Std::move_backward (3) Linux Manual Page

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

std::move_backward (3) Linux Manual Page