Section Fcons_simpl.
(* Some general simpifications of the condition: eliminate duplicates, split multiplications *)
Fixpoint Fcons (e:PExpr C) (l:list (PExpr C)) {struct l} : list (PExpr C) :=
match l with
nil       => cons e nil
| cons a l1 => if PExpr_eq e a then l else cons a (Fcons e l1)
end.
(* equality of normal forms rather than syntactic equality *)
Fixpoint Fcons0 (e:PExpr C) (l:list (PExpr C)) {struct l} : list (PExpr C) :=
match l with
nil       => cons e nil
| cons a l1 =>
if Peq ceqb (Nnorm O nil e) (Nnorm O nil a) then l
else cons a (Fcons0 e l1)
end.
(* 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.