-- filename: liststac.ads 2:15PM  9/1/95
-- the generic parameter to list (and thus list.stacks) is the 
-- Element type (which is private)
-- note that since list.stacks is a child package it has access to
-- all the private information of the list package. Thus one COULD,
-- though perhaps one shouldn't, make direct use of the 
-- representation of lists, accessing parts of listnodes.

with list;
generic
package list.stacks is

type Stack is new pointer; 

procedure MkEmpty(S:in out Stack);

procedure push(x:in element; onStk:in out Stack);

function TopOf(S: in Stack)return element renames first;

procedure pop(S: in out Stack);

procedure Copy(S1: in Stack; S2: in out Stack);

procedure MkSame(S1: in Stack; S2: in out Stack);

--function IsEmpty(S: in Stack) return Boolean; 
--inherited from list

--function IsEqual(S1,S2: in Stack) return Boolean; 
--inherited from list

function IsSame(S1,S2: in Stack) return Boolean;

Underflow :exception renames NoElements;
Overflow: exception;


end list.stacks;