-- filename: listndbl.ads 2:53PM  9/1/95
-- child of list package, defines doubly-linked lists as derived 
-- from singly-linked lists

generic
  --type element is private;	the generic parameter is declared
  --				for list package, this is just a reminder
package listn.dbl is

procedure insert(value:in element; 
                 afterX, inList: in out pointer);

function cons(x:in element; toList : in pointer) return pointer;

function prev(DL : in pointer) return pointer;

procedure delete(x, precededByY, inList: in out pointer);

private

  type dlistnode is new listnode with
     record
       previous: pointer;
     end record;
end listn.dbl;