std::move_backward (3) - Linux Manuals

std::move_backward: std::move_backward

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 d_last ); (until C++20)
template< class BidirIt1, class BidirIt2 > (since C++20)
constexpr BidirIt2 move_backward( BidirIt1 first, BidirIt1 last, 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 <vector>
  #include <string>
  #include <iostream>

  int main()
  {
      std::vector<std::string> src{"foo", "bar", "baz"};
      std::vector<std::string> dest(src.size());

      std::cout << "src: ";
      for (const auto &s : src)
      {
          std::cout << s << ' ';
      }
      std::cout << "\ndest: ";
      for (const auto &s : dest)
      {
          std::cout << s << ' ';
      }
      std::cout << '\n';

      std::move_backward(src.begin(), src.end(), dest.end());

      std::cout << "src: ";
      for (const auto &s : src)
      {
          std::cout << s << ' ';
      }
      std::cout << "\ndest: ";
      for (const auto &s : dest)
      {
          std::cout << s << ' ';
      }
      std::cout << '\n';
  }

Output:

  src: foo bar baz
  dest:
  src:
  dest: foo bar baz