2 ||M|| This file is part of HELM, an Hypertextual, Electronic
3 ||A|| Library of Mathematics, developed at the Computer Science
4 ||T|| Department of the University of Bologna, Italy.
7 ||A|| This file is distributed under the terms of the
8 \ / GNU General Public License Version 2
10 V_______________________________________________________________ *)
12 include "lambda-delta/language/term.ma".
14 (* RELOCATION ***************************************************************)
16 inductive lift: term → nat → nat → term → Prop ≝
17 | lift_sort : ∀k,d,e. lift (⋆k) d e (⋆k)
18 | lift_lref_lt: ∀i,d,e. i < d → lift (#i) d e (#i)
19 | lift_lref_ge: ∀i,d,e. d ≤ i → lift (#i) d e (#(i + e))
20 | lift_con2 : ∀I,V1,V2,T1,T2,d,e.
21 lift V1 d e V2 → lift T1 (d + 1) e T2 →
22 lift (♭I V1. T1) d e (♭I V2. T2)
25 interpretation "relocation" 'RLift T1 d e T2 = (lift T1 d e T2).
27 (* The basic properties *****************************************************)
29 lemma lift_lref_ge_minus: ∀d,e,i. d + e ≤ i → ↑[d,e] #(i - e) ≡ #i.
30 #d #e #i #H >(plus_minus_m_m i e) in ⊢ (? ? ? ? %) /3/
33 (* The basic inversion lemmas ***********************************************)
35 lemma lift_inv_sort2_aux: ∀d,e,T1,T2. ↑[d,e] T1 ≡ T2 → ∀k. T2 = ⋆k → T1 = ⋆k.
36 #d #e #T1 #T2 #H elim H -H d e T1 T2 //
37 [ #i #d #e #_ #k #H destruct
38 | #I #V1 #V2 #T1 #T2 #d #e #_ #_ #_ #_ #k #H destruct
42 lemma lift_inv_sort2: ∀d,e,T1,k. ↑[d,e] T1 ≡ ⋆k → T1 = ⋆k.
43 #d #e #T1 #k #H lapply (lift_inv_sort2_aux … H) /2/
46 lemma lift_inv_lref2_aux: ∀d,e,T1,T2. ↑[d,e] T1 ≡ T2 → ∀i. T2 = #i →
47 (i < d ∧ T1 = #i) ∨ (d + e ≤ i ∧ T1 = #(i - e)).
48 #d #e #T1 #T2 #H elim H -H d e T1 T2
49 [ #k #d #e #i #H destruct
50 | #j #d #e #Hj #i #Hi destruct /3/
51 | #j #d #e #Hj #i #Hi destruct <minus_plus_m_m /4/
52 | #I #V1 #V2 #T1 #T2 #d #e #_ #_ #_ #_ #i #H destruct
56 lemma lift_inv_lref2: ∀d,e,T1,i. ↑[d,e] T1 ≡ #i →
57 (i < d ∧ T1 = #i) ∨ (d + e ≤ i ∧ T1 = #(i - e)).
58 #d #e #T1 #i #H lapply (lift_inv_lref2_aux … H) /2/
61 lemma lift_inv_con22_aux: ∀d,e,T1,T2. ↑[d,e] T1 ≡ T2 →
62 ∀I,V2,U2. T2 = ♭I V2.U2 →
63 ∃V1,U1. ↑[d,e] V1 ≡ V2 ∧ ↑[d+1,e] U1 ≡ U2 ∧
65 #d #e #T1 #T2 #H elim H -H d e T1 T2
66 [ #k #d #e #I #V2 #U2 #H destruct
67 | #i #d #e #_ #I #V2 #U2 #H destruct
68 | #i #d #e #_ #I #V2 #U2 #H destruct
69 | #J #W1 #W2 #T1 #T2 #d #e #HW #HT #_ #_ #I #V2 #U2 #H destruct /5/
72 lemma lift_inv_con22: ∀d,e,T1,I,V2,U2. ↑[d,e] T1 ≡ ♭I V2. U2 →
73 ∃V1,U1. ↑[d,e] V1 ≡ V2 ∧ ↑[d+1,e] U1 ≡ U2 ∧
75 #d #e #T1 #I #V2 #U2 #H lapply (lift_inv_con22_aux … H) /2/
78 (* the main properies *******************************************************)
80 axiom lift_trans_rev: ∀d1,e1,T1,T. ↑[d1,e1] T1 ≡ T →
81 ∀d2,e2,T2. ↑[d2 + e1, e2] T2 ≡ T →
83 ∃T0. ↑[d1, e1] T0 ≡ T2 ∧ ↑[d2, e2] T0 ≡ T1.