proposition: Lemma inj_max n m : 0<=n -> 0<=m -> Z.abs_nat (Z.max n m) = Nat.max (Z.abs_nat n) (Z.abs_nat m).
proof: Proof. intros. now rewrite <- !Zabs_N_nat, Zabs2N.inj_max, N2Nat.inj_max. Qed.
imports: Arith_base BinPos BinInt BinNat Pnat Nnat