(* Properties concerning basic local environment slicing ********************)
-lemma drops_drop_trans: â\88\80L1,L,des. â\87©*[â\92», des] L1 â\89¡ L â\86\92 â\88\80L2,i. â\87©[i] L ≡ L2 →
- â\88\83â\88\83L0,des0,i0. â\87©[i0] L1 â\89¡ L0 & â\87©*[Ⓕ, des0] L0 ≡ L2 &
+lemma drops_drop_trans: â\88\80L1,L,des. â¬\87*[â\92», des] L1 â\89¡ L â\86\92 â\88\80L2,i. â¬\87[i] L ≡ L2 →
+ â\88\83â\88\83L0,des0,i0. â¬\87[i0] L1 â\89¡ L0 & â¬\87*[Ⓕ, des0] L0 ≡ L2 &
@⦃i, des⦄ ≡ i0 & des ▭ i ≡ des0.
#L1 #L #des #H elim H -L1 -L -des
[ /2 width=7 by drops_nil, minuss_nil, at_nil, ex4_3_intro/