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4 (* ||A|| A project by Andrea Asperti *)
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7 (* ||T|| The HELM team. *)
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15 include "basic_2/unfold/cpss.ma".
17 (* CONTEXT-SENSITIVE RESTRICTED PARALLEL COMPUTATION FOR TERMS **************)
19 inductive cpqs: lenv → relation term ≝
20 | cpqs_atom : ∀I,L. cpqs L (⓪{I}) (⓪{I})
21 | cpqs_delta: ∀L,K,V,V2,W2,i.
22 ⇩[0, i] L ≡ K. ⓓV → cpqs K V V2 →
23 ⇧[0, i + 1] V2 ≡ W2 → cpqs L (#i) W2
24 | cpqs_bind : ∀a,I,L,V1,V2,T1,T2.
25 cpqs L V1 V2 → cpqs (L. ⓑ{I} V1) T1 T2 →
26 cpqs L (ⓑ{a,I} V1. T1) (ⓑ{a,I} V2. T2)
27 | cpqs_flat : ∀I,L,V1,V2,T1,T2.
28 cpqs L V1 V2 → cpqs L T1 T2 →
29 cpqs L (ⓕ{I} V1. T1) (ⓕ{I} V2. T2)
30 | cpqs_zeta : ∀L,V,T1,T,T2. cpqs (L.ⓓV) T1 T →
31 ⇧[0, 1] T2 ≡ T → cpqs L (+ⓓV. T1) T2
32 | cpqs_tau : ∀L,V,T1,T2. cpqs L T1 T2 → cpqs L (ⓝV. T1) T2
35 interpretation "context-sensitive restricted parallel computation (term)"
36 'PRestStar L T1 T2 = (cpqs L T1 T2).
38 (* Basic properties *********************************************************)
40 (* Note: it does not hold replacing |L1| with |L2| *)
41 lemma cpqs_lsubr_trans: ∀L1,T1,T2. L1 ⊢ T1 ➤* T2 →
42 ∀L2. L2 ⊑ [0, |L1|] L1 → L2 ⊢ T1 ➤* T2.
43 #L1 #T1 #T2 #H elim H -L1 -T1 -T2
45 | #L1 #K1 #V1 #V2 #W2 #i #HLK1 #_ #HVW2 #IHV12 #L2 #HL12
46 lapply (ldrop_fwd_ldrop2_length … HLK1) #Hi
47 lapply (ldrop_fwd_O1_length … HLK1) #H2i
48 elim (ldrop_lsubr_ldrop2_abbr … HL12 … HLK1 ? ?) -HL12 -HLK1 // -Hi
49 <H2i -H2i <minus_plus_m_m /3 width=6/
56 lemma cpss_cpqs: ∀L,T1,T2. L ⊢ T1 ▶* T2 → L ⊢ T1 ➤* T2.
57 #L #T1 #T2 #H elim H -L -T1 -T2 // /2 width=1/ /2 width=6/
60 lemma cpqs_refl: ∀T,L. L ⊢ T ➤* T.
63 lemma cpqs_delift: ∀L,K,V,T1,d. ⇩[0, d] L ≡ (K. ⓓV) →
64 ∃∃T2,T. L ⊢ T1 ➤* T2 & ⇧[d, 1] T ≡ T2.
66 elim (cpss_delift … T1 … HLK) -HLK /3 width=4/
69 lemma cpqs_append: l_appendable_sn … cpqs.
