1 (**************************************************************************)
4 (* ||A|| A project by Andrea Asperti *)
6 (* ||I|| Developers: *)
7 (* ||T|| The HELM team. *)
8 (* ||A|| http://helm.cs.unibo.it *)
10 (* \ / This file is distributed under the terms of the *)
11 (* v GNU General Public License Version 2 *)
13 (**************************************************************************)
17 let rec move (S: DeqSet) (x:S) (E: pitem S) on E : pre S ≝
21 | ps y ⇒ 〈 `y, false 〉
22 | pp y ⇒ 〈 `y, x == y 〉
23 | po e1 e2 ⇒ (move ? x e1) ⊕ (move ? x e2)
24 | pc e1 e2 ⇒ (move ? x e1) ⊙ (move ? x e2)
25 | pk e ⇒ (move ? x e)^⊛ ].
27 lemma move_plus: ∀S:DeqSet.∀x:S.∀i1,i2:pitem S.
28 move S x (i1 + i2) = (move ? x i1) ⊕ (move ? x i2).
31 lemma move_cat: ∀S:DeqSet.∀x:S.∀i1,i2:pitem S.
32 move S x (i1 · i2) = (move ? x i1) ⊙ (move ? x i2).
35 lemma move_star: ∀S:DeqSet.∀x:S.∀i:pitem S.
36 move S x i^* = (move ? x i)^⊛.
39 lemma fst_eq : ∀A,B.∀a:A.∀b:B. \fst 〈a,b〉 = a.
42 lemma snd_eq : ∀A,B.∀a:A.∀b:B. \snd 〈a,b〉 = b.
45 definition pmove ≝ λS:DeqSet.λx:S.λe:pre S. move ? x (\fst e).
47 lemma pmove_def : ∀S:DeqSet.∀x:S.∀i:pitem S.∀b.
48 pmove ? x 〈i,b〉 = move ? x i.
51 lemma eq_to_eq_hd: ∀A.∀l1,l2:list A.∀a,b.
52 a::l1 = b::l2 → a = b.
53 #A #l1 #l2 #a #b #H destruct //
56 axiom same_kernel: ∀S:DeqSet.∀a:S.∀i:pitem S.
57 |\fst (move ? a i)| = |i|.
60 cases (move S a i1) #i11 #b1 >fst_eq #IH1
61 cases (move S a i2) #i21 #b2 >fst_eq #IH2
64 axiom epsilon_in_star: ∀S.∀A:word S → Prop. A^* [ ].
67 ∀S:DeqSet.∀a:S.∀i:pitem S.∀w: word S.
68 \sem{move ? a i} w ↔ \sem{i} (a::w).
73 |normalize #x #w cases (true_or_false (a==x)) #H >H normalize
74 [>(proj1 … (eqb_true …) H) %
75 [* // #bot @False_ind //| #H1 destruct /2/]
76 |% [#bot @False_ind //
77 | #H1 destruct @(absurd ((a==a)=true))
78 [>(proj2 … (eqb_true …) (refl …)) // | /2/]
81 |#i1 #i2 #HI1 #HI2 #w >(sem_cat S i1 i2) >move_cat
82 @iff_trans[|@sem_odot] >same_kernel >sem_cat_w
83 @iff_trans[||@(iff_or_l … (HI2 w))] @iff_or_r %
84 [* #w1 * #w2 * * #eqw #w1in #w2in @(ex_intro … (a::w1))
85 @(ex_intro … w2) % // % normalize // cases (HI1 w1) /2/
86 |* #w1 * #w2 * cases w1
87 [* #_ #H @False_ind /2/
88 |#x #w3 * #eqaw normalize in eqaw; destruct #w3in #w2in
89 @(ex_intro … w3) @(ex_intro … w2) % // % // cases (HI1 w3) /2/
92 |#i1 #i2 #HI1 #HI2 #w >(sem_plus S i1 i2) >move_plus >sem_plus_w
93 @iff_trans[|@sem_oplus]
94 @iff_trans[|@iff_or_l [|@HI2]| @iff_or_r //]
95 |#i1 #HI1 #w >move_star
96 @iff_trans[|@sem_ostar] >same_kernel >sem_star_w %
97 [* #w1 * #w2 * * #eqw #w1in #w2in
98 @(ex_intro … (a::w1)) @(ex_intro … w2) % // % normalize //
100 |* #w1 * #w2 * cases w1
101 [* #_ #H @False_ind /2/
102 |#x #w3 * #eqaw normalize in eqaw; destruct #w3in #w2in
103 @(ex_intro … w3) @(ex_intro … w2) % // % // cases (HI1 w3) /2/
109 notation > "x ↦* E" non associative with precedence 60 for @{moves ? $x $E}.
