The following code example is taken from the book
C++ Templates - The Complete Guide, 2nd Edition
by David Vandevoorde, Nicolai M. Josuttis, and Douglas Gregor,
Addison-Wesley, 2017
© Copyright David Vandevoorde, Nicolai M. Josuttis, Douglas Gregor 2017
template<typename Iter, typename Callable>
void foreach (Iter current, Iter end, Callable op)
{
while (current != end) { // as long as not reached the end
op(*current); // call passed operator for current element
++current; // and move iterator to next element
}
}