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.
8 \ / This file is distributed under the terms of the
9 \ / GNU General Public License Version 2
10 V_____________________________________________________________*)
12 include "basics/vectors.ma".
13 (* include "basics/relations.ma". *)
16 record tape (sig:FinSet): Type[0] ≝
17 { left : list (option sig);
18 right: list (option sig)
22 inductive tape (sig:FinSet) : Type[0] ≝
24 | leftof : sig → list sig → tape sig
25 | rightof : sig → list sig → tape sig
26 | midtape : list sig → sig → list sig → tape sig.
29 λsig.λt:tape sig.match t with
33 | midtape l _ _ ⇒ l ].
36 λsig.λt:tape sig.match t with
40 | midtape _ _ r ⇒ r ].
44 λsig.λt:tape sig.match t with
45 [ midtape _ c _ ⇒ Some ? c
49 ∀sig:FinSet.list sig → option sig → list sig → tape sig ≝
50 λsig,lt,c,rt.match c with
51 [ Some c' ⇒ midtape sig lt c' rt
52 | None ⇒ match lt with
55 | cons r0 rs0 ⇒ leftof ? r0 rs0 ]
56 | cons l0 ls0 ⇒ rightof ? l0 ls0 ] ].
58 inductive move : Type[0] ≝
64 (* We do not distinuish an input tape *)
66 record TM (sig:FinSet): Type[1] ≝
68 trans : states × (option sig) → states × (option (sig × move));
73 record config (sig,states:FinSet): Type[0] ≝
78 (* definition option_hd ≝ λA.λl:list (option A).
85 (*definition tape_write ≝ λsig.λt:tape sig.λs:sig.
86 <left ? t) s (right ? t).
88 | Some s' ⇒ midtape ? (left ? t) s' (right ? t) ].*)
90 definition tape_move_left ≝ λsig:FinSet.λlt:list sig.λc:sig.λrt:list sig.
92 [ nil ⇒ leftof sig c rt
93 | cons c0 lt0 ⇒ midtape sig lt0 c0 (c::rt) ].
95 definition tape_move_right ≝ λsig:FinSet.λlt:list sig.λc:sig.λrt:list sig.
97 [ nil ⇒ rightof sig c lt
98 | cons c0 rt0 ⇒ midtape sig (c::lt) c0 rt0 ].
100 definition tape_move ≝ λsig.λt: tape sig.λm:option (sig × move).
106 [ R ⇒ tape_move_right ? (left ? t) s (right ? t)
107 | L ⇒ tape_move_left ? (left ? t) s (right ? t)
108 | N ⇒ midtape ? (left ? t) s (right ? t)
113 (None,a::b::rs) → None::b::rs
114 (Some a,[]) → [Some a]
115 (Some a,b::rs) → Some a::rs
118 definition option_cons ≝ λA.λa:option A.λl.
120 [ None ⇒ match l with
125 (* definition tape_update := λsig.λt: tape sig.λs:option sig.
130 | Some a ⇒ [Some ? a] ]
131 | cons b rs ⇒ match s with
132 [ None ⇒ match rs with
134 | cons _ _ ⇒ None ?::rs ]
135 | Some a ⇒ Some ? a::rs ] ]
136 in mk_tape ? (left ? t) newright. *)
138 definition tape_move ≝ λsig.λt:tape sig.λm:option sig × move.
139 let 〈s,m1〉 ≝ m in match m1 with
140 [ R ⇒ mk_tape sig (option_cons ? s (left ? t)) (tail ? (right ? t))
141 | L ⇒ mk_tape sig (tail ? (left ? t))
142 (option_cons ? (option_hd ? (left ? t))
143 (option_cons ? s (tail ? (right ? t))))
144 | N ⇒ mk_tape sig (left ? t) (option_cons ? s (tail ? (right ? t)))
148 definition step ≝ λsig.λM:TM sig.λc:config sig (states sig M).
149 let current_char ≝ current ? (ctape ?? c) in
150 let 〈news,mv〉 ≝ trans sig M 〈cstate ?? c,current_char〉 in
151 mk_config ?? news (tape_move sig (ctape ?? c) mv).
153 let rec loop (A:Type[0]) n (f:A→A) p a on n ≝
156 | S m ⇒ if p a then (Some ? a) else loop A m f p (f a)
159 lemma loop_incr : ∀A,f,p,k1,k2,a1,a2.
160 loop A k1 f p a1 = Some ? a2 →
161 loop A (k2+k1) f p a1 = Some ? a2.
