function to copy-merge one sorted vector into another, in place

inmerge.cpp

template<typename T>
void inmerge(std::vector<T> &target, const std::vector<T> &source)
{
  target.resize(target.size() + source.size());
  auto lit = target.crbegin() + source.size(), rit = source.rbegin();
  auto lend = target.crend(), rend = source.rend();
  auto out = target.rbegin();
  while (rit != rend) {
    *(out++) = (lit != lend and *rit < *lit) ? *(lit++) : *(rit++);
  }
}