fact: Fixpoint nth {A} (n : nat) (l : mlist A) : t A := match n, l with | 0, a :m: _ => ret a | S n, _ :m: s => nth n s | _, _ => raise NotThatManyElements end.
imports: Strings.String NArith.BinNat Mtac2(Logic Datatypes Logic List Utils MTele Pattern Specif)