Section Append.
Variable (K : ordType) (V : Type).
Notation fmap := (finMap K V).
Notation nil := (nil K V).

(* forward induction principle *)
Lemma fmap_ind' (P : fmap -> Prop) :
P nil -> (forall k v s, path ord k (supp s) -> P s -> P (ins k v s)) ->
forall s, P s.