template< class BidirIt1, class BidirIt2 >
BidirIt2 copy_backward( BidirIt1 first, BidirIt1 last, BidirIt2 d_last );
Copies the elements from the range [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.
BidirIt must meet the requirements of LegacyBidirectionalIterator. [edit] Return value
Iterator to the last element copied.
[edit] ComplexityExactly std::distance(first, last) assignments.
[edit] NotesWhen 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).
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';
}
Output:
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.
DR Applied to Behavior as published Correct behavior LWG 1206 C++98 1. the behavior was well-defined if d_last == lastRetroSearch is an open source project built by @garambo | Open a GitHub Issue
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