-- filename: list.ads 2:25PM  10/25/95
-- generic (by element type) list package with extendable listnode


generic
type element is private;
package list is

type pointer is private;

-- functions that sample but do not modify lists
--
function cons(x:in element; toList : in pointer) return pointer;

function first(ofList: in pointer) return element;

function rest(ofList: in pointer) return pointer;

function Empty return pointer;

function isEmpty(L: in pointer) return boolean;

function isEqual(L1,L2: in pointer) return boolean;

-- procedures that side effect (change the state of) lists
--

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

procedure setFirst(L: in out pointer; NewV: in Element); 

procedure setRest(L: in out pointer; NewR: in pointer);

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

NoElements, Overflow: exception;

private

type listnode;
type pointer is access listnode;
type listnode is 
  record
    data : Element;
    next : pointer;
  end record;

end list;