--- /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 "basic_2A/substitution/lift_neg.ma".
+include "basic_2A/substitution/lift_lift.ma".
+include "basic_2A/substitution/cpy.ma".
+
+(* CONTEXT-SENSITIVE EXTENDED ORDINARY SUBSTITUTION FOR TERMS ***************)
+
+(* Inversion lemmas on negated relocation ***********************************)
+
+lemma cpy_fwd_nlift2_ge: ∀G,L,U1,U2,l,m. ⦃G, L⦄ ⊢ U1 ▶[l, m] U2 →
+ ∀i. l ≤ yinj i → (∀T2. ⬆[i, 1] T2 ≡ U2 → ⊥) →
+ (∀T1. ⬆[i, 1] T1 ≡ U1 → ⊥) ∨
+ ∃∃I,K,W,j. l ≤ yinj j & j < i & ⬇[j]L ≡ K.ⓑ{I}W &
+ (∀V. ⬆[i-j-1, 1] V ≡ W → ⊥) & (∀T1. ⬆[j, 1] T1 ≡ U1 → ⊥).
+#G #L #U1 #U2 #l #m #H elim H -G -L -U1 -U2 -l -m
+[ /3 width=2 by or_introl/
+| #I #G #L #K #V #W #j #l #m #Hlj #Hjlm #HLK #HVW #i #Hli #HnW
+ elim (lt_or_ge j i) #Hij
+ [ @or_intror @(ex5_4_intro … HLK) // -HLK
+ [ #X #HXV elim (lift_trans_le … HXV … HVW ?) -V //
+ #Y #HXY >minus_plus <plus_minus_m_m /2 width=2 by/
+ | -HnW /2 width=7 by lift_inv_lref2_be/
+ ]
+ | elim (lift_split … HVW i j) -HVW //
+ #X #_ #H elim HnW -HnW //
+ ]
+| #a #I #G #L #W1 #W2 #U1 #U2 #l #m #_ #_ #IHW12 #IHU12 #i #Hli #H elim (nlift_inv_bind … H) -H
+ [ #HnW2 elim (IHW12 … HnW2) -IHW12 -HnW2 -IHU12 //
+ [ /4 width=9 by nlift_bind_sn, or_introl/
+ | * /5 width=9 by nlift_bind_sn, ex5_4_intro, or_intror/
+ ]
+ | #HnU2 elim (IHU12 … HnU2) -IHU12 -HnU2 -IHW12 /2 width=1 by yle_succ/
+ [ /4 width=9 by nlift_bind_dx, or_introl/
+ | * #J #K #W #j #Hlj #Hji #HLK #HnW
+ elim (yle_inv_succ1 … Hlj) -Hlj #Hlj #Hj
+ lapply (ylt_O … Hj) -Hj #Hj
+ lapply (drop_inv_drop1_lt … HLK ?) // -HLK #HLK
+ >(plus_minus_m_m j 1) in ⊢ (%→?); [2: /3 width=3 by yle_trans, yle_inv_inj/ ]
+ #HnU1 <minus_le_minus_minus_comm in HnW;
+ /5 width=9 by nlift_bind_dx, monotonic_lt_pred, lt_plus_to_minus_r, ex5_4_intro, or_intror/
+ ]
+ ]
+| #I #G #L #W1 #W2 #U1 #U2 #l #m #_ #_ #IHW12 #IHU12 #i #Hli #H elim (nlift_inv_flat … H) -H
+ [ #HnW2 elim (IHW12 … HnW2) -IHW12 -HnW2 -IHU12 //
+ [ /4 width=9 by nlift_flat_sn, or_introl/
+ | * /5 width=9 by nlift_flat_sn, ex5_4_intro, or_intror/
+ ]
+ | #HnU2 elim (IHU12 … HnU2) -IHU12 -HnU2 -IHW12 //
+ [ /4 width=9 by nlift_flat_dx, or_introl/
+ | * /5 width=9 by nlift_flat_dx, ex5_4_intro, or_intror/
+ ]
+]
+qed-.