std::move_backward(3)

NAME
std::move_backward - std::move_backward

Synopsis
   Defined in header <algorithm>
   template< class BidirIt1, class BidirIt2 > (since C++11)
   BidirIt2 move_backward( BidirIt1 first, BidirIt1 last, BidirIt2 (until C++20)
   d_last );
   template< class BidirIt1, class BidirIt2 >
   constexpr BidirIt2 move_backward( BidirIt1 first, BidirIt1 last, (since C++20)
   BidirIt2 d_last );
   Moves the elements from the range [first, last), to another range ending at d_last.
   The elements are moved in reverse order (the last element is moved first), but their
   relative order is preserved.
   The behavior is undefined if d_last is within (first, last]. std::move must be used
   instead of std::move_backward in that case.

Parameters
   first, last - the range of the elements to move
   d_last - end of the destination range

Type requirements
   -
   BidirIt1, BidirIt2 must meet the requirements of LegacyBidirectionalIterator.

Return value
   Iterator in the destination range, pointing at the last element moved.

Complexity
   Exactly last - first move assignments.

Possible implementation
   template< class BidirIt1, class BidirIt2 >
   BidirIt2 move_backward(BidirIt1 first, BidirIt1 last,
                        BidirIt2 d_last)
   {
       while (first != last) {
           *(--d_last) = std::move(*(--last));
       }
       return d_last;
   }

Notes
   When moving overlapping ranges, std::move is appropriate when moving to the left
   (beginning of the destination range is outside the source range) while
   std::move_backward is appropriate when moving to the right (end of the destination
   range is outside the source range).

Example
// Run this code
 #include <algorithm>
 #include <iostream>
 #include <iterator>
 #include <string>
 #include <string_view>
 #include <vector>
 using container = std::vector<std::string>;
 void print(std::string_view comment, const container& src, const container& dst = {})
 {
     auto prn = [](std::string_view name, const container& cont) {
         std::cout << name;
         for (const auto &s: cont) { std::cout << (s.empty() ? "∙" : s.data()) << ' '; }
         std::cout << '\n';
     };
     std::cout << comment << '\n';
     prn("src: ", src);
     if (dst.empty()) return;
     prn("dst: ", dst);
 }
 int main()
 {
     container src{"foo", "bar", "baz"};
     container dst{"qux", "quux", "quuz", "corge"};
     print("Non-overlapping case; before move_backward:", src, dst);
     std::move_backward(src.begin(), src.end(), dst.end());
     print("After:", src, dst);
     src = {"snap", "crackle", "pop", "lock", "drop"};
     print("Overlapping case; before move_backward:", src);
     std::move_backward(src.begin(), std::next(src.begin(), 3), src.end());
     print("After:", src);
 }

Output:
 Non-overlapping case; before move_backward:
 src: foo bar baz
 dst: qux quux quuz corge
 After:
 src: ∙ ∙ ∙
 dst: qux foo bar baz
 Overlapping case; before move_backward:
 src: snap crackle pop lock drop
 After:
 src: ∙ ∙ snap crackle pop

See also
   move moves a range of elements to a new location
   (C++11) (function template)
   ranges::move_backward moves a range of elements to a new location in backwards order
   (C++20) (niebloid)