open Jog open Zone;;
let top = [[0; 1; 2; 3; 4]; [0; 1; 2; 4; 5]; [0; 1; 2; 5; 6]; [0; 1; 2; 6; 3]] in
let ini = ref (fun _ -> raise (OffTrack 3)) in
let bndry = Glue.morphgen (nz (fun i j -> if i=j then 0. else 1.)) top
    [([0; 1; 2; 3], (
      (fun t -> ini := t.curl; {t with curl = (fun (k, ball) -> ball)}), (fun  x -> x)))] in
    (bndry, !ini (3, Linear.iden 4));;

(* (_, [|[|0.84375; -0.15625; -0.15625; -0.978279740156157818|];
   [|-0.15625; 0.84375; -0.15625;
     -0.978279740156157818|];
   [|-0.15625; -0.15625; 0.84375; -0.978279740156157818|];
   [|0.244569935039039482; 0.244569935039039427; 0.244569935039039565;
     0.53125|]|]) *)