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4 (* ||A|| A project by Andrea Asperti *)
6 (* ||I|| Developers: *)
7 (* ||T|| The HELM team. *)
8 (* ||A|| http://helm.tcs.unibo.it *)
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15 include "ground_2/notation/functions/apply_2.ma".
16 include "ground_2/notation/relations/rat_3.ma".
17 include "ground_2/relocation/nstream.ma".
19 (* RELOCATION N-STREAM ******************************************************)
21 let rec apply (i: nat) on i: nstream → nat ≝ ?.
24 | #i lapply (apply i t) -apply -i -t
29 interpretation "functional application (nstream)"
30 'Apply t i = (apply i t).
32 inductive at: nstream → relation nat ≝
33 | at_zero: ∀t. at (0 @ t) 0 0
34 | at_skip: ∀t,i1,i2. at t i1 i2 → at (0 @ t) (⫯i1) (⫯i2)
35 | at_lift: ∀t,b,i1,i2. at (b @ t) i1 i2 → at (⫯b @ t) i1 (⫯i2)
38 interpretation "relational application (nstream)"
39 'RAt i1 t i2 = (at t i1 i2).
41 (* Basic properties on apply ************************************************)
43 lemma apply_S1: ∀t,a,i. (⫯a@t)@❴i❵ = ⫯((a@t)@❴i❵).
47 (* Basic inversion lemmas on at *********************************************)
49 fact at_inv_xOx_aux: ∀t,i1,i2. @⦃i1, t⦄ ≡ i2 → ∀u. t = 0 @ u →
51 ∃∃j1,j2. @⦃j1, u⦄ ≡ j2 & i1 = ⫯j1 & i2 = ⫯j2.
52 #t #i1 #i2 * -t -i1 -i2
53 [ /3 width=1 by or_introl, conj/
54 | #t #i1 #i2 #Hi #u #H destruct /3 width=5 by ex3_2_intro, or_intror/
55 | #t #b #i1 #i2 #_ #u #H destruct
59 lemma at_inv_xOx: ∀t,i1,i2. @⦃i1, 0 @ t⦄ ≡ i2 →
61 ∃∃j1,j2. @⦃j1, t⦄ ≡ j2 & i1 = ⫯j1 & i2 = ⫯j2.
62 /2 width=3 by at_inv_xOx_aux/ qed-.
64 lemma at_inv_OOx: ∀t,i. @⦃0, 0 @ t⦄ ≡ i → i = 0.
65 #t #i #H elim (at_inv_xOx … H) -H * //
66 #j1 #j2 #_ #H destruct
69 lemma at_inv_xOO: ∀t,i. @⦃i, 0 @ t⦄ ≡ 0 → i = 0.
70 #t #i #H elim (at_inv_xOx … H) -H * //
71 #j1 #j2 #_ #_ #H destruct
74 lemma at_inv_SOx: ∀t,i1,i2. @⦃⫯i1, 0 @ t⦄ ≡ i2 →
75 ∃∃j2. @⦃i1, t⦄ ≡ j2 & i2 = ⫯j2.
76 #t #i1 #i2 #H elim (at_inv_xOx … H) -H *
78 | #j1 #j2 #Hj #H1 #H2 destruct /2 width=3 by ex2_intro/
82 lemma at_inv_xOS: ∀t,i1,i2. @⦃i1, 0 @ t⦄ ≡ ⫯i2 →
83 ∃∃j1. @⦃j1, t⦄ ≡ i2 & i1 = ⫯j1.
84 #t #i1 #i2 #H elim (at_inv_xOx … H) -H *
86 | #j1 #j2 #Hj #H1 #H2 destruct /2 width=3 by ex2_intro/
90 lemma at_inv_SOS: ∀t,i1,i2. @⦃⫯i1, 0 @ t⦄ ≡ ⫯i2 → @⦃i1, t⦄ ≡ i2.
91 #t #i1 #i2 #H elim (at_inv_xOx … H) -H *
93 | #j1 #j2 #Hj #H1 #H2 destruct //
97 lemma at_inv_OOS: ∀t,i. @⦃0, 0 @ t⦄ ≡ ⫯i → ⊥.
98 #t #i #H elim (at_inv_xOx … H) -H *
100 | #j1 #j2 #_ #H destruct
104 lemma at_inv_SOO: ∀t,i. @⦃⫯i, 0 @ t⦄ ≡ 0 → ⊥.
