OpenEuphoria

The routine_id is used as a sort of pointer-to-a-function, that you can use to tell another function to use this function for a certain operation. The custom_sort() is a great example of this - the sorting algorithm stays the same, but you can use a custom comparison function for the items being sorted. So to sort directory items by date, we need a function that compares the date fields from two directory items, and then use the routine_id of that function with custom_sort().