Notation ring_rw_correct :=
(ring_rw_correct Rsth Reqe ARth CRmorph pow_th cdiv_th get_sign_spec).
Notation ring_rw_pow_correct :=
(ring_rw_pow_correct Rsth Reqe ARth CRmorph pow_th cdiv_th get_sign_spec).
Notation ring_correct :=
(ring_correct Rsth Reqe ARth CRmorph pow_th cdiv_th).
(* simplify a field expression into a fraction *)
Definition display_linear l num den :=
let lnum := NPphi_dev l num in
match den with
| Pc c => if ceqb c cI then lnum else lnum / NPphi_dev l den
| _ => lnum / NPphi_dev l den
end.
Definition display_pow_linear l num den :=
let lnum := NPphi_pow l num in
match den with
| Pc c => if ceqb c cI then lnum else lnum / NPphi_pow l den
| _ => lnum / NPphi_pow l den
end.

Theorem Field_rw_correct n lpe l :
Ninterp_PElist l lpe ->
forall lmp, Nmk_monpol_list lpe = lmp ->
forall fe nfe, Fnorm fe = nfe ->
PCond l (condition nfe) ->
FEeval l fe ==
display_linear l (Nnorm n lmp (num nfe)) (Nnorm n lmp (denum nfe)).