fact: Definition hd : forall {A : Type} {n : nat}, t A (S n) -> A := fun A n v => match v in t _ m return match m with O => Unit | S _ => A end with | nil => tt | cons _ a _ => a end.
imports: Coq(ssreflect) HoTT(HoTT) HoTT_additions Hierarchy Param_nat