110 let rec moves (S : DeqSet) w e on w : pre S ≝
113 | cons x w' ⇒ w' ↦* (move S x (\fst e))].
115 lemma moves_empty: ∀S:DeqSet.∀e:pre S.
119 lemma moves_cons: ∀S:DeqSet.∀a:S.∀w.∀e:pre S.
120 moves ? (a::w) e = moves ? w (move S a (\fst e)).
123 lemma not_epsilon_sem: ∀S:DeqSet.∀a:S.∀w: word S. ∀e:pre S.
124 iff ((a::w) ∈ e) ((a::w) ∈ \fst e).
125 #S #a #w * #i #b >fst_eq cases b normalize
126 [% /2/ * // #H destruct |% normalize /2/]
129 lemma same_kernel_moves: ∀S:DeqSet.∀w.∀e:pre S.
130 |\fst (moves ? w e)| = |\fst e|.
134 theorem decidable_sem: ∀S:DeqSet.∀w: word S. ∀e:pre S.
135 (\snd (moves ? w e) = true) ↔ \sem{e} w.
137 [* #i #b >moves_empty cases b % /2/
138 |#a #w1 #Hind #e >moves_cons
139 @iff_trans [||@iff_sym @not_epsilon_sem]
140 @iff_trans [||@move_ok] @Hind
144 lemma not_true_to_false: ∀b.b≠true → b =false.
145 #b * cases b // #H @False_ind /2/
148 theorem equiv_sem: ∀S:DeqSet.∀e1,e2:pre S.
149 iff (\sem{e1} =1 \sem{e2}) (∀w.\snd (moves ? w e1) = \snd (moves ? w e2)).
152 cut (∀b1,b2. iff (b1 = true) (b2 = true) → (b1 = b2))
153 [* * // * #H1 #H2 [@sym_eq @H1 //| @H2 //]]
154 #Hcut @Hcut @iff_trans [|@decidable_sem]
155 @iff_trans [|@same_sem] @iff_sym @decidable_sem
156 |#H #w1 @iff_trans [||@decidable_sem] <H @iff_sym @decidable_sem]
159 axiom moves_left : ∀S,a,w,e.
160 moves S (w@[a]) e = move S a (\fst (moves S w e)).
162 definition in_moves ≝ λS:DeqSet.λw.λe:pre S. \snd(w ↦* e).
164 coinductive equiv (S:DeqSet) : pre S → pre S → Prop ≝
168 (∀x. equiv S (move ? x (\fst e1)) (move ? x (\fst e2))) →
171 definition beqb ≝ λb1,b2.
177 lemma beqb_ok: ∀b1,b2. iff (beqb b1 b2 = true) (b1 = b2).
178 #b1 #b2 cases b1 cases b2 normalize /2/
181 definition Bin ≝ mk_DeqSet bool beqb beqb_ok.
