Defined in header <algorithm> | ||
---|---|---|
template< class InputIt, class Size, class OutputIt > OutputIt copy_n( InputIt first, Size count, OutputIt result ); | (since C++11) |
Copies exactly count
values from the range beginning at first
to the range beginning at result
, if count>0
. Does nothing otherwise.
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 . |
Return value
Iterator in the destination range, pointing past the last element copied if count>0
or result
otherwise.
Complexity
Exactly count
assignments, if count>0
.
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; } |
Example
#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
See also
(C++11) | copies a range of elements to a new location (function template) |
std::experimental::parallel::copy_n
(parallelism TS) | parallelized version of std::copy_n (function template) |
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