unit MyClasses;

interface

type
  T = Char;

  PNode = ^Node;
  Node = record
     Info:Char;
     Next:PNode;
  end;

  TStack = class
  private
    FNode:PNode;
  public
    function Empty:Boolean;
    procedure Push(Value:T);
    procedure Pop(var Value: T);
    constructor Create;
    destructor Destroy; override;
end;

implementation

constructor TStack.Create;
 begin
   inherited;
   FNode:=nil;
 end;

destructor TStack.Destroy;
var Value: T;
begin
  while (not Empty) do Pop (Value);
  inherited;
end;

function TStack.Empty:Boolean;
 begin
   if FNode=nil then Result:=true
   else Result:=false;
 end;

procedure TStack.Push(Value: T);
var P:PNode;
begin
  new(P);
  P.Next:=FNode;
  FNode:=P;
  P.Info:=Value;
end;

procedure TStack.Pop (var Value: T);
var P:PNode;
begin
  if not Empty then
  begin
    P:=FNode;
    FNode:=P.Next;
    Value:=P.Info;
    dispose(P);
  end;
end;

end.