162 #A #f #p #k1 #k2 #a1 #a2 generalize in match a1; elim k1
163 [normalize #a0 #Hfalse destruct
164 |#k1' #IH #a0 <plus_n_Sm whd in ⊢ (??%? → ??%?);
165 cases (true_or_false (p a0)) #Hpa0 >Hpa0 whd in ⊢ (??%? → ??%?); // @IH
169 lemma loop_merge : ∀A,f,p,q.(∀b. p b = false → q b = false) →
171 loop A k1 f p a1 = Some ? a2 →
172 f a2 = a3 → q a2 = false →
173 loop A k2 f q a3 = Some ? a4 →
174 loop A (k1+k2) f q a1 = Some ? a4.
175 #Sig #f #p #q #Hpq #k1 elim k1
176 [normalize #k2 #a1 #a2 #a3 #a4 #H destruct
177 |#k1' #Hind #k2 #a1 #a2 #a3 #a4 normalize in ⊢ (%→?);
178 cases (true_or_false (p a1)) #pa1 >pa1 normalize in ⊢ (%→?);
179 [#eqa1a2 destruct #eqa2a3 #Hqa2 #H
180 whd in ⊢ (??(??%???)?); >plus_n_Sm @loop_incr
181 whd in ⊢ (??%?); >Hqa2 >eqa2a3 @H
182 |normalize >(Hpq … pa1) normalize
183 #H1 #H2 #H3 @(Hind … H2) //
188 lemma loop_split : ∀A,f,p,q.(∀b. q b = true → p b = true) →
190 loop A k f q a1 = Some ? a2 →
192 loop A k1 f p a1 = Some ? a3 ∧
193 loop A (S(k-k1)) f q a3 = Some ? a2.
194 #A #f #p #q #Hpq #k elim k
195 [#a1 #a2 normalize #Heq destruct
196 |#i #Hind #a1 #a2 normalize
197 cases (true_or_false (q a1)) #Hqa1 >Hqa1 normalize
199 @(ex_intro … 1) @(ex_intro … a2) %
200 [normalize >(Hpq …Hqa1) // |>Hqa1 //]
201 |#Hloop cases (true_or_false (p a1)) #Hpa1
202 [@(ex_intro … 1) @(ex_intro … a1) %
203 [normalize >Hpa1 // |>Hqa1 <Hloop normalize //]
204 |cases (Hind …Hloop) #k2 * #a3 * #Hloop1 #Hloop2
205 @(ex_intro … (S k2)) @(ex_intro … a3) %
206 [normalize >Hpa1 normalize // | @Hloop2 ]
213 lemma loop_split : ∀A,f,p,q.(∀b. p b = false → q b = false) →
215 loop A k1 f p a1 = Some ? a2 →
216 loop A k2 f q a2 = Some ? a3 →
217 loop A (k1+k2) f q a1 = Some ? a3.
218 #Sig #f #p #q #Hpq #k1 elim k1
219 [normalize #k2 #a1 #a2 #a3 #H destruct
220 |#k1' #Hind #k2 #a1 #a2 #a3 normalize in ⊢ (%→?→?);
221 cases (true_or_false (p a1)) #pa1 >pa1 normalize in ⊢ (%→?);
222 [#eqa1a2 destruct #H @loop_incr //
223 |normalize >(Hpq … pa1) normalize
224 #H1 #H2 @(Hind … H2) //
230 definition initc ≝ λsig.λM:TM sig.λt.
231 mk_config sig (states sig M) (start sig M) t.
233 definition Realize ≝ λsig.λM:TM sig.λR:relation (tape sig).
235 loop ? i (step sig M) (λc.halt sig M (cstate ?? c)) (initc sig M t) = Some ? outc ∧
238 definition WRealize ≝ λsig.λM:TM sig.λR:relation (tape sig).
240 loop ? i (step sig M) (λc.halt sig M (cstate ?? c)) (initc sig M t) = Some ? outc →
243 definition Terminate ≝ λsig.λM:TM sig.λt. ∃i,outc.
244 loop ? i (step sig M) (λc.halt sig M (cstate ?? c)) (initc sig M t) = Some ? outc.
246 lemma WRealize_to_Realize : ∀sig.∀M: TM sig.∀R.
247 (∀t.Terminate sig M t) → WRealize sig M R → Realize sig M R.
248 #sig #M #R #HT #HW #t cases (HT … t) #i * #outc #Hloop
249 @(ex_intro … i) @(ex_intro … outc) % // @(HW … i) //
252 lemma loop_eq : ∀sig,f,q,i,j,a,x,y.
253 loop sig i f q a = Some ? x → loop sig j f q a = Some ? y → x = y.
