fact: Fixpoint Nwmul (w1 w2 : Nword) {struct w1} : Nword := match w1 with | 0%N::w1' => Nwopp (Nwmul w1' w2) | n1::w1' => Nwsub (Nwscal n1 w2) (Nwmul w1' w2) | nil => nil end.
imports: Zbool BinInt BinNat Setoid Ring_theory Ring_polynom