183 let rec beqitem S (i1,i2: pitem S) on i1 ≝
185 [ pz ⇒ match i2 with [ pz ⇒ true | _ ⇒ false]
186 | pe ⇒ match i2 with [ pe ⇒ true | _ ⇒ false]
187 | ps y1 ⇒ match i2 with [ ps y2 ⇒ y1==y2 | _ ⇒ false]
188 | pp y1 ⇒ match i2 with [ pp y2 ⇒ y1==y2 | _ ⇒ false]
189 | po i11 i12 ⇒ match i2 with
190 [ po i21 i22 ⇒ beqitem S i11 i21 ∧ beqitem S i12 i22
192 | pc i11 i12 ⇒ match i2 with
193 [ pc i21 i22 ⇒ beqitem S i11 i21 ∧ beqitem S i12 i22
195 | pk i11 ⇒ match i2 with [ pk i21 ⇒ beqitem S i11 i21 | _ ⇒ false]
198 axiom beqitem_ok: ∀S,i1,i2. iff (beqitem S i1 i2 = true) (i1 = i2).
201 mk_DeqSet (pitem Bin) (beqitem Bin) (beqitem_ok Bin).
203 definition beqpre ≝ λS:DeqSet.λe1,e2:pre S.
204 beqitem S (\fst e1) (\fst e2) ∧ beqb (\snd e1) (\snd e2).
206 definition beqpairs ≝ λS:DeqSet.λp1,p2:(pre S)×(pre S).
207 beqpre S (\fst p1) (\fst p2) ∧ beqpre S (\snd p1) (\snd p2).
209 axiom beqpairs_ok: ∀S,p1,p2. iff (beqpairs S p1 p2 = true) (p1 = p2).
211 definition space ≝ λS.mk_DeqSet ((pre S)×(pre S)) (beqpairs S) (beqpairs_ok S).
213 definition sons ≝ λp:space Bin.
214 [〈move Bin true (\fst (\fst p)), move Bin true (\fst (\snd p))〉;
215 〈move Bin false (\fst (\fst p)), move Bin false (\fst (\snd p))〉
218 axiom memb_sons: ∀p,q. memb (space Bin) p (sons q) = true →
219 ∃a.(move ? a (\fst (\fst q)) = \fst p ∧
220 move ? a (\fst (\snd q)) = \snd p).
223 let rec test_sons (l:list (space Bin)) ≝
227 beqb (\snd (\fst hd)) (\snd (\snd hd)) ∧ test_sons tl
230 let rec bisim (n:nat) (frontier,visited: list (space Bin)) ≝
232 [ O ⇒ 〈false,visited〉 (* assert false *)
235 [ nil ⇒ 〈true,visited〉
237 if beqb (\snd (\fst hd)) (\snd (\snd hd)) then
238 bisim m (unique_append ? (filter ? (λx.notb (memb ? x (hd::visited)))
239 (sons hd)) tl) (hd::visited)
244 lemma unfold_bisim: ∀n.∀frontier,visited: list (space Bin).
245 bisim n frontier visited =
247 [ O ⇒ 〈false,visited〉 (* assert false *)
250 [ nil ⇒ 〈true,visited〉
252 if beqb (\snd (\fst hd)) (\snd (\snd hd)) then
253 bisim m (unique_append ? (filter ? (λx.notb(memb ? x (hd::visited))) (sons hd)) tl) (hd::visited)
259 lemma bisim_never: ∀frontier,visited: list (space Bin).
260 bisim O frontier visited = 〈false,visited〉.
261 #frontier #visited >unfold_bisim //
264 lemma bisim_end: ∀m.∀visited: list (space Bin).
265 bisim (S m) [] visited = 〈true,visited〉.
266 #n #visisted >unfold_bisim //
269 lemma bisim_step_true: ∀m.∀p.∀frontier,visited: list (space Bin).
270 beqb (\snd (\fst p)) (\snd (\snd p)) = true →
271 bisim (S m) (p::frontier) visited =
272 bisim m (unique_append ? (filter ? (λx.notb(memb (space Bin) x (p::visited))) (sons p)) frontier) (p::visited).
