{A : Type} {g : A -> A} (p : forall x, x = g x) {x y : A} (q : x = y) {w z : A} (r : w = x) (s : g y = z) : (r @ p x) @ (ap g q @ s) = (r @ q) @ (p y @ s). Proof. destruct q, s; simpl. induction (p x). reflexivity. Defined.
Require Import Basics.Overture Basics.Tactics.