End maps.
Infix "=_M" := Ext (at level 70).
Infix "==>" := Map_setoid (at level 95, right associativity).
(* Identity Map *)
Section id_map_def.
Variable A : Setoid.
Definition Id_fun (x : A) := x.

(* Specifications: *)
Lemma Id_fun_map_law : Map_law Id_fun.
Canonical Structure Id_map : Map A A := Id_fun_map_law.