X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Fmatita%2Flib%2Fturing%2Funiversal%2Fcopy.ma;h=ae6f0e6cd92c0d73447dde060cf96f8cb435e867;hb=a386e0eb6b20909ae78c825203d77647b8fde30c;hp=2978b5cc4cdaf1d64158ff9f34eb963ed7e89cae;hpb=ed36a3d3f81cf251c41bbe1d208376bb0709c600;p=helm.git

diff --git a/matita/matita/lib/turing/universal/copy.ma b/matita/matita/lib/turing/universal/copy.ma
index 2978b5cc4..ae6f0e6cd 100644
--- a/matita/matita/lib/turing/universal/copy.ma
+++ b/matita/matita/lib/turing/universal/copy.ma
@@ -10,21 +10,20 @@
       V_____________________________________________________________*)
 
 
-(* COMPARE BIT
-
-*)
-
 include "turing/universal/tuples.ma".
 
 definition write_states ≝ initN 2.
 
+definition wr0 : write_states ≝ mk_Sig ?? 0 (leb_true_to_le 1 2 (refl …)).
+definition wr1 : write_states ≝ mk_Sig ?? 1 (leb_true_to_le 2 2 (refl …)).
+
 definition write ≝ λalpha,c.
   mk_TM alpha write_states
   (λp.let 〈q,a〉 ≝ p in
-    match q with 
-    [ O ⇒ 〈1,Some ? 〈c,N〉〉
-    | S _ ⇒ 〈1,None ?〉 ])
-  O (λx.x == 1).
+    match pi1 … q with 
+    [ O ⇒ 〈wr1,Some ? 〈c,N〉〉
+    | S _ ⇒ 〈wr1,None ?〉 ])
+  wr0 (λx.x == wr1).
   
 definition R_write ≝ λalpha,c,t1,t2.
   ∀ls,x,rs.t1 = midtape alpha ls x rs → t2 = midtape alpha ls c rs.
@@ -44,12 +43,11 @@ definition copy_step_subcase ≝
 
 definition R_copy_step_subcase ≝ 
   λalpha,c,RelseM,t1,t2.
-    ∀ls,x,rs.t1 = midtape (FinProd … alpha FinBool) ls 〈x,true〉 rs → 
-    (x = c ∧
-     ∀a,l1,x0,a0,l2,l3. (∀c.memb ? c l1 = true → is_marked ? c = false) → 
-     ls = l1@〈a0,false〉::〈x0,true〉::l2 → 
-     rs = 〈a,false〉::l3 → 
-     t2 = midtape ? (〈x,false〉::l1@〈a0,true〉::〈x,false〉::l2) 〈a,true〉 l3) ∨
+    ∀a,l1,x0,a0,l2,x,l3.
+    t1 = midtape (FinProd … alpha FinBool) (l1@〈a0,false〉::〈x0,true〉::l2) 
+         〈x,true〉 (〈a,false〉::l3) → 
+    (∀c.memb ? c l1 = true → is_marked ? c = false) →          
+    (x = c ∧ t2 = midtape ? (〈x,false〉::l1@〈a0,true〉::〈x,false〉::l2) 〈a,true〉 l3) ∨
     (x ≠ c ∧ RelseM t1 t2).
     
 axiom sem_copy_step_subcase : 
@@ -75,41 +73,375 @@ else if current = 1,tt
         mark;
         move_r;
         advance_to_mark_r;
-else nop
+else if current = null 
+   then advance_mark_r;
+        move_l;
+        advance_to_mark_l
+        adv_mark_r;
+        move_r;
+        advance_to_mark_r
 *)
 
+definition nocopy_subcase ≝
+  ifTM STape (test_char ? (λx:STape.x == 〈null,true〉))
+    (seq ? (adv_mark_r …)
+      (seq ? (move_l …)
+        (seq ? (adv_to_mark_l … (is_marked ?))
+          (seq ? (adv_mark_r …)
+            (seq ? (move_r …) (adv_to_mark_r … (is_marked ?)))))))
+    (nop ?) tc_true.
+
+definition R_nocopy_subcase ≝ 
+  λt1,t2.
+    ∀a,l1,x0,a0,l2,x,l3.
+    t1 = midtape STape (l1@〈a0,false〉::〈x0,true〉::l2) 
+         〈x,true〉 (〈a,false〉::l3) → 
+    (∀c.memb ? c l1 = true → is_marked ? c = false) →          
+    (x = null ∧
+     t2 = midtape ? (〈x,false〉::l1@〈a0,true〉::〈x0,false〉::l2) 〈a,true〉 l3) ∨
+    (x ≠ null ∧ t2 = t1).
+    
+axiom sem_nocopy_subcase : Realize ? nocopy_subcase R_nocopy_subcase.
+(* #intape
+cases (sem_if ? (test_char ? (λx:STape.x == 〈null,true〉)) ?????? tc_true
+ (sem_test_char ? (λx:STape.x == 〈null,true〉))
+        (sem_seq … (sem_adv_mark_r …)
+           (sem_seq … (sem_move_l …)
+             (sem_seq … (sem_adv_to_mark_l … (is_marked ?))
+               (sem_seq … (sem_adv_mark_r …)
+                 (sem_seq … (sem_move_r …) (sem_adv_to_mark_r … (is_marked ?))
+                 ))))) (sem_nop ?) intape)
+#k * #outc * #Hloop #HR @(ex_intro ?? k) @(ex_intro ?? outc)  % [@Hloop] -Hloop
+cases HR -HR
+[| * #ta * whd in ⊢ (%→%→?); #Hta #Houtc
+   #ls #x #rs #Hintape %2  >Hintape in Hta; #Hta cases (Hta ? (refl ??)) -Hta #Hx #Hta %
+   [ lapply (\Pf Hx) @not_to_not #Hx' >Hx' %
+   | <Hta @Houtc ] ]
+@daemon
+qed. *)
+
 definition copy_step ≝
   ifTM ? (test_char STape (λc.is_bit (\fst c)))
   (single_finalTM ? (copy_step_subcase FSUnialpha (bit false)
-    (copy_step_subcase FSUnialpha (bit true) (nop ?))))
+    (copy_step_subcase FSUnialpha (bit true) nocopy_subcase)))
   (nop ?)
   tc_true.
   
