proposition: Lemma nth_enumerate A ls start idx default : nth idx (@enumerate A ls start) (start + idx, default) = (start + idx, nth idx ls default).
proof: Proof. rewrite !nth_error_nth, nth_error_enumerate. unfold option_map; break_innermost_match; reflexivity. Qed.
imports: Fiat.Common.Coq__8_4__8_5__Compat Coq.ZArith.ZArith Coq.Lists.List Coq.Lists.SetoidList Coq.Bool.Bool Fiat.Common Fiat.Common.List.Operations Fiat.Common.Equality Fiat.Common.List.FlattenList Fiat.Common.LogicFacts