70 #K #T1 #T2 #H elim H -K -T1 -T2 // /2 width=1/ /2 width=3/
71 #K #K0 #V1 #V2 #W2 #i #HK0 #_ #HVW2 #IHV12 #L
72 lapply (ldrop_fwd_ldrop2_length … HK0) #H
73 @(cpqs_delta … (L@@K0) V1 … HVW2) //
74 @(ldrop_O1_append_sn_le … HK0) /2 width=2/ (**) (* /3/ does not work *)
77 (* Basic inversion lemmas ***************************************************)
79 fact cpqs_inv_atom1_aux: ∀L,T1,T2. L ⊢ T1 ➤* T2 → ∀I. T1 = ⓪{I} →
81 ∃∃K,V,V2,i. ⇩[O, i] L ≡ K. ⓓV &
85 #L #T1 #T2 * -L -T1 -T2
86 [ #I #L #J #H destruct /2 width=1/
87 | #L #K #V #V2 #T2 #i #HLK #HV2 #HVT2 #J #H destruct /3 width=8/
88 | #a #I #L #V1 #V2 #T1 #T2 #_ #_ #J #H destruct
89 | #I #L #V1 #V2 #T1 #T2 #_ #_ #J #H destruct
90 | #L #V #T1 #T #T2 #_ #_ #J #H destruct
91 | #L #V #T1 #T2 #_ #J #H destruct
95 lemma cpqs_inv_atom1: ∀I,L,T2. L ⊢ ⓪{I} ➤* T2 →
97 ∃∃K,V,V2,i. ⇩[O, i] L ≡ K. ⓓV &
101 /2 width=3 by cpqs_inv_atom1_aux/ qed-.
103 lemma cpqs_inv_sort1: ∀L,T2,k. L ⊢ ⋆k ➤* T2 → T2 = ⋆k.
105 elim (cpqs_inv_atom1 … H) -H //
106 * #K #V #V2 #i #_ #_ #_ #H destruct
109 lemma cpqs_inv_lref1: ∀L,T2,i. L ⊢ #i ➤* T2 →
111 ∃∃K,V,V2. ⇩[O, i] L ≡ K. ⓓV &
115 elim (cpqs_inv_atom1 … H) -H /2 width=1/
116 * #K #V #V2 #j #HLK #HV2 #HVT2 #H destruct /3 width=6/
119 lemma cpqs_inv_gref1: ∀L,T2,p. L ⊢ §p ➤* T2 → T2 = §p.
121 elim (cpqs_inv_atom1 … H) -H //
122 * #K #V #V2 #i #_ #_ #_ #H destruct
125 fact cpqs_inv_bind1_aux: ∀L,U1,U2. L ⊢ U1 ➤* U2 →
126 ∀a,I,V1,T1. U1 = ⓑ{a,I} V1. T1 → (
127 ∃∃V2,T2. L ⊢ V1 ➤* V2 &
128 L. ⓑ{I} V1 ⊢ T1 ➤* T2 &
131 ∃∃T. L.ⓓV1 ⊢ T1 ➤* T & ⇧[0, 1] U2 ≡ T & a = true & I = Abbr.
132 #L #U1 #U2 * -L -U1 -U2
133 [ #I #L #b #J #W1 #U1 #H destruct
134 | #L #K #V #V2 #W2 #i #_ #_ #_ #b #J #W1 #U1 #H destruct
135 | #a #I #L #V1 #V2 #T1 #T2 #HV12 #HT12 #b #J #W1 #U1 #H destruct /3 width=5/
136 | #I #L #V1 #V2 #T1 #T2 #_ #_ #b #J #W1 #U1 #H destruct
137 | #L #V #T1 #T #T2 #HT1 #HT2 #b #J #W1 #U1 #H destruct /3 width=3/
138 | #L #V #T1 #T2 #_ #b #J #W1 #U1 #H destruct
142 lemma cpqs_inv_bind1: ∀a,I,L,V1,T1,U2. L ⊢ ⓑ{a,I} V1. T1 ➤* U2 → (
143 ∃∃V2,T2. L ⊢ V1 ➤* V2 &
144 L. ⓑ{I} V1 ⊢ T1 ➤* T2 &
147 ∃∃T. L.ⓓV1 ⊢ T1 ➤* T & ⇧[0, 1] U2 ≡ T & a = true & I = Abbr.
148 /2 width=3 by cpqs_inv_bind1_aux/ qed-.