105 #t #i #H elim (at_inv_xOx … H) -H *
107 | #j1 #j2 #_ #_ #H destruct
111 fact at_inv_xSx_aux: ∀t,i1,i2. @⦃i1, t⦄ ≡ i2 → ∀u,a. t = ⫯a @ u →
112 ∃∃j2. @⦃i1, a@u⦄ ≡ j2 & i2 = ⫯j2.
113 #t #i1 #i2 * -t -i1 -i2
114 [ #t #u #a #H destruct
115 | #t #i1 #i2 #_ #u #a #H destruct
116 | #t #b #i1 #i2 #Hi #u #a #H destruct /2 width=3 by ex2_intro/
120 lemma at_inv_xSx: ∀t,b,i1,i2. @⦃i1, ⫯b @ t⦄ ≡ i2 →
121 ∃∃j2. @⦃i1, b @ t⦄ ≡ j2 & i2 = ⫯j2.
122 /2 width=3 by at_inv_xSx_aux/ qed-.
124 lemma at_inv_xSS: ∀t,b,i1,i2. @⦃i1, ⫯b @ t⦄ ≡ ⫯i2 → @⦃i1, b@t⦄ ≡ i2.
125 #t #b #i1 #i2 #H elim (at_inv_xSx … H) -H
126 #j2 #Hj #H destruct //
129 lemma at_inv_xSO: ∀t,b,i. @⦃i, ⫯b @ t⦄ ≡ 0 → ⊥.
130 #t #b #i #H elim (at_inv_xSx … H) -H
134 (* alternative definition ***************************************************)
136 lemma at_O1: ∀b,t. @⦃0, b @ t⦄ ≡ b.
137 #b elim b -b /2 width=1 by at_lift/
140 lemma at_S1: ∀b,t,i1,i2. @⦃i1, t⦄ ≡ i2 → @⦃⫯i1, b@t⦄ ≡ ⫯(b+i2).
141 #b elim b -b /3 width=1 by at_skip, at_lift/
144 lemma at_inv_O1: ∀t,b,i2. @⦃0, b@t⦄ ≡ i2 → i2 = b.
145 #t #b elim b -b /2 width=2 by at_inv_OOx/
146 #b #IH #i2 #H elim (at_inv_xSx … H) -H
147 #j2 #Hj #H destruct /3 width=1 by eq_f/
150 lemma at_inv_S1: ∀t,b,j1,i2. @⦃⫯j1, b@t⦄ ≡ i2 → ∃∃j2. @⦃j1, t⦄ ≡ j2 & i2 =⫯(b+j2).
151 #t #b elim b -b /2 width=1 by at_inv_SOx/
152 #b #IH #j1 #i2 #H elim (at_inv_xSx … H) -H
153 #j2 #Hj #H destruct elim (IH … Hj) -IH -Hj
154 #i2 #Hi #H destruct /2 width=3 by ex2_intro/
157 lemma at_total: ∀i,t. @⦃i, t⦄ ≡ t@❴i❵.
159 [ * // | #i #IH * /3 width=1 by at_S1/ ]
162 (* Advanced forward lemmas on at ********************************************)
164 lemma at_increasing: ∀t,i1,i2. @⦃i1, t⦄ ≡ i2 → i1 ≤ i2.
165 #t #i1 #i2 #H elim H -t -i1 -i2 /2 width=1 by le_S_S, le_S/
168 lemma at_increasing_plus: ∀t,b,i1,i2. @⦃i1, b@t⦄ ≡ i2 → i1 + b ≤ i2.
170 [ #i2 #H >(at_inv_O1 … H) -i2 //
171 | #i1 #i2 #H elim (at_inv_S1 … H) -H
173 /4 width=2 by at_increasing, monotonic_le_plus_r, le_S_S/
177 lemma at_increasing_strict: ∀t,b,i1,i2. @⦃i1, ⫯b @ t⦄ ≡ i2 →
178 i1 < i2 ∧ @⦃i1, b@t⦄ ≡ ⫰i2.
179 #t #b #i1 #i2 #H elim (at_inv_xSx … H) -H
180 #j2 #Hj #H destruct /4 width=2 by conj, at_increasing, le_S_S/
183 (* Main properties on at ****************************************************)
185 let corec at_ext: ∀t1,t2. (∀i,i1,i2. @⦃i, t1⦄ ≡ i1 → @⦃i, t2⦄ ≡ i2 → i1 = i2) → t1 ≐ t2 ≝ ?.
