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/substitution/leq_defs.ma".
13 include "lambda-delta/substitution/lift_defs.ma".
15 (* DROPPING *****************************************************************)
17 inductive drop: lenv → nat → nat → lenv → Prop ≝
18 | drop_refl: ∀L. drop L 0 0 L
19 | drop_drop: ∀L1,L2,I,V,e. drop L1 0 e L2 → drop (L1. 𝕓{I} V) 0 (e + 1) L2
20 | drop_skip: ∀L1,L2,I,V1,V2,d,e.
21 drop L1 d e L2 → ↑[d,e] V2 ≡ V1 →
22 drop (L1. 𝕓{I} V1) (d + 1) e (L2. 𝕓{I} V2)
25 interpretation "dropping" 'RDrop L1 d e L2 = (drop L1 d e L2).
27 (* Basic inversion lemmas ***************************************************)
29 lemma drop_inv_refl_aux: ∀d,e,L1,L2. ↓[d, e] L1 ≡ L2 → d = 0 → e = 0 → L1 = L2.
30 #d #e #L1 #L2 * -d e L1 L2
32 | #L1 #L2 #I #V #e #_ #_ #H
33 elim (plus_S_eq_O_false … H)
34 | #L1 #L2 #I #V1 #V2 #d #e #_ #_ #H
35 elim (plus_S_eq_O_false … H)
39 lemma drop_inv_refl: ∀L1,L2. ↓[0, 0] L1 ≡ L2 → L1 = L2.
42 lemma drop_inv_sort1_aux: ∀d,e,L1,L2. ↓[d, e] L1 ≡ L2 → L1 = ⋆ →
43 ∧∧ L2 = ⋆ & d = 0 & e = 0.
44 #d #e #L1 #L2 * -d e L1 L2
46 | #L1 #L2 #I #V #e #_ #H destruct
47 | #L1 #L2 #I #V1 #V2 #d #e #_ #_ #H destruct
51 lemma drop_inv_sort1: ∀d,e,L2. ↓[d, e] ⋆ ≡ L2 →
52 ∧∧ L2 = ⋆ & d = 0 & e = 0.
55 lemma drop_inv_O1_aux: ∀d,e,L1,L2. ↓[d, e] L1 ≡ L2 → d = 0 →
56 ∀K,I,V. L1 = K. 𝕓{I} V →
57 (e = 0 ∧ L2 = K. 𝕓{I} V) ∨
58 (0 < e ∧ ↓[d, e - 1] K ≡ L2).
59 #d #e #L1 #L2 * -d e L1 L2
61 | #L1 #L2 #I #V #e #HL12 #_ #K #J #W #H destruct -L1 I V /3/
62 | #L1 #L2 #I #V1 #V2 #d #e #_ #_ #H elim (plus_S_eq_O_false … H)
66 lemma drop_inv_O1: ∀e,K,I,V,L2. ↓[0, e] K. 𝕓{I} V ≡ L2 →
67 (e = 0 ∧ L2 = K. 𝕓{I} V) ∨
68 (0 < e ∧ ↓[0, e - 1] K ≡ L2).
71 lemma drop_inv_drop1: ∀e,K,I,V,L2.
72 ↓[0, e] K. 𝕓{I} V ≡ L2 → 0 < e → ↓[0, e - 1] K ≡ L2.
73 #e #K #I #V #L2 #H #He
74 elim (drop_inv_O1 … H) -H * // #H destruct -e;
75 elim (lt_refl_false … He)
78 lemma drop_inv_skip2_aux: ∀d,e,L1,L2. ↓[d, e] L1 ≡ L2 → 0 < d →
79 ∀I,K2,V2. L2 = K2. 𝕓{I} V2 →
80 ∃∃K1,V1. ↓[d - 1, e] K1 ≡ K2 &
83 #d #e #L1 #L2 * -d e L1 L2
84 [ #L #H elim (lt_refl_false … H)
85 | #L1 #L2 #I #V #e #_ #H elim (lt_refl_false … H)
86 | #L1 #X #Y #V1 #Z #d #e #HL12 #HV12 #_ #I #L2 #V2 #H destruct -X Y Z;
91 lemma drop_inv_skip2: ∀d,e,I,L1,K2,V2. ↓[d, e] L1 ≡ K2. 𝕓{I} V2 → 0 < d →
92 ∃∃K1,V1. ↓[d - 1, e] K1 ≡ K2 & ↑[d - 1, e] V2 ≡ V1 &
96 (* Basic properties *********************************************************)
98 lemma drop_drop_lt: ∀L1,L2,I,V,e.
99 ↓[0, e - 1] L1 ≡ L2 → 0 < e → ↓[0, e] L1. 𝕓{I} V ≡ L2.
100 #L1 #L2 #I #V #e #HL12 #He >(plus_minus_m_m e 1) /2/
103 lemma drop_fwd_drop2: ∀L1,I2,K2,V2,e. ↓[O, e] L1 ≡ K2. 𝕓{I2} V2 →
106 [ #I2 #K2 #V2 #e #H elim (drop_inv_sort1 … H) -H #H destruct
107 | #K1 #I1 #V1 #IHL1 #I2 #K2 #V2 #e #H
108 elim (drop_inv_O1 … H) -H * #He #H
109 [ -IHL1; destruct -e K2 I2 V2 /2/
110 | @drop_drop >(plus_minus_m_m e 1) /2/
115 lemma drop_leq_drop1: ∀L1,L2,d,e. L1 [d, e] ≈ L2 →
116 ∀I,K1,V,i. ↓[0, i] L1 ≡ K1. 𝕓{I} V →
118 ∃∃K2. K1 [0, d + e - i - 1] ≈ K2 &
119 ↓[0, i] L2 ≡ K2. 𝕓{I} V.
120 #L1 #L2 #d #e #H elim H -H L1 L2 d e
121 [ #d #e #I #K1 #V #i #H
122 elim (drop_inv_sort1 … H) -H #H destruct
123 | #L1 #L2 #I1 #I2 #V1 #V2 #_ #_ #I #K1 #V #i #_ #_ #H
124 elim (lt_zero_false … H)
125 | #L1 #L2 #I #V #e #HL12 #IHL12 #J #K1 #W #i #H #_ #Hie
126 elim (drop_inv_O1 … H) -H * #Hi #HLK1
127 [ -IHL12 Hie; destruct -i K1 J W;
128 <minus_n_O <minus_plus_m_m /2/
130 elim (IHL12 … HLK1 ? ?) -IHL12 HLK1 // [2: /2/ ] -Hie >arith_g1 // /3/
132 | #L1 #L2 #I1 #I2 #V1 #V2 #d #e #_ #IHL12 #I #K1 #V #i #H #Hdi >plus_plus_comm_23 #Hide
133 lapply (plus_S_le_to_pos … Hdi) #Hi
134 lapply (drop_inv_drop1 … H ?) -H // #HLK1
135 elim (IHL12 … HLK1 ? ?) -IHL12 HLK1 [2: /2/ |3: /2/ ] -Hdi Hide >arith_g1 // /3/