procedure KouchiKihou(P : PTree);
          {後置記法で書く}
  begin
    if P <> Nil
      then begin
             KouchiKihou(P^.Left);
             KouchiKihou(P^.Right);
             Write(P^.Symbol);
           end;
  end; {KouchiKihou}

または

procedure KouchiKihou(P : PTree);
          {後置記法で書く}
  begin
    if P^.Left <> Nil
      then KouchiKihou(P^.Left);
    if P^.Right <> Nil
      then KouchiKihou(P^.Right);
    Write(P^.Symbol);
  end; {KouchiKihou}