a model of OutputIterator.

Size
is an integral type.

InputIterator's value type is convertible to a type in OutputIterator's set of value types.
Preconditions

n >= 0
.

[first, first + n)
is a valid range.

result
is not an iterator within the range [first, first + n)
.

[result, result + n)
is a valid range.
Complexity
Linear. Exactly n
assignments are performed.
Example
Vector<int> V(5);
iota(V.begin(), V.end(), 1);
List<int> L(V.size());
copy_n(V.begin(), V.size(), L.begin());
assert(equal(V.begin(), V.end(), L.begin()));
Notes
[1] Copy_n
is almost, but not quite, redundant. If first
is an InputIterator, as opposed to a ForwardIterator, then the copy_n
operation can't be expressed in terms of copy
.
See also
copy
, copy_backward