Defined in header <algorithm> | ||
---|---|---|
template< class BidirIt1, class BidirIt2 > BidirIt2 copy_backward( BidirIt1 first, BidirIt1 last, BidirIt2 d_last ); |
Copies the elements from the range, defined by [first, last)
, to another range ending at d_last
. The elements are copied in reverse order (the last element is copied first), but their relative order is preserved.
The behavior is undefined if d_last
is within (first, last]
. std::copy
must be used instead of std::copy_backward
in that case.
Parameters
first, last | - | the range of the elements to copy |
d_last | - | end of the destination range.. |
Type requirements | ||
- BidirIt must meet the requirements of BidirectionalIterator . |
Return value
iterator to the last element copied.
Complexity
Exactly last - first
assignments.
Notes
When copying overlapping ranges, std::copy
is appropriate when copying to the left (beginning of the destination range is outside the source range) while std::copy_backward
is appropriate when copying to the right (end of the destination range is outside the source range).
Possible implementation
template< class BidirIt1, class BidirIt2 > BidirIt2 copy_backward(BidirIt1 first, BidirIt1 last, BidirIt2 d_last) { while (first != last) { *(--d_last) = *(--last); } return d_last; } |
Example
#include <algorithm> #include <iostream> #include <vector> int main() { std::vector<int> from_vector; for (int i = 0; i < 10; i++) { from_vector.push_back(i); } std::vector<int> to_vector(15); std::copy_backward(from_vector.begin(), from_vector.end(), to_vector.end()); std::cout << "to_vector contains: "; for (unsigned int i = 0; i < to_vector.size(); i++) { std::cout << to_vector[i] << " "; } }
Output:
to_vector contains: 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9
See also
(C++11) | copies a range of elements to a new location (function template) |
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