273 #m #p #frontier #visited #test >unfold_bisim normalize nodelta >test //
276 lemma bisim_step_false: ∀m.∀p.∀frontier,visited: list (space Bin).
277 beqb (\snd (\fst p)) (\snd (\snd p)) = false →
278 bisim (S m) (p::frontier) visited = 〈false,visited〉.
279 #m #p #frontier #visited #test >unfold_bisim normalize nodelta >test //
282 definition visited_inv ≝ λe1,e2:pre Bin.λvisited: list (space Bin).
283 uniqueb ? visited = true ∧
284 ∀p. memb ? p visited = true →
285 (∃w.(moves Bin w e1 = \fst p) ∧ (moves Bin w e2 = \snd p)) ∧
286 (beqb (\snd (\fst p)) (\snd (\snd p)) = true).
288 definition frontier_inv ≝ λfrontier,visited: list (space Bin).
289 uniqueb ? frontier = true ∧
290 ∀p. memb ? p frontier = true →
291 memb ? p visited = false ∧
292 ∃p1.((memb ? p1 visited = true) ∧
293 (∃a. move ? a (\fst (\fst p1)) = \fst p ∧
294 move ? a (\fst (\snd p1)) = \snd p)).
296 (* lemma andb_true: ∀b1,b2:bool.
297 (b1 ∧ b2) = true → (b1 = true) ∧ (b2 = true).
298 #b1 #b2 cases b1 normalize #H [>H /2/ |@False_ind /2/].
301 lemma andb_true_r: ∀b1,b2:bool.
302 (b1 = true) ∧ (b2 = true) → (b1 ∧ b2) = true.
303 #b1 #b2 cases b1 normalize * //
306 lemma notb_eq_true_l: ∀b. notb b = true → b = false.
307 #b cases b normalize //
310 lemma notb_eq_true_r: ∀b. b = false → notb b = true.
311 #b cases b normalize //
314 lemma notb_eq_false_l:∀b. notb b = false → b = true.
315 #b cases b normalize //
318 lemma notb_eq_false_r:∀b. b = true → notb b = false.
319 #b cases b normalize //
323 include "arithmetics/exp.ma".
325 let rec pos S (i:re S) on i ≝
330 | o i1 i2 ⇒ pos S i1 + pos S i2
331 | c i1 i2 ⇒ pos S i1 + pos S i2
336 let rec pitem_enum S (i:re S) on i ≝
340 | s y ⇒ [ps S y; pp S y]
341 | o i1 i2 ⇒ compose ??? (po S) (pitem_enum S i1) (pitem_enum S i2)
342 | c i1 i2 ⇒ compose ??? (pc S) (pitem_enum S i1) (pitem_enum S i2)
343 | k i ⇒ map ?? (pk S) (pitem_enum S i)
346 axiom pitem_enum_complete: ∀i: pitem Bin.
347 memb BinItem i (pitem_enum ? (forget ? i)) = true.
354 |#i1 #i2 #Hind1 #Hind2 @memb_compose //
355 |#i1 #i2 #Hind1 #Hind2 @memb_compose //
359 definition pre_enum ≝ λS.λi:re S.
360 compose ??? (λi,b.〈i,b〉) (pitem_enum S i) [true;false].
362 definition space_enum ≝ λS.λi1,i2:re S.
363 compose ??? (λe1,e2.〈e1,e2〉) (pre_enum S i1) (pre_enum S i1).
365 axiom space_enum_complete : ∀S.∀e1,e2: pre S.
366 memb (space S) 〈e1,e2〉 (space_enum S (|\fst e1|) (|\fst e2|)) = true.
368 lemma bisim_ok1: ∀e1,e2:pre Bin.\sem{e1}=1\sem{e2} →
369 ∀n.∀frontier,visited:list (space Bin).
