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 include "turing/universal/trans_to_tuples.ma".
14 include "turing/universal/uni_step.ma".
16 (* definition zero : ∀n.initN n ≝ λn.mk_Sig ?? 0 (le_O_n n). *)
18 record normalTM : Type[0] ≝
20 pos_no_states : (0 < no_states);
21 ntrans : trans_source no_states → trans_target no_states;
22 nhalt : initN no_states → bool
25 definition normalTM_to_TM ≝ λM:normalTM.
26 mk_TM FinBool (initN (no_states M))
27 (ntrans M) (mk_Sig ?? 0 (pos_no_states M)) (nhalt M).
29 coercion normalTM_to_TM.
31 definition nconfig ≝ λn. config FinBool (initN n).
34 definition normalTM ≝ λn,t,h.
35 λk:0<n.mk_TM FinBool (initN n) t (mk_Sig ?? 0 k) h. *)
37 definition low_config: ∀M:normalTM.nconfig (no_states M) → tape STape ≝
39 let n ≝ no_states M in
43 let q_low ≝ m_bits_of_state n h q in
44 let current_low ≝ match current … (ctape … c) with [ None ⇒ null | Some b ⇒ bit b] in
45 let low_left ≝ map … (λb.〈bit b,false〉) (left … (ctape …c)) in
46 let low_right ≝ map … (λb.〈bit b,false〉) (right … (ctape …c)) in
47 let table ≝ flatten ? (tuples_of_pairs n h (graph_enum ?? t)) in
48 let right ≝ q_low@〈current_low,false〉::〈grid,false〉::table@〈grid,false〉::low_right in
49 mk_tape STape (〈grid,false〉::low_left) (option_hd … right) (tail … right).
51 lemma low_config_eq: ∀t,M,c. t = low_config M c →
52 ∃low_left,low_right,table,q_low_hd,q_low_tl,c_low.
53 low_left = map … (λb.〈bit b,false〉) (left … (ctape …c)) ∧
54 low_right = map … (λb.〈bit b,false〉) (right … (ctape …c)) ∧
55 table = flatten ? (tuples_of_pairs (no_states M) (nhalt M) (graph_enum ?? (ntrans M))) ∧
56 〈q_low_hd,false〉::q_low_tl = m_bits_of_state (no_states M) (nhalt M) (cstate … c) ∧
57 c_low = match current … (ctape … c) with [ None ⇒ null| Some b ⇒ bit b] ∧
58 t = midtape STape (〈grid,false〉::low_left) 〈q_low_hd,false〉 (q_low_tl@〈c_low,false〉::〈grid,false〉::table@〈grid,false〉::low_right).
60 @(ex_intro … (map … (λb.〈bit b,false〉) (left … (ctape …c))))
61 @(ex_intro … (map … (λb.〈bit b,false〉) (right … (ctape …c))))
62 @(ex_intro … (flatten ? (tuples_of_pairs (no_states M) (nhalt M) (graph_enum ?? (ntrans M)))))
63 @(ex_intro … (\fst (hd ? (m_bits_of_state (no_states M) (nhalt M) (cstate … c)) 〈bit true,false〉)))
64 @(ex_intro … (tail ? (m_bits_of_state (no_states M) (nhalt M) (cstate … c))))
65 @(ex_intro … (match current … (ctape … c) with [ None ⇒ null| Some b ⇒ bit b]))
66 % [% [% [% [% // | // ] | // ] | // ] | >eqt //]
69 definition low_step_R_true ≝ λt1,t2.
71 ∀c: nconfig (no_states M).
73 halt ? M (cstate … c) = false ∧
74 t2 = low_config M (step ? M c).
76 lemma unistep_to_low_step: ∀t1,t2.
77 R_uni_step_true t1 t2 → low_step_R_true t1 t2.
78 #t1 #t2 (* whd in ⊢ (%→%); *) #Huni_step #M #c #eqt1
79 cases (low_config_eq … eqt1)
80 #low_left * #low_right * #table * #q_low_hd * #q_low_tl * #current_low
81 ***** #Hlow_left #Hlow_right #Htable #Hq_low #Hcurrent_low #Ht1
82 lapply (Huni_step ??????????????? Ht1)
83 whd in match (low_config M c);
85 definition R_uni_step_true ≝ λt1,t2.
86 ∀n,t0,table,s0,s1,c0,c1,ls,rs,curconfig,newconfig,mv.