254 #sig #f #q #i #j @(nat_elim2 … i j)
255 [ #n #a #x #y normalize #Hfalse destruct (Hfalse)
256 | #n #a #x #y #H1 normalize #Hfalse destruct (Hfalse)
257 | #n1 #n2 #IH #a #x #y normalize cases (q a) normalize
263 theorem Realize_to_WRealize : ∀sig,M,R.Realize sig M R → WRealize sig M R.
264 #sig #M #R #H1 #inc #i #outc #Hloop
265 cases (H1 inc) #k * #outc1 * #Hloop1 #HR
266 >(loop_eq … Hloop Hloop1) //
269 definition accRealize ≝ λsig.λM:TM sig.λacc:states sig M.λRtrue,Rfalse:relation (tape sig).
271 loop ? i (step sig M) (λc.halt sig M (cstate ?? c)) (initc sig M t) = Some ? outc ∧
272 (cstate ?? outc = acc → Rtrue t (ctape ?? outc)) ∧
273 (cstate ?? outc ≠ acc → Rfalse t (ctape ?? outc)).
277 definition seq_trans ≝ λsig. λM1,M2 : TM sig.
281 if halt sig M1 s1 then 〈inr … (start sig M2), None ?〉
283 let 〈news1,m〉 ≝ trans sig M1 〈s1,a〉 in
286 let 〈news2,m〉 ≝ trans sig M2 〈s2,a〉 in
290 definition seq ≝ λsig. λM1,M2 : TM sig.
292 (FinSum (states sig M1) (states sig M2))
293 (seq_trans sig M1 M2)
294 (inl … (start sig M1))
296 [ inl _ ⇒ false | inr s2 ⇒ halt sig M2 s2]).
298 definition Rcomp ≝ λA.λR1,R2:relation A.λa1,a2.
299 ∃am.R1 a1 am ∧ R2 am a2.
302 definition injectRl ≝ λsig.λM1.λM2.λR.
304 inl … (cstate sig M1 c11) = cstate sig (seq sig M1 M2) c1 ∧
305 inl … (cstate sig M1 c12) = cstate sig (seq sig M1 M2) c2 ∧
306 ctape sig M1 c11 = ctape sig (seq sig M1 M2) c1 ∧
307 ctape sig M1 c12 = ctape sig (seq sig M1 M2) c2 ∧
310 definition injectRr ≝ λsig.λM1.λM2.λR.
312 inr … (cstate sig M2 c21) = cstate sig (seq sig M1 M2) c1 ∧
313 inr … (cstate sig M2 c22) = cstate sig (seq sig M1 M2) c2 ∧
314 ctape sig M2 c21 = ctape sig (seq sig M1 M2) c1 ∧
315 ctape sig M2 c22 = ctape sig (seq sig M1 M2) c2 ∧
318 definition Rlink ≝ λsig.λM1,M2.λc1,c2.
319 ctape sig (seq sig M1 M2) c1 = ctape sig (seq sig M1 M2) c2 ∧
320 cstate sig (seq sig M1 M2) c1 = inl … (halt sig M1) ∧
321 cstate sig (seq sig M1 M2) c2 = inr … (start sig M2). *)
323 interpretation "relation composition" 'compose R1 R2 = (Rcomp ? R1 R2).
325 definition lift_confL ≝
326 λsig,S1,S2,c.match c with
327 [ mk_config s t ⇒ mk_config sig (FinSum S1 S2) (inl … s) t ].
329 definition lift_confR ≝
330 λsig,S1,S2,c.match c with
331 [ mk_config s t ⇒ mk_config sig (FinSum S1 S2) (inr … s) t ].
333 definition halt_liftL ≝
334 λS1,S2,halt.λs:FinSum S1 S2.
337 | inr _ ⇒ true ]. (* should be vacuous in all cases we use halt_liftL *)
339 definition halt_liftR ≝
340 λS1,S2,halt.λs:FinSum S1 S2.
343 | inr s2 ⇒ halt s2 ].
345 lemma p_halt_liftL : ∀sig,S1,S2,halt,c.
346 halt (cstate sig S1 c) =
347 halt_liftL S1 S2 halt (cstate … (lift_confL … c)).
348 #sig #S1 #S2 #halt #c cases c #s #t %
351 lemma trans_liftL : ∀sig,M1,M2,s,a,news,move.
352 halt ? M1 s = false →
353 trans sig M1 〈s,a〉 = 〈news,move〉 →
354 trans sig (seq sig M1 M2) 〈inl … s,a〉 = 〈inl … news,move〉.