370 |space_enum Bin (|\fst e1|) (|\fst e2|)| < n + |visited|→
371 visited_inv e1 e2 visited → frontier_inv frontier visited →
372 \fst (bisim n frontier visited) = true.
373 #e1 #e2 #same #n elim n
374 [#frontier #visited #abs * #unique #H @False_ind @(absurd … abs)
375 @le_to_not_lt @sublist_length // * #e11 #e21 #membp
376 cut ((|\fst e11| = |\fst e1|) ∧ (|\fst e21| = |\fst e2|))
377 [|* #H1 #H2 <H1 <H2 @space_enum_complete]
378 cases (H … membp) * #w * >fst_eq >snd_eq #we1 #we2 #_
380 |#m #HI * [#visited #vinv #finv >bisim_end //]
381 #p #front_tl #visited #Hn * #u_visited #vinv * #u_frontier #finv
382 cases (finv p (memb_hd …)) #Hp * #p2 * #visited_p2
383 * #a * #movea1 #movea2
384 cut (∃w.(moves Bin w e1 = \fst p) ∧ (moves Bin w e2 = \snd p))
385 [cases (vinv … visited_p2) -vinv * #w1 * #mw1 #mw2 #_
386 @(ex_intro … (w1@[a])) /2/]
387 -movea2 -movea1 -a -visited_p2 -p2 #reachp
388 cut (beqb (\snd (\fst p)) (\snd (\snd p)) = true)
389 [cases reachp #w * #move_e1 #move_e2 <move_e1 <move_e2
390 @(proj2 … (beqb_ok … )) @(proj1 … (equiv_sem … )) @same
391 |#ptest >(bisim_step_true … ptest) @HI -HI
393 |% [@andb_true_r % [@notb_eq_false_l // | // ]]
394 #p1 #H (cases (orb_true_l … H))
395 [#eqp <(proj1 … (eqb_true (space Bin) ? p1) eqp) % //
396 |#visited_p1 @(vinv … visited_p1)
398 |whd % [@unique_append_unique @(andb_true_r … u_frontier)]
399 @unique_append_elim #q #H
401 [@notb_eq_true_l @(filter_true … H)
402 |@(ex_intro … p) % //
403 @(memb_sons … (memb_filter_memb … H))
405 |cases (finv q ?) [|@memb_cons //]
406 #nvq * #p1 * #Hp1 #reach %
407 [cut ((p==q) = false) [|#Hpq whd in ⊢ (??%?); >Hpq @nvq]
408 cases (andb_true_l … u_frontier) #notp #_
409 @(not_memb_to_not_eq … H) @notb_eq_true_l @notp
410 |cases (proj2 … (finv q ?))
411 [#p1 * #Hp1 #reach @(ex_intro … p1) % // @memb_cons //
421 definition all_true ≝ λl.∀p. memb (space Bin) p l = true →
422 (beqb (\snd (\fst p)) (\snd (\snd p)) = true).
424 definition sub_sons ≝ λl1,l2.∀x,a.
425 memb (space Bin) x l1 = true →
426 memb (space Bin) 〈move ? a (\fst (\fst x)), move ? a (\fst (\snd x))〉 l2 = true.
428 lemma reachable_bisim:
429 ∀n.∀frontier,visited,visited_res:list (space Bin).
431 sub_sons visited (frontier@visited) →
432 bisim n frontier visited = 〈true,visited_res〉 →
433 (sub_sons visited_res visited_res ∧
434 sublist ? visited visited_res ∧
435 all_true visited_res).
