-lemma dfr_lift_bi (f) (p) (q) (t1) (t2): t1 Ο΅ π β
- t1 β‘ππ[p,q] t2 β β[f]t1 β‘π[βp,βq] β[f]t2.
-#f #p #q #t1 #t2 #H0t1
-* #b #n * #Hb #Hn #Ht1 #Ht2
-@(ex1_2_intro β¦ (βb) (βββqβ)) @and4_intro
-[ //
-| #g <lift_rmap_structure <depth_structure
- >tr_pushs_swap <tr_pap_pushs_le //
-| lapply (in_comp_lift_bi f β¦ Ht1) -Ht1 -H0t1 -Hb -Ht2
- <lift_path_d_empty_dx //
-| lapply (lift_term_eq_repl_dx f β¦ Ht2) -Ht2 #Ht2
+(* Main destructions with ifr ***********************************************)
+
+theorem dfr_des_ifr (f) (t1) (t2) (r): t1 Ο΅ π β
+ t1 β‘ππ[r] t2 β βΌ[f]t1 β‘π’π[βr] βΌ[f]t2.
+#f #t1 #t2 #r #H0t1
+* #p #q #n #Hr #Hn #Ht1 #Ht2 destruct
+@(ex4_3_intro β¦ (βp) (βq) (βq))
+[ -H0t1 -Hn -Ht1 -Ht2 //
+| -H0t1 -Ht1 -Ht2
+ /2 width=2 by path_closed_structure_depth/
+| lapply (in_comp_unwind2_path_term f β¦ Ht1) -Ht2 -Ht1 -H0t1
+ <unwind2_path_d_dx <tr_pap_succ_nap <list_append_rcons_sn
+ <nap_unwind2_rmap_append_closed_Lq_dx_depth //
+| lapply (unwind2_term_eq_repl_dx f β¦ Ht2) -Ht2 #Ht2