355 #sig (*#M1*) * #Q1 #T1 #init1 #halt1 #M2 #s #a #news #move
356 #Hhalt #Htrans whd in ⊢ (??%?); >Hhalt >Htrans %
359 lemma trans_liftR : ∀sig,M1,M2,s,a,news,move.
360 halt ? M2 s = false →
361 trans sig M2 〈s,a〉 = 〈news,move〉 →
362 trans sig (seq sig M1 M2) 〈inr … s,a〉 = 〈inr … news,move〉.
363 #sig #M1 * #Q2 #T2 #init2 #halt2 #s #a #news #move
364 #Hhalt #Htrans whd in ⊢ (??%?); >Hhalt >Htrans %
369 cstate sig M c1 = cstate sig M c2 →
370 ctape sig M c1 = ctape sig M c2 → c1 = c2.
371 #sig #M1 * #s1 #t1 * #s2 #t2 //
374 lemma step_lift_confR : ∀sig,M1,M2,c0.
375 halt ? M2 (cstate ?? c0) = false →
376 step sig (seq sig M1 M2) (lift_confR sig (states ? M1) (states ? M2) c0) =
377 lift_confR sig (states ? M1) (states ? M2) (step sig M2 c0).
378 #sig #M1 (* * #Q1 #T1 #init1 #halt1 *) #M2 * #s #t
379 lapply (refl ? (trans ?? 〈s,current sig t〉))
380 cases (trans ?? 〈s,current sig t〉) in ⊢ (???% → %);
383 | 2,3: #s1 #l1 #Heq #Hhalt
384 |#ls #s1 #rs #Heq #Hhalt ]
385 whd in ⊢ (???(????%)); >Heq
387 whd in ⊢ (??(???%)?); whd in ⊢ (??%?);
388 >(trans_liftR … Heq) //
391 lemma step_lift_confL : ∀sig,M1,M2,c0.
392 halt ? M1 (cstate ?? c0) = false →
393 step sig (seq sig M1 M2) (lift_confL sig (states ? M1) (states ? M2) c0) =
394 lift_confL sig ?? (step sig M1 c0).
395 #sig #M1 (* * #Q1 #T1 #init1 #halt1 *) #M2 * #s #t
396 lapply (refl ? (trans ?? 〈s,current sig t〉))
397 cases (trans ?? 〈s,current sig t〉) in ⊢ (???% → %);
400 | 2,3: #s1 #l1 #Heq #Hhalt
401 |#ls #s1 #rs #Heq #Hhalt ]
402 whd in ⊢ (???(????%)); >Heq
404 whd in ⊢ (??(???%)?); whd in ⊢ (??%?);
405 >(trans_liftL … Heq) //
408 lemma loop_lift : ∀A,B,k,lift,f,g,h,hlift,c1,c2.
409 (∀x.hlift (lift x) = h x) →
410 (∀x.h x = false → lift (f x) = g (lift x)) →
411 loop A k f h c1 = Some ? c2 →
412 loop B k g hlift (lift c1) = Some ? (lift … c2).
413 #A #B #k #lift #f #g #h #hlift #c1 #c2 #Hfg #Hhlift
414 generalize in match c1; elim k
415 [#c0 normalize in ⊢ (??%? → ?); #Hfalse destruct (Hfalse)
416 |#k0 #IH #c0 whd in ⊢ (??%? → ??%?);
417 cases (true_or_false (h c0)) #Hc0 >Hfg >Hc0
418 [ normalize #Heq destruct (Heq) %
419 | normalize <Hhlift // @IH ]
423 lemma loop_liftL : ∀sig,k,M1,M2,c1,c2.
424 loop ? k (step sig M1) (λc.halt sig M1 (cstate ?? c)) c1 = Some ? c2 →
425 loop ? k (step sig (seq sig M1 M2))
426 (λc.halt_liftL ?? (halt sig M1) (cstate ?? c)) (lift_confL … c1) =
427 Some ? (lift_confL … c2).
428 #sig #k #M1 #M2 #c1 #c2 generalize in match c1;
430 [#c0 normalize in ⊢ (??%? → ?); #Hfalse destruct (Hfalse)
431 |#k0 #IH #c0 whd in ⊢ (??%? → ??%?);
432 cases (true_or_false (halt ?? (cstate sig (states ? M1) c0))) #Hc0 >Hc0
433 [ >(?: halt_liftL ?? (halt sig M1) (cstate sig ? (lift_confL … c0)) = true)
434 [ whd in ⊢ (??%? → ??%?); #Hc2 destruct (Hc2) %
436 | >(?: halt_liftL ?? (halt sig M1) (cstate ?? (lift_confL … c0)) = false)
437 [whd in ⊢ (??%? → ??%?); #Hc2 <(IH ? Hc2) @eq_f
442 lemma loop_liftR : ∀sig,k,M1,M2,c1,c2.
