// Fibonacci sequence in D4 (Dataphor)
create operator Fibonacci(const n : Integer) : Integer
begin
  if n <= 1 then
    result := n
  else
    result := Fibonacci(n - 1) + Fibonacci(n - 2);
end;

begin
  var i : Integer;
  var line : String;
  for i := 0 to 9 do
  begin
    line := 'Fibonacci(' + i.ToString() + ') = ' + Fibonacci(i).ToString();
    SystemMessage(line);
  end;
end;