fact: Fixpoint append_word {n m} (w : word n) (w' : word m) : word (n + m) := match n return word n -> word (n + m) with | 0 => fun _ => w' | S n' => fun w => WS (whd w) (append_word (wtl w) w') end w.
imports: Fiat.Common.Coq__8_4__8_5__Compat Bedrock.Word Coq.ZArith.ZArith Coq.NArith.NArith Coq.Arith.Arith Coq.Numbers.Natural.Peano.NPeano Coq.Logic.Eqdep_dec Fiat.Narcissus.Common.Specs