150 lemma cpqs_inv_abbr1: ∀a,L,V1,T1,U2. L ⊢ ⓓ{a} V1. T1 ➤* U2 → (
151 ∃∃V2,T2. L ⊢ V1 ➤* V2 &
155 ∃∃T. L.ⓓV1 ⊢ T1 ➤* T & ⇧[0, 1] U2 ≡ T & a = true.
157 elim (cpqs_inv_bind1 … H) -H * /3 width=3/ /3 width=5/
160 lemma cpqs_inv_abst1: ∀a,L,V1,T1,U2. L ⊢ ⓛ{a} V1. T1 ➤* U2 →
161 ∃∃V2,T2. L ⊢ V1 ➤* V2 &
165 elim (cpqs_inv_bind1 … H) -H *
167 | #T #_ #_ #_ #H destruct
171 fact cpqs_inv_flat1_aux: ∀L,U1,U2. L ⊢ U1 ➤* U2 →
172 ∀I,V1,T1. U1 = ⓕ{I} V1. T1 → (
173 ∃∃V2,T2. L ⊢ V1 ➤* V2 & L ⊢ T1 ➤* T2 &
176 (L ⊢ T1 ➤* U2 ∧ I = Cast).
177 #L #U1 #U2 * -L -U1 -U2
178 [ #I #L #J #W1 #U1 #H destruct
179 | #L #K #V #V2 #W2 #i #_ #_ #_ #J #W1 #U1 #H destruct
180 | #a #I #L #V1 #V2 #T1 #T2 #_ #_ #J #W1 #U1 #H destruct
181 | #I #L #V1 #V2 #T1 #T2 #HV12 #HT12 #J #W1 #U1 #H destruct /3 width=5/
182 | #L #V #T1 #T #T2 #_ #_ #J #W1 #U1 #H destruct
183 | #L #V #T1 #T2 #HT12 #J #W1 #U1 #H destruct /3 width=1/
187 lemma cpqs_inv_flat1: ∀I,L,V1,T1,U2. L ⊢ ⓕ{I} V1. T1 ➤* U2 → (
188 ∃∃V2,T2. L ⊢ V1 ➤* V2 & L ⊢ T1 ➤* T2 &
191 (L ⊢ T1 ➤* U2 ∧ I = Cast).
192 /2 width=3 by cpqs_inv_flat1_aux/ qed-.
194 lemma cpqs_inv_appl1: ∀L,V1,T1,U2. L ⊢ ⓐ V1. T1 ➤* U2 →
195 ∃∃V2,T2. L ⊢ V1 ➤* V2 & L ⊢ T1 ➤* T2 &
197 #L #V1 #T1 #U2 #H elim (cpqs_inv_flat1 … H) -H *
203 lemma cpqs_inv_cast1: ∀L,V1,T1,U2. L ⊢ ⓝ V1. T1 ➤* U2 → (
204 ∃∃V2,T2. L ⊢ V1 ➤* V2 & L ⊢ T1 ➤* T2 &
208 #L #V1 #T1 #U2 #H elim (cpqs_inv_flat1 … H) -H * /2 width=1/ /3 width=5/
211 (* Basic forward lemmas *****************************************************)
213 lemma cpqs_fwd_shift1: ∀L1,L,T1,T. L ⊢ L1 @@ T1 ➤* T →
214 ∃∃L2,T2. |L1| = |L2| & T = L2 @@ T2.
215 #L1 @(lenv_ind_dx … L1) -L1 normalize
217 @(ex2_2_intro … (⋆)) // (**) (* explicit constructor *)
218 | #I #L1 #V1 #IH #L #T1 #X
219 >shift_append_assoc normalize #H
220 elim (cpqs_inv_bind1 … H) -H *
221 [ #V0 #T0 #_ #HT10 #H destruct
222 elim (IH … HT10) -IH -HT10 #L2 #T2 #HL12 #H destruct
223 >append_length >HL12 -HL12
224 @(ex2_2_intro … (⋆.ⓑ{I}V0@@L2) T2) [ >append_length ] // /2 width=3/ (**) (* explicit constructor *)
225 | #T #_ #_ #H destruct