let x =
match y with
| A z -> z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z z
| B l ->
(match l with
| [] -> ()
| x::xs -> p x; self xs)
| C -> ()
in x