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| 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 backward-compatibility header algo.h. This function is an SGI extension; it is not part of the C++ standard.
Requirements on types
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InputIterator is a model of InputIterator.
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OutputIterator is a model of OutputIterator.
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Size is an integral type.
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InputIterator's value type is convertible to a type in OutputIterator's set of value types.
Preconditions
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n >= 0.
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[first, first + n) is a valid range.
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result is not an iterator within the range [first, first + n).
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[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