437 [#fron #vis #vis_res #_ #_ >bisim_never #H destruct
439 [-Hind #vis #vis_res #allv #H normalize in ⊢ (%→?);
440 #H1 destruct % // % // #p /2/
441 |#hd cases (true_or_false (beqb (\snd (\fst hd)) (\snd (\snd hd))))
442 [|#H #tl #vis #vis_res #allv >(bisim_step_false … H) #_ #H1 destruct]
443 #H #tl #visited #visited_res #allv >(bisim_step_true … H)
444 cut (all_true (hd::visited))
445 [#p #H cases (orb_true_l … H)
446 [#eqp <(proj1 … (eqb_true …) eqp) // |@allv]]
447 #allh #subH #bisim cases (Hind … allh … bisim) -Hind
448 [* #H1 #H2 #H3 % // % // #p #H4 @H2 @memb_cons //]
450 cases (orb_true_l … membx)
451 [#eqhdx >(proj1 … (eqb_true …) eqhdx)
452 letin xa ≝ 〈move Bin a (\fst (\fst x)), move Bin a (\fst (\snd x))〉
453 cases (true_or_false … (memb (space Bin) xa (x::visited)))
454 [#membxa @memb_append_l2 //
455 |#membxa @memb_append_l1 @sublist_unique_append_l1 @memb_filter_l
456 [whd in ⊢ (??(??%%)?); cases a [@memb_hd |@memb_cons @memb_hd]
460 |#H1 letin xa ≝ 〈move Bin a (\fst (\fst x)), move Bin a (\fst (\snd x))〉
461 cases (memb_append … (subH x a H1))
462 [#H2 (cases (orb_true_l … H2))
463 [#H3 @memb_append_l2 >(proj1 … (eqb_true …) H3) @memb_hd
464 |#H3 @memb_append_l1 @sublist_unique_append_l2 @H3
466 |#H2 @memb_append_l2 @memb_cons @H2
473 axiom bisim_char: ∀e1,e2:pre Bin.
474 (∀w.(beqb (\snd (moves ? w e1)) (\snd (moves ? w e2))) = true) →
477 lemma bisim_ok2: ∀e1,e2:pre Bin.
478 (beqb (\snd e1) (\snd e2) = true) →
479 ∀n.∀frontier:list (space Bin).
480 sub_sons [〈e1,e2〉] (frontier@[〈e1,e2〉]) →
481 \fst (bisim n frontier [〈e1,e2〉]) = true → \sem{e1}=1\sem{e2}.
482 #e1 #e2 #Hnil #n #frontier #init #bisim_true
483 letin visited_res ≝ (\snd (bisim n frontier [〈e1,e2〉]))
484 cut (bisim n frontier [〈e1,e2〉] = 〈true,visited_res〉)
485 [<bisim_true <eq_pair_fst_snd //] #H
486 cut (all_true [〈e1,e2〉])
487 [#p #Hp cases (orb_true_l … Hp)
488 [#eqp <(proj1 … (eqb_true …) eqp) //
489 | whd in ⊢ ((??%?)→?); #abs @False_ind /2/
491 cases (reachable_bisim … allH init … H) * #H1 #H2 #H3
492 cut (∀w,p.memb (space Bin) p visited_res = true →
493 memb (space Bin) 〈moves ? w (\fst p), moves ? w (\snd p)〉 visited_res = true)
495 #a #w1 #Hind * #e11 #e21 #visp >fst_eq >snd_eq >moves_cons >moves_cons
496 @(Hind 〈?,?〉) @(H1 〈?,?〉) //] #all_reach
497 @bisim_char #w @(H3 〈?,?〉) @(all_reach w 〈?,?〉) @H2 //
500 definition tt ≝ ps Bin true.
501 definition ff ≝ ps Bin false.
502 definition eps ≝ pe Bin.
503 definition exp1 ≝ (ff + tt · ff).
504 definition exp2 ≝ ff · (eps + tt).
506 definition exp3 ≝ move Bin true (\fst (•exp1)).
507 definition exp4 ≝ move Bin true (\fst (•exp2)).
508 definition exp5 ≝ move Bin false (\fst (•exp1)).
509 definition exp6 ≝ move Bin false (\fst (•exp2)).
511 example comp1 : bequiv 15 (•exp1) (•exp2) [ ] = false .