(**************************************************************************)
include "basic_2/relocation/lexs_length.ma".
-include "basic_2/static/lfxs.ma".
+include "basic_2/static/lfxs_drops.ma".
(* GENERIC EXTENSION ON REFERRED ENTRIES OF A CONTEXT-SENSITIVE REALTION ****)
(* Forward lemmas with length for local environments ************************)
(* Basic_2A1: uses: llpx_sn_fwd_length *)
-lemma lfxs_fwd_length: â\88\80R,L1,L2,T. L1 ⦻*[R, T] L2 → |L1| = |L2|.
+lemma lfxs_fwd_length: â\88\80R,L1,L2,T. L1 ⪤*[R, T] L2 → |L1| = |L2|.
#R #L1 #L2 #T * /2 width=4 by lexs_fwd_length/
qed-.
+
+(* Properties with length for local environments ****************************)
+
+(* Basic_2A1: uses: llpx_sn_lift_le llpx_sn_lift_ge *)
+lemma lfxs_lifts_bi: ∀R.d_liftable2_sn … lifts R →
+ ∀L1,L2. |L1| = |L2| → ∀K1,K2,T. K1 ⪤*[R, T] K2 →
+ ∀b,f. ⬇*[b, f] L1 ≡ K1 → ⬇*[b, f] L2 ≡ K2 →
+ ∀U. ⬆*[f] T ≡ U → L1 ⪤*[R, U] L2.
+#R #HR #L1 #L2 #HL12 #K1 #K2 #T * #f1 #Hf1 #HK12 #b #f #HLK1 #HLK2 #U #HTU
+elim (frees_total L1 U) #f2 #Hf2
+lapply (frees_fwd_coafter … Hf2 … HLK1 … HTU … Hf1) -HTU #Hf
+/4 width=12 by lexs_length_cfull, lexs_liftable_co_dedropable_bi, cext2_d_liftable2_sn, cfull_lift_sn, ex2_intro/
+qed-.