[Northern]

Cierto, ahora que lo miré un poco yo lo haría de esta manera:

Código Delphi [-]
unit uPilas;
interface
uses StdCtrls, Dialogs;
const
  maxpila=10;
type
  tipoinfo = string ;
  TPila = class(Tobject)
  private
    tope: 0..maxpila;
    items:array [1..maxpila]of tipoinfo;
  public
    constructor Create;
    function vacia: boolean;
    function llena: boolean;
    procedure insertar(x: tipoinfo);
    function eliminar: tipoinfo;
  end;
implementation
constructor TPila.Create;
begin
  inherited Create;
  tope:=0;
end;
function TPila.vacia: boolean;
begin
  vacia := (tope = 0);
end;
function TPila.llena: boolean;
begin
  llena := (tope=maxpila);
end;
function TPila.eliminar: tipoinfo;
begin
  if vacia then
    ShowMessage('Pila vacia')
  else
  begin
    eliminar:=items[tope];
    dec(tope);
  end;
end;
procedure TPila.insertar(x: tipoinfo);
begin
  if llena then
    showmessage('Pila llena')
  else
  begin
    inc(tope);
    items[tope] := x;
  end;
end;
end.

La unit ufPilas (la del form):

Código Delphi [-]
unit ufPilas;
interface
uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;
type
  TForm1 = class(TForm)
    Label1: TLabel;
    eInsertar: TEdit;
    bInsertar: TButton;
    bEliminar: TButton;
    lbMostrar: TListBox;
    procedure FormCreate(Sender: TObject);
    procedure FormActivate(Sender: TObject);
    procedure bInsertarClick(Sender: TObject);
    procedure bEliminarClick(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
var
  Form1: TForm1;
implementation
uses uPilas;
{$R *.dfm}
var
  P: TPila;
procedure TForm1.FormCreate(Sender: TObject);
begin
  p := TPila.Create;
end;
procedure TForm1.FormActivate(Sender: TObject);
begin
  eInsertar.SetFocus;
  eInsertar.SelectAll;
end;
procedure TForm1.bInsertarClick(Sender: TObject);
begin
  if length(eInsertar.Text) = 0 then
    showmessage('texto en blanco')
  else
  begin
    lbmostrar.items.Append(eInsertar.Text);
    p.insertar(eInsertar.Text);
    eInsertar.setfocus;
    eInsertar.SelectAll;
  end;
end;
procedure TForm1.bEliminarClick(Sender: TObject);
var
  x: Tpila;
begin
  p.eliminar();
  lbmostrar.Items.delete(lbmostrar.ItemIndex);
end;
end.

Así ya funciona...eso creo


Saludos