Require RndHoare.axiom. Import RndHoare.axiom.NatChoice.
Fixpoint app_fin_inf {ora: RandomOracle} (l: list RandomQA) (f: nat -> RandomQA) :=
match l with
| nil => f
| qa :: l0 => fun n =>
match n with
| 0 => qa
| S m => app_fin_inf l0 f m
end
end.

Lemma nth_error_app1: forall {T} (al bl : list T) (j: nat),
(j < length al)%nat ->
nth_error (al++bl) j = nth_error al j.