proposition: Lemma euttG_ret: forall rH rL gL gH v1 v2, RR v1 v2 -> euttG rH rL gL gH (Ret v1) (Ret v2).
proof: Proof. econstructor. gstep. econstructor. eauto. Qed.
imports: Coq(Setoid Morphisms Relations) Paco(paco) ITree(Basics.Utils Core.ITreeDefinition Eq.Eqit Eq.Paco2 Eq.Shallow)