186 * #b1 #t1 * #b2 #t2 #Hi lapply (Hi 0 b1 b2 ? ?) //
187 #H lapply (at_ext t1 t2 ?) /2 width=1 by eq_sec/ -at_ext
188 #j #j1 #j2 #H1 #H2 @(injective_plus_r … b2) /4 width=5 by at_S1, injective_S/ (**) (* full auto fails *)
191 theorem at_monotonic: ∀i1,i2. i1 < i2 → ∀t,j1,j2. @⦃i1, t⦄ ≡ j1 → @⦃i2, t⦄ ≡ j2 → j1 < j2.
192 #i1 #i2 #H @(lt_elim … H) -i1 -i2
193 [ #i2 *#b #t #j1 #j2 #H1 #H2 >(at_inv_O1 … H1) elim (at_inv_S1 … H2) -H2 -j1 //
194 | #i1 #i2 #IH * #b #t #j1 #j2 #H1 #H2 elim (at_inv_S1 … H2) elim (at_inv_S1 … H1) -H1 -H2
195 #x1 #Hx1 #H1 #x2 #Hx2 #H2 destruct /4 width=3 by lt_S_S, monotonic_lt_plus_r/
199 theorem at_inv_monotonic: ∀t,i1,j1. @⦃i1, t⦄ ≡ j1 → ∀i2,j2. @⦃i2, t⦄ ≡ j2 → j2 < j1 → i2 < i1.
200 #t #i1 #j1 #H elim H -t -i1 -j1
201 [ #t #i2 #j2 #_ #H elim (lt_le_false … H) //
202 | #t #i1 #j1 #_ #IH #i2 #j2 #H #Hj elim (at_inv_xOx … H) -H *
203 [ #H1 #H2 destruct //
204 | #x2 #y2 #Hxy #H1 #H2 destruct /4 width=3 by lt_S_S_to_lt, lt_S_S/
206 | #t #b1 #i1 #j1 #_ #IH #i2 #j2 #H #Hj elim (at_inv_xSx … H) -H
207 #y2 #Hy #H destruct /3 width=3 by lt_S_S_to_lt/
211 theorem at_mono: ∀t,i,i1. @⦃i, t⦄ ≡ i1 → ∀i2. @⦃i, t⦄ ≡ i2 → i2 = i1.
212 #t #i #i1 #H1 #i2 #H2 elim (lt_or_eq_or_gt i2 i1) //
213 #Hi elim (lt_le_false i i) /2 width=6 by at_inv_monotonic/
216 theorem at_inj: ∀t,i1,i. @⦃i1, t⦄ ≡ i → ∀i2. @⦃i2, t⦄ ≡ i → i1 = i2.
217 #t #i1 #i #H1 #i2 #H2 elim (lt_or_eq_or_gt i2 i1) //
218 #Hi elim (lt_le_false i i) /2 width=6 by at_monotonic/
221 (* Advanced properties on at ************************************************)
223 (* Note: see also: trace_at/at_dec *)
224 lemma at_dec: ∀t,i1,i2. Decidable (@⦃i1, t⦄ ≡ i2).
225 #t #i1 #i2 lapply (at_total i1 t)
226 #Ht elim (eq_nat_dec i2 (t@❴i1❵))
227 [ #H destruct /2 width=1 by or_introl/
228 | /4 width=4 by at_mono, or_intror/
232 lemma is_at_dec_le: ∀t,i2,i. (∀i1. i1 + i ≤ i2 → @⦃i1, t⦄ ≡ i2 → ⊥) → Decidable (∃i1. @⦃i1, t⦄ ≡ i2).
234 [ #Ht @or_intror * /3 width=3 by at_increasing/
235 | #i #IH #Ht elim (at_dec t (i2-i) i2) /3 width=2 by ex_intro, or_introl/
236 #Hi2 @IH -IH #i1 #H #Hi elim (le_to_or_lt_eq … H) -H /2 width=3 by/
237 #H destruct -Ht /2 width=1 by/
241 (* Note: see also: trace_at/is_at_dec *)
242 lemma is_at_dec: ∀t,i2. Decidable (∃i1. @⦃i1, t⦄ ≡ i2).
243 #t #i2 @(is_at_dec_le ? ? (⫯i2)) /2 width=4 by lt_le_false/