(** ** Recursion operator *)
Definition C := .\ "x", "y"; "y" (.\ "z"; "x" "x" "y" "z").
Definition rho s : term := Eval cbv in .\ "x" ; C C !s "x".

Lemma uniform_confluence s t1 t2 :
s ≻ t1 -> s ≻ t2 -> t1 = t2 \/ exists u, t1 ≻ u /\ t2 ≻ u.