proposition: Lemma IS_absorb : forall f, IS (E# @ R) f -> EIS R.
proof: Proof. intros f hf. destruct (ISComp_split hf) as [g H]. exists g. intro i. ded (H i). ded (H (S i)). eapply absorbs_right_rtc. apply ab. exists (f (S i)). intuition. Qed.
imports: CoLoR(RelUtil NatUtil Path LeastNat LogicUtil ClassicUtil SN NotSN_IS SortUtil ListUtil) Coq(IndefiniteDescription)