list.s.r = clone(list.s.r)
This function is used as a constructor to create a copy of a
pre-existing instance of the List class. The new instance will
be identical to the original instance in all respects, except
that it will use different storage - therefore operations on the
original instance will not affect the new instance, and vice-versa.
list a pointer to the list (structure of type List)
This function returns:
a pointer to the newly-created instance of the List class upon
success, or a null pointer upon failure to allocate virtual memory.
Use of this class requires the following header files:
create_List() the constructor for instances of the List class
list_2 = (*list_1->clone)(list_1);