Copies the elements from the range[first, last) to another range ending atd_last. The elements are copied in reverse order (the last element is copied first), but their relative order is preserved.

The behavior is undefined ifd_last is within(first, last].std::copy must be used instead ofstd::copy_backward in that case.

[edit]Parameters

[edit]Return value

Iterator to the last element copied.

[edit]Complexity

Exactlystd::distance(first, last) assignments.

[edit]Notes

When copying overlapping ranges,std::copy is appropriate when copying to the left (beginning of the destination range is outside the source range) whilestd::copy_backward is appropriate when copying to the right (end of the destination range is outside the source range).

[edit]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;}

[edit]Example

#include <algorithm>#include <iostream>#include <numeric>#include <vector> int main(){std::vector<int> source(4);std::iota(source.begin(), source.end(),1);// fills with 1, 2, 3, 4 std::vector<int> destination(6);     std::copy_backward(source.begin(), source.end(), destination.end()); std::cout<<"destination contains: ";for(auto i: destination)std::cout<< i<<' ';std::cout<<'\n';}

destination contains: 0 0 1 2 3 4

[edit]Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit]See also

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