let pretty fmt e =
let txt = match e with
| Enone -> "----" | Ethen -> "then" | Eelse -> "else"
| Eback -> "back" | EbackThen -> "then-back" | EbackElse -> "else-back"
| Ecase [] -> "default"
| Ecase l -> Pretty_utils.sfprintf "case(%a)"
(Pretty_utils.pp_list ~sep:", " !Ast_printer.d_exp) l
| Enext -> "(next)"
in Format.fprintf fmt "%s" txt