std::move_backward - cppreference.com (original) (raw)

| | | | | ---------------------------------------------------------------------------------------------------------------------- | | ------------------------------------- | | template< class BidirIt1, class BidirIt2 >BidirIt2 move_backward( BidirIt1 first, BidirIt1 last, BidirIt2 d_last ); | | (since C++11) (constexpr since C++20) |

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.

If d_last is within (first, last], the behavior is undefined. In this case, std::move may be used instead.

Contents

• 1 Parameters
• 2 Return value
• 3 Complexity
• 4 Possible implementation
• 5 Notes
• 6 Example
• 7 See also

[edit] Parameters

[edit] Return value

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

[edit] Complexity

Exactly std::distance(first, last) move assignments.

[edit] 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; }

[edit] 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).

[edit] Example

#include #include #include #include #include #include   using container = std::vector<std::string>;   void print(std::string_view comment, const container& src, const container& dst = {}) { auto prn = 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

[edit] See also

| | moves a range of elements to a new location (function template) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | moves a range of elements to a new location in backwards order(algorithm function object)[edit] |