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_____________________________________________________________*)
13 (* MOVE_CHAR (left) MACHINE
15 Sposta il carattere binario su cui si trova la testina appena prima del primo #
19 (ls,cs,rs can be empty; # is a parameter)
35 include "turing/basic_machines.ma".
36 include "turing/if_machine.ma".
38 definition mcl_states : FinSet → FinSet ≝ λalpha:FinSet.FinProd (initN 5) alpha.
40 definition mcl0 : initN 5 ≝ mk_Sig ?? 0 (leb_true_to_le 1 5 (refl …)).
41 definition mcl1 : initN 5 ≝ mk_Sig ?? 1 (leb_true_to_le 2 5 (refl …)).
42 definition mcl2 : initN 5 ≝ mk_Sig ?? 2 (leb_true_to_le 3 5 (refl …)).
43 definition mcl3 : initN 5 ≝ mk_Sig ?? 3 (leb_true_to_le 4 5 (refl …)).
44 definition mcl4 : initN 5 ≝ mk_Sig ?? 4 (leb_true_to_le 5 5 (refl …)).
46 definition mcl_step ≝ λalpha:FinSet.λsep:alpha.
47 ifTM alpha (test_char ? (λc.¬c==sep))
48 (single_finalTM … (seq … (swap alpha sep) (move_l ?))) (nop ?) tc_true.
53 λalpha:FinSet.λsep:alpha.
54 mk_TM alpha (mcl_states alpha)
57 let q' ≝ pi1 nat (λi.i<5) q' in (* perche' devo passare il predicato ??? *)
59 [ None ⇒ 〈〈mcl4,sep〉,None ?〉
64 [ true ⇒ 〈〈mcl4,sep〉,None ?〉
65 | false ⇒ 〈〈mcl1,a'〉,Some ? 〈a',R〉〉 ]
66 | S q' ⇒ match q' with
68 〈〈mcl2,a'〉,Some ? 〈b,L〉〉
69 | S q' ⇒ match q' with
71 〈〈mcl3,sep〉,Some ? 〈b,L〉〉
72 | S q' ⇒ match q' with
76 〈〈mcl4,sep〉,None ?〉 ] ] ] ] ])
78 (λq.let 〈q',a〉 ≝ q in q' == mcl3 ∨ q' == mcl4).
81 ∀alpha:FinSet.∀sep,a,ls,a0,rs.
83 step alpha (mcl_step alpha sep)
84 (mk_config ?? 〈mcl0,a〉 (mk_tape … ls (Some ? a0) rs)) =
85 mk_config alpha (states ? (mcl_step alpha sep)) 〈mcl1,a0〉
86 (tape_move_right alpha ls a0 rs).
88 [ #a0 #rs #Ha0 whd in ⊢ (??%?);
89 normalize in match (trans ???); >Ha0 %
90 | #a1 #ls #a0 #rs #Ha0 whd in ⊢ (??%?);
91 normalize in match (trans ???); >Ha0 %
96 ∀alpha:FinSet.∀sep,a,ls,a0,rs.
97 step alpha (mcl_step alpha sep)
98 (mk_config ?? 〈mcl1,a〉 (mk_tape … ls (Some ? a0) rs)) =
99 mk_config alpha (states ? (mcl_step alpha sep)) 〈mcl2,a0〉
100 (tape_move_left alpha ls a rs).
101 #alpha #sep #a #ls #a0 * //
105 ∀alpha:FinSet.∀sep,a,ls,a0,rs.
106 step alpha (mcl_step alpha sep)
107 (mk_config ?? 〈mcl2,a〉 (mk_tape … ls (Some ? a0) rs)) =
108 mk_config alpha (states ? (mcl_step alpha sep)) 〈mcl3,sep〉
109 (tape_move_left alpha ls a rs).
110 #alpha #sep #a #ls #a0 * //
114 definition Rmcl_step_true ≝
117 t1 = midtape alpha ls b (a::rs) →
119 t2 = mk_tape alpha (tail ? ls) (option_hd ? ls) (a::b::rs).
121 definition Rmcl_step_false ≝
123 right ? t1 ≠ [] → current alpha t1 ≠ None alpha →
124 current alpha t1 = Some alpha sep ∧ t2 = t1.