87 table_TM (S n) (〈t0,false〉::table) →
88 match_in_table (S n) (〈s0,false〉::curconfig) 〈c0,false〉
89 (〈s1,false〉::newconfig) 〈c1,false〉 〈mv,false〉 (〈t0,false〉::table) →
90 legal_tape ls 〈c0,false〉 rs →
91 t1 = midtape STape (〈grid,false〉::ls) 〈s0,false〉
92 (curconfig@〈c0,false〉::〈grid,false〉::〈t0,false〉::table@〈grid,false〉::rs) →
93 ∀t1'.t1' = lift_tape ls 〈c0,false〉 rs →
96 (t2 = midtape STape (〈grid,false〉::ls1) 〈s1,false〉
97 (newconfig@〈c2,false〉::〈grid,false〉::〈t0,false〉::table@〈grid,false〉::rs1) ∧
98 lift_tape ls1 〈c2,false〉 rs1 =
99 tape_move STape t1' (map_move c1 mv) ∧ legal_tape ls1 〈c2,false〉 rs1).
102 definition low_step_R_false ≝ λt1,t2.
104 ∀c: nconfig (no_states M).
105 t1 = low_config M c → halt ? M (cstate … c) = true ∧ t1 = t2.
107 definition low_R ≝ λM,qstart,R,t1,t2.
108 ∀tape1. t1 = low_config M (mk_config ?? qstart tape1) →
109 ∃q,tape2.R tape1 tape2 ∧
110 halt ? M q = true ∧ t2 = low_config M (mk_config ?? q tape2).
112 definition R_TM ≝ λsig.λM:TM sig.λq.λt1,t2.
114 loop ? i (step sig M) (λc.halt sig M (cstate ?? c)) (mk_config ?? q t1) = Some ? outc ∧
115 t2 = (ctape ?? outc).
118 definition universal_R ≝ λM,R,t1,t2.
122 t1 = low_config M (initc ? M tape1) ∧
123 ∃q.halt ? M q = true → t2 = low_config M (mk_config ?? q tape2).*)
125 axiom uni_step: TM STape.
126 axiom us_acc: states ? uni_step.
128 axiom sem_uni_step: accRealize ? uni_step us_acc low_step_R_true low_step_R_false.
130 definition universalTM ≝ whileTM ? uni_step us_acc.
132 theorem sem_universal: ∀M:normalTM. ∀qstart.
133 WRealize ? universalTM (low_R M qstart (R_TM FinBool M qstart)).
134 #M #q #intape #i #outc #Hloop
135 lapply (sem_while … sem_uni_step intape i outc Hloop)
137 * #ta * #Hstar generalize in match q; -q
138 @(star_ind_l ??????? Hstar)
139 [#tb #q0 whd in ⊢ (%→?); #Htb #tape1 #Htb1
140 cases (Htb … Htb1) -Htb #Hhalt #Htb
144 [ whd @(ex_intro … 1) @(ex_intro … (mk_config … q0 tape1))
145 % [|%] whd in ⊢ (??%?); >Hhalt %
149 |#tb #tc #td whd in ⊢ (%→?); #Htc #Hstar1 #IH
151 lapply (IH (\fst (trans ? M 〈q,current ? tape1〉)) Htd) -IH
152 #IH cases (Htc … Htb); -Htc #Hhaltq
153 whd in match (step ???); >(eq_pair_fst_snd ?? (trans ???))
154 #Htc change with (mk_config ????) in Htc:(???(??%));
155 cases (IH ? Htc) #q1 * #tape2 * * #HRTM #Hhaltq1 #Houtc
156 @(ex_intro … q1) @(ex_intro … tape2) %
158 [cases HRTM #k * #outc1 * #Hloop #Houtc1
159 @(ex_intro … (S k)) @(ex_intro … outc1) %
160 [>loop_S_false [2://] whd in match (step ???);
161 >(eq_pair_fst_snd ?? (trans ???)) @Hloop
170 lemma R_TM_to_R: ∀sig,M,R. ∀t1,t2.
171 WRealize sig M R → R_TM ? M (start ? M) t1 t2 → R t1 t2.
172 #sig #M #R #t1 #t2 whd in ⊢ (%→?); #HMR * #i * #outc *
173 #Hloop #Ht2 >Ht2 @(HMR … Hloop)
176 axiom WRealize_to_WRealize: ∀sig,M,R1,R2.
177 (∀t1,t2.R1 t1 t2 → R2 t1 t2) → WRealize sig M R1 → WRealize ? M R2.
179 theorem sem_universal2: ∀M:normalTM. ∀R.
180 WRealize ? M R → WRealize ? universalTM (low_R M (start ? M) R).
181 #M #R #HMR lapply (sem_universal … M (start ? M)) @WRealize_to_WRealize
182 #t1 #t2 whd in ⊢ (%→%); #H #tape1 #Htape1 cases (H ? Htape1)
183 #q * #tape2 * * #HRTM #Hhalt #Ht2 @(ex_intro … q) @(ex_intro … tape2)
184 % [% [@(R_TM_to_R … HRTM) @HMR | //] | //]