(* split factorized denominators *)
Fixpoint Fcons00 (e:PExpr C) (l:list (PExpr C)) {struct e} : list (PExpr C) :=
match e with
PEmul e1 e2 => Fcons00 e1 (Fcons00 e2 l)
| PEpow e1 _ => Fcons00 e1 l
| _ => Fcons0 e l
end.

Theorem PFcons00_fcons_inv:
forall l a l1, PCond l (Fcons00 a l1) -> ~ a @ l == 0 /\ PCond l l1.