126 lemma mcl_trans_init_sep:
128 trans ? (mcl_step alpha sep) 〈〈mcl0,x〉,Some ? sep〉 = 〈〈mcl4,sep〉,None ?〉.
129 #alpha #sep #x normalize >(\b ?) //
132 lemma mcl_trans_init_not_sep:
133 ∀alpha,sep,x,y.y == sep = false →
134 trans ? (mcl_step alpha sep) 〈〈mcl0,x〉,Some ? y〉 = 〈〈mcl1,y〉,Some ? 〈y,R〉〉.
135 #alpha #sep #x #y #H1 normalize >H1 //
142 [inr … (inl … (inr … start_nop)): Rmcl_step_true alpha sep, Rmcl_step_false alpha sep].
145 (sem_test_char …) (sem_seq …(sem_swap …) (sem_move_l …)) (sem_nop …))
146 [#intape #outtape #tapea whd in ⊢ (%→%→%);
147 #Htapea * #tapeb * whd in ⊢ (%→%→?);
148 #Htapeb #Houttape #a #b #ls #rs #Hintape
149 >Hintape in Htapea; #Htapea cases (Htapea ? (refl …)) -Htapea
150 #Hbsep #Htapea % [@(\Pf (injective_notb ? false Hbsep))]
152 |#intape #outtape #tapea whd in ⊢ (%→%→%);
153 cases (current alpha intape)
154 [#_ #_ #_ * #Hfalse @False_ind @Hfalse %
155 |#c #H #Htapea #_ #_ cases (H c (refl …)) #csep #Hintape % //
156 lapply (injective_notb ? true csep) -csep #csep >(\P csep)
162 accRealize alpha (mcl_step alpha sep)
163 〈mcl3,sep〉 (Rmcl_step_true alpha sep) (Rmcl_step_false alpha sep).
164 #alpha #sep cut (∀P:Prop.〈mcl4,sep〉=〈mcl3,sep〉→P)
165 [#P whd in ⊢ ((??(???%?)(???%?))→?); #Hfalse destruct] #Hfalse
168 @(ex_intro … (mk_config ?? 〈mcl4,sep〉 (niltape ?)))
169 % [% [whd in ⊢ (??%?);% |@Hfalse] |#H1 #H2 @False_ind @(absurd ?? H2) %]
170 |#l0 #lt0 @(ex_intro ?? 2)
171 @(ex_intro … (mk_config ?? 〈mcl4,sep〉 (leftof ? l0 lt0)))
172 % [% [whd in ⊢ (??%?);% |@Hfalse] |#H1 #H2 #H3 @False_ind @(absurd ?? H3) %]
173 |#r0 #rt0 @(ex_intro ?? 2)
174 @(ex_intro … (mk_config ?? 〈mcl4,sep〉 (rightof ? r0 rt0)))
175 % [% [whd in ⊢ (??%?);% |@Hfalse] |#H1 #H2 #H3 @False_ind @(absurd ?? H3) %]
176 | #lt #c #rt cases (true_or_false (c == sep)) #Hc
178 @(ex_intro ?? (mk_config ?? 〈mcl4,sep〉 (midtape ? lt c rt)))
180 [ >(\P Hc) >loopM_unfold >loop_S_false // >loop_S_true
181 [ @eq_f whd in ⊢ (??%?); >mcl_trans_init_sep %
182 |>(\P Hc) whd in ⊢(??(???(???%))?); >mcl_trans_init_sep % ]
184 |#_ #H1 #H2 % // normalize >(\P Hc) % ]
185 |@(ex_intro ?? 4) cases rt
188 [ >loopM_unfold >loop_S_false // >mcl_q0_q1 //
189 | normalize in ⊢ (%→?); @Hfalse]
190 | normalize in ⊢ (%→?); #_ #H1 @False_ind @(absurd ?? H1) % ] ]
193 [ >loopM_unfold >loop_S_false // >mcl_q0_q1 //
194 | #_ #a #b #ls #rs #Hb destruct (Hb) %
196 | >mcl_q1_q2 >mcl_q2_q3 cases ls normalize // ] ]
197 | normalize in ⊢ (% → ?); * #Hfalse
205 (* the move_char (variant c) machine *)
206 definition move_char_l ≝
207 λalpha,sep.whileTM alpha (mcl_step alpha sep) 〈mcl3,sep〉.
