--- /dev/null
+(**************************************************************************)
+(* ___ *)
+(* ||M|| *)
+(* ||A|| A project by Andrea Asperti *)
+(* ||T|| *)
+(* ||I|| Developers: *)
+(* ||T|| The HELM team. *)
+(* ||A|| http://helm.cs.unibo.it *)
+(* \ / *)
+(* \ / This file is distributed under the terms of the *)
+(* v GNU General Public License Version 2 *)
+(* *)
+(**************************************************************************)
+
+include "delayed_updating/reduction/dbfr.ma".
+
+include "delayed_updating/substitution/fsubst_lift.ma".
+include "delayed_updating/substitution/fsubst_eq.ma".
+include "delayed_updating/substitution/lift_constructors.ma".
+include "delayed_updating/substitution/lift_path_structure.ma".
+include "delayed_updating/substitution/lift_path_closed.ma".
+include "delayed_updating/substitution/lift_rmap_closed.ma".
+
+(* DELAYED BALANCED FOCUSED REDUCTION ***************************************)
+
+(* Constructions with lift **************************************************)
+
+theorem dbfr_lift_bi (f) (t1) (t2) (r):
+ t1 โก๐๐๐[r] t2 โ ๐ ก[f]t1 โก๐๐๐[๐ ก[f]r] ๐ ก[f]t2.
+#f #t1 #t2 #r
+* #p #b #q #m #n #Hr #Hb #Hm #Hn #Ht1 #Ht2 destruct
+@(ex6_5_intro โฆ (๐ ก[f]p) (๐ ก[๐ ข[f](pโ๐)]b) (๐ ก[๐ ข[f](pโ๐โbโ๐)]q) (๐ ข[f](pโ๐โb)๏ผ โจmโฉ) (๐ ข[f](pโ๐โbโ๐โq)๏ผ ยงโจnโฉ))
+[ -Hb -Hm -Hn -Ht1 -Ht2 //
+| -Hm -Hn -Ht1 -Ht2 //
+| -Hb -Hn -Ht1 -Ht2
+ /2 width=1 by lift_path_closed/
+| -Hb -Hm -Ht1 -Ht2
+ /2 width=1 by lift_path_rmap_closed_L/
+| lapply (in_comp_lift_path_term f โฆ Ht1) -Ht2 -Ht1 -Hn
+ <lift_path_d_dx #Ht1 //
+| lapply (lift_term_eq_repl_dx f โฆ Ht2) -Ht2 #Ht2 -Ht1
+ @(subset_eq_trans โฆ Ht2) -t2
+ @(subset_eq_trans โฆ (lift_term_fsubst โฆ))
+ @fsubst_eq_repl [ // | // ]
+ @(subset_eq_trans โฆ (lift_term_iref_nap โฆ))
+ <list_append_rcons_sn <list_append_rcons_sn >list_append_assoc
+ >(nap_plus_lift_rmap_append_closed_Lq_dx โฆ Hn)
+ @iref_eq_repl
+ @(subset_eq_canc_sn โฆ (lift_term_grafted_S โฆ))
+ @lift_term_eq_repl_sn
+(* Note: crux of the proof begins *)
+ >lift_rmap_A_dx
+ /2 width=2 by tls_succ_plus_lift_rmap_append_closed_bLq_dx/
+(* Note: crux of the proof ends *)
+]
+qed.