let pp_bkind fmt bk = match bk with
| Bfct -> Format.fprintf fmt "fct"
| Bstmt s -> Format.fprintf fmt "stmt:%d" s.sid
| Bthen s -> Format.fprintf fmt "then:%d" s.sid
| Belse s -> Format.fprintf fmt "else:%d" s.sid
| Bloop s -> Format.fprintf fmt "loop:%d" s.sid