209 definition R_move_char_l ≝
211 ∀b,a,ls,rs. t1 = midtape alpha ls b (a::rs) →
212 (b = sep → t2 = t1) ∧
213 (∀ls1,ls2.ls = ls1@sep::ls2 →
214 b ≠ sep → memb ? sep ls1 = false →
215 t2 = midtape alpha ls2 sep (a::reverse ? ls1@b::rs)).
217 lemma sem_move_char_l :
219 WRealize alpha (move_char_l alpha sep) (R_move_char_l alpha sep).
220 #alpha #sep #inc #i #outc #Hloop
221 lapply (sem_while … (sem_mcl_step alpha sep) inc i outc Hloop) [%]
222 -Hloop * #t1 * #Hstar @(star_ind_l ??????? Hstar)
223 [ #tapea whd in ⊢ (% → ?); #H1 #b #a #ls #rs #Htapea
225 [ #Hb >Htapea in H1; >Hb #H1 cases (H1 ??)
226 [#_ #H2 >H2 % |*: % #H2 normalize in H2; destruct (H2) ]
227 | #rs1 #rs2 #Hrs #Hb #Hrs1
228 >Htapea in H1; (* normalize in ⊢ (% → ?); *) #H1 cases (H1 ??)
229 [ #Hfalse normalize in Hfalse; @False_ind @(absurd ?? Hb) destruct %
230 |*:% normalize #H2 destruct (H2) ]
232 | #tapea #tapeb #tapec #Hstar1 #HRtrue #IH #HRfalse
233 lapply (IH HRfalse) -IH whd in ⊢ (%→%); #IH
234 #a0 #b0 #ls #rs #Htapea cases (Hstar1 … Htapea)
236 [ #Hfalse @False_ind @(absurd ?? Ha0) //
238 [ #ls2 whd in ⊢ (???%→?); #Hls #_ #_
239 >Hls in Htapeb; #Htapeb normalize in Htapeb;
240 cases (IH … Htapeb) #Houtc #_ >Houtc normalize //
241 | #l0 #ls0 #ls2 #Hls #_ #Hls0
242 cut (l0 ≠ sep ∧ memb … sep ls0 = false)
244 [ % #Hl0 >Hl0 in Hls0; >memb_hd #Hfalse destruct
245 | whd in Hls0:(??%?); cases (sep==l0) in Hls0; normalize #Hfalse
250 #Hl0 -Hls0 #Hls0 >Hls in Htapeb;
251 normalize in ⊢ (%→?); #Htapeb
252 cases (IH … Htapeb) -IH #_ #IH
253 >reverse_cons >associative_append @IH //
258 lemma terminate_move_char_l :
259 ∀alpha,sep.∀t,b,a,ls,rs. t = midtape alpha ls b (a::rs) →
260 (b = sep ∨ memb ? sep ls = true) → Terminate alpha (move_char_l alpha sep) t.
261 #alpha #sep #t #b #a #ls #rs #Ht #Hsep
262 @(terminate_while … (sem_mcl_step alpha sep))
264 |generalize in match Hsep; -Hsep
265 generalize in match Ht; -Ht
266 generalize in match rs; -rs
267 generalize in match a; -a
268 generalize in match b; -b
269 generalize in match t; -t
271 [#t #b #a #rs #Ht #Hsep % #tinit
272 whd in ⊢ (%→?); #H @False_ind
273 cases (H … Ht) #Hb #_ cases Hb #eqb @eqb
274 cases Hsep // whd in ⊢ ((??%?)→?); #abs destruct
275 |#l0 #ls0 #Hind #t #b #a #rs #Ht #Hsep % #tinit
277 cases (H … Ht) #Hbsep #Htinit
278 @(Hind … Htinit) cases Hsep
279 [#Hb @False_ind /2/ | #Hmemb cases (orb_true_l … Hmemb)
280 [#eqsep %1 >(\P eqsep) // | #H %2 //]