443 loop ? k (step sig M2) (λc.halt sig M2 (cstate ?? c)) c1 = Some ? c2 →
444 loop ? k (step sig (seq sig M1 M2))
445 (λc.halt sig (seq sig M1 M2) (cstate ?? c)) (lift_confR … c1) =
446 Some ? (lift_confR … c2).
447 #sig #k #M1 #M2 #c1 #c2 generalize in match c1;
449 [#c0 normalize in ⊢ (??%? → ?); #Hfalse destruct (Hfalse)
450 |#k0 #IH #c0 whd in ⊢ (??%? → ??%?);
451 cases (true_or_false (halt ?? (cstate sig ? c0))) #Hc0 >Hc0
452 [ >(?: halt ? (seq sig M1 M2) (cstate sig ? (lift_confR … c0)) = true)
453 [ whd in ⊢ (??%? → ??%?); #Hc2 destruct (Hc2) %
455 | >(?: halt ? (seq sig M1 M2) (cstate sig ? (lift_confR … c0)) = false)
456 [whd in ⊢ (??%? → ??%?); #Hc2 <(IH ? Hc2) @eq_f
465 ∀A,k,f,p,a,b.loop A k f p a = Some ? b → p b = true.
467 [#a #b normalize #Hfalse destruct
468 |#k0 #IH #a #b whd in ⊢ (??%? → ?); cases (true_or_false (p a)) #Hpa
469 [ >Hpa normalize #H1 destruct //
475 lemma trans_liftL_true : ∀sig,M1,M2,s,a.
477 trans sig (seq sig M1 M2) 〈inl … s,a〉 = 〈inr … (start ? M2),None ?〉.
479 #Hhalt whd in ⊢ (??%?); >Hhalt %
482 lemma eq_ctape_lift_conf_L : ∀sig,S1,S2,outc.
483 ctape sig (FinSum S1 S2) (lift_confL … outc) = ctape … outc.
484 #sig #S1 #S2 #outc cases outc #s #t %
487 lemma eq_ctape_lift_conf_R : ∀sig,S1,S2,outc.
488 ctape sig (FinSum S1 S2) (lift_confR … outc) = ctape … outc.
489 #sig #S1 #S2 #outc cases outc #s #t %
492 theorem sem_seq: ∀sig,M1,M2,R1,R2.
493 Realize sig M1 R1 → Realize sig M2 R2 →
494 Realize sig (seq sig M1 M2) (R1 ∘ R2).
495 #sig #M1 #M2 #R1 #R2 #HR1 #HR2 #t
496 cases (HR1 t) #k1 * #outc1 * #Hloop1 #HM1
497 cases (HR2 (ctape sig (states ? M1) outc1)) #k2 * #outc2 * #Hloop2 #HM2
498 @(ex_intro … (k1+k2)) @(ex_intro … (lift_confR … outc2))
500 [@(loop_merge ???????????
501 (loop_lift ??? (lift_confL sig (states sig M1) (states sig M2))
502 (step sig M1) (step sig (seq sig M1 M2))
503 (λc.halt sig M1 (cstate … c))
504 (λc.halt_liftL ?? (halt sig M1) (cstate … c)) … Hloop1))
506 [ #sl #tl whd in ⊢ (??%? → ?); #Hl %
507 | #sr #tr whd in ⊢ (??%? → ?); #Hr destruct (Hr) ]
508 || #c0 #Hhalt <step_lift_confL //
510 |6:cases outc1 #s1 #t1 %
511 |7:@(loop_lift … (initc ?? (ctape … outc1)) … Hloop2)
513 | #c0 #Hhalt <step_lift_confR // ]
514 |whd in ⊢ (??(???%)?);whd in ⊢ (??%?);
515 generalize in match Hloop1; cases outc1 #sc1 #tc1 #Hloop10
516 >(trans_liftL_true sig M1 M2 ??)
517 [ whd in ⊢ (??%?); whd in ⊢ (???%);
518 @config_eq whd in ⊢ (???%); //
519 | @(loop_Some ?????? Hloop10) ]
521 | @(ex_intro … (ctape ? (FinSum (states ? M1) (states ? M2)) (lift_confL … outc1)))
522 % // >eq_ctape_lift_conf_L >eq_ctape_lift_conf_R //