Definition Pphi_pow :=
   let mkpow x p :=
      match p with xH => x | _ => rpow x (Cp_phi (Npos p)) end in
   let mkopp_pow x p := ropp (mkpow x p)  in
   let mkmult_pow r x p := rmul r (mkpow x p) in
    Pphi_avoid mkpow mkopp_pow mkmult_pow.

Lemma local_mkpow_ok r p : match p with | xI _ => rpow r (Cp_phi (Npos p)) | xO _ => rpow r (Cp_phi (Npos p)) | 1 => r end == pow_pos rmul r p.