 definition R_copy_step_true ≝ 
   λt1,t2.
-    ∀ls,c,rs.t1 = midtape (FinProd … FSUnialpha FinBool) ls 〈c,true〉 rs → 
-    ∃x. c = bit x ∧
-    (∀a,l1,c0,a0,l2,l3. (∀y.memb ? y l1 = true → is_marked ? y = false) → 
-     ls = l1@〈a0,false〉::〈c0,true〉::l2 → 
-     rs = 〈a,false〉::l3 → 
-     t2 = midtape STape (〈bit x,false〉::l1@〈a0,true〉::〈bit x,false〉::l2) 〈a,true〉 l3).
-
+    ∀ls,c,rs. t1 = midtape STape ls 〈c,true〉 rs → 
+    bit_or_null c = true ∧
+    (∀a,l1,x0,a0,l2,l3.
+     ls = (l1@〈a0,false〉::〈x0,true〉::l2) → 
+     rs = (〈a,false〉::l3) → 
+     no_marks l1 →          
+     ((∃x. c = bit x ∧
+      t2 = midtape STape (〈bit x,false〉::l1@〈a0,true〉::〈bit x,false〉::l2) 〈a,true〉 l3) ∨
+      (c = null ∧
+      t2 = midtape ? (〈null,false〉::l1@〈a0,true〉::〈x0,false〉::l2) 〈a,true〉 l3))).
+     
 definition R_copy_step_false ≝ 
   λt1,t2.
    ∀ls,c,rs.t1 = midtape (FinProd … FSUnialpha FinBool) ls c rs → 
-   is_bit (\fst c) = false ∧ t2 = t1.
+   bit_or_null (\fst c) = false ∧ t2 = t1.
+
+axiom sem_copy_step : 
+  accRealize ? copy_step (inr … (inl … (inr … start_nop))) R_copy_step_true R_copy_step_false.
 
-axiom sem_comp_step : 
-  accRealize ? copy_step (inr … (inl … (inr … 0))) R_copy_step_true R_copy_step_false.
+(*
+1) il primo carattere è marcato
+2) l'ultimo carattere è l'unico che può essere null, gli altri sono bit
+3) il terminatore non è né bit, né null
+*)
    
-definition copy ≝ whileTM ? copy_step (inr … (inl … (inr … 0))).
+definition copy0 ≝ whileTM ? copy_step (inr … (inl … (inr … start_nop))).
+
+let rec merge_config (l1,l2:list STape) ≝ 
+  match l1 with
+  [ nil ⇒ nil ?
+  | cons p1 l1' ⇒ match l2 with
+    [ nil ⇒ nil ? 
+    | cons p2 l2' ⇒ 
+           let 〈c1,b1〉 ≝ p1 in let 〈c2,b2〉 ≝ p2 in
+           match c2 with
+           [ null ⇒ p1
+           | _ ⇒ p2 ] :: merge_config l1' l2' ] ].
+           
+lemma merge_config_append :
+ ∀l1,l2,l3,l4.|l1| = |l2| → 
+ merge_config (l1@l3) (l2@l4) = merge_config l1 l2@merge_config l3 l4.
+#l1 #l2 #l3 #l4 #Hlen @(list_ind2 … Hlen)
+[normalize //
+| #t1 #t2 * #c1 #b1 * #c2 #b2 #IH whd in ⊢ (??%%); >IH % ]
+qed.
+
+definition R_copy0 ≝ λt1,t2.
+  ∀ls,c,c0,rs,l1,l3,l4.
+  t1 = midtape STape (l3@l4@〈c0,true〉::ls) 〈c,true〉 (l1@rs) → 
+  no_marks l1 → no_marks (l3@l4) → |l1| = |l4| → 
+  ∀l1',bv.〈c,false〉::l1 = l1'@[〈comma,bv〉] → only_bits_or_nulls l1' → 
+  ∀l4',bg.l4@[〈c0,false〉] = 〈grid,bg〉::l4' → only_bits_or_nulls l4' → 
+  (c = comma ∧ t2 = t1) ∨
+  (c ≠ comma ∧ 
+    t2 = midtape ? (reverse ? l1'@l3@〈grid,true〉::
+                  