Section ImfsetTh.
Variables (key : unit) (K V : choiceType).
Implicit Types (f : K -> V) (g : V -> K) (A V : {fset K}).

(* Specifications: *)
Lemma imfset_id (A : {fset K}) : id @` A = A.
Lemma subset_imfset f (p q : finmempred _) : {subset p <= q} ->
imfset key f p `<=` imfset key f q.
Lemma eq_imfset (f f' : K -> V) (p q : finmempred _):
f =1 f' -> (forall x, in_mem x p = in_mem x q) ->
imfset key f p = imfset key f' q.