proposition: Fact append_rr_match ll lx lr rl rx rr : rspec (fun a x b => Rd (Rd ll lx a) x (Rd b rx rr)) (fun t => Rd ll lx (Rd t rx rr)) (append lr rl) (append (Rd ll lx lr) (Rd rl rx rr)).
proof: Proof. exact (rmatch _ _ _). Qed.
imports: Bool List BinPos Pnat Setoid SetoidList PeanoNat