item.g.r = get(list.s.r)
This method returns the element at the head of the List,
removing element from the List.
list a pointer to the list (structure of type List)
This function returns:
a pointer to the item at the head of the List.
Use of this class requires the following header files:
create_List() the constructor for instances of the List class
ptr = (*list->get)(list);
if (ptr != (void *) NULL)
item = *ptr;
The List class actually allocates space in which to store the
data item given to it for the "put" operation. It is a pointer
to this allocated space that is returned by this method.
Therefore the user of the List class must be sure to free
this pointer when finished with it, or else memory leaks will