9.22: Iterator mid is invalidated any time an insertion before it occurs

[xjay73]

The program also has an error in that the location of mid must be handled some other way, as the iterator to mid would be invalidated every time an insertion in the front half of the vector occurs -- though this program doesn't do it, it could be invalidated after any operation that changes the size of the container.

One way to handle this would be removing the need to access the mid iterator any time after the loop starts:

std::vector<int>::iterator iter = iv.begin();

for (std::vector<int>::size_type cnt = iv.size()/2; cnt != 0; --cnt) {
  if (*iter == some_val) {
    iter = iv.insert(iter, 2 * some_val);
    ++iter;
  }
  ++iter;
}