proposition: Lemma nth_opt_None : forall sz (v : ByteBuffer.t sz) idx, le sz idx -> nth_opt v idx = None.
proof: Proof. induction v; simpl; intros. - destruct idx; simpl; try reflexivity. - inversion H; subst. + eapply IHv; eauto. + eapply IHv; Omega.omega. Qed.
imports: Fiat.Common.Coq__8_4__8_5__Compat Coq.Strings.String Coq.Arith.Mult Coq.Vectors.Vector Fiat.Common.SumType Fiat.Common.BoundedLookup Fiat.Common.ilist Fiat.Common.DecideableEnsembles Fiat.Common.IterateBoundedIndex Fiat.Common.Tactics.CacheStringConstant Fiat.Computation Fiat.Narcissus.Common.Specs Fiat.Narcissus.Common.ComposeOpt Fiat.Narcissus.Formats.WordOpt Fiat.Narcissus.Formats.NatOpt Fiat.Narcissus.Formats.StringOpt Fiat.Narcissus.Formats.EnumOpt Fiat.Narcissus.Formats.FixListOpt Fiat.Narcissus.Formats.SumTypeOpt Fiat.Narcissus.Formats.DomainNameOpt Fiat.Narcissus.Formats.Vector Fiat.Narcissus.BinLib.AlignedByteString Fiat.Narcissus.BinLib.AlignWord Fiat.Narcissus.BinLib.AlignedDecoders Fiat.Narcissus.BinLib.AlignedEncodeMonad Fiat.Narcissus.BinLib.AlignedDecodeMonad Fiat.Narcissus.BinLib.AlignedList Fiat.Narcissus.BaseFormats Bedrock.Word