let hybrid g () = (sin, cos) where
  rec der sin = cos init 0.0
  and der cos = -. sin init 1.0

let hybrid f () =
  let der t = 1.0 init 0.0 in
  let sin, cos = g () in
  let z = period (0.01) in
  present z -> (
    print_float t;
    print_string "\t";
    print_float sin;
    print_string "\t";
    print_float cos;
    print_newline ()
  ); ()