Moving elements from std::vector to another one

Question

How can I move some elements from first vector to second, and the elements will remove from the first?
if I am using std::move, the elements not removed from first vector.
this is the code I wrote:

   move(xSpaces1.begin() + 7, xSpaces1.end(), back_inserter(xSpaces2)); 

Answer 1

Resurrecting an old thread, but I am surprised that nobody mentioned std::make_move_iterator combined with insert. It has the important performance benefit of preallocating space in the target vector:

v2.insert(v2.end(), std::make_move_iterator(v1.begin() + 7),                      std::make_move_iterator(v1.end())); 

As others have pointed out, first vector v1 is now in indeterminate state, so use erase to clear the mess:

v1.erase(v1.begin() + 7, v1.end()); 

Answer 2

std::move and std::copy operate on elements, not containers. You have to mutate the container separately. For example, to move the first 17 elements of v1 into a new vector v2:

std::vector<Foo> v1, v2;  // populate v1 with at least 17 elements...  auto it = std::next(v1.begin(), 17);  std::move(v1.begin(), it, std::back_inserter(v2));  // ##  v1.erase(v1.begin(), it); 

After line ##, the first 17 elements of v1 are still there, but they've been "moved-from", so they're in an indeterminate state.