Require Export FunctionProperties.
Require Export Ensembles.
Require Export EnsemblesSpec.
Definition inverse_image {X Y:Type} (f:X->Y) (T:Ensemble Y) : Ensemble X :=
[ x:X | In T (f x) ].
Hint Unfold inverse_image : sets.
Hint Resolve @inverse_image_increasing : sets.
Hint Rewrite @inverse_image_empty @inverse_image_full
@inverse_image_intersection @inverse_image_union
@inverse_image_complement @inverse_image_composition : sets.

Lemma inverse_image_id
{X Y : Type}
{f : X -> Y}
{g : Y -> X} :
(forall y, f (g y) = y) ->
forall S,
inverse_image g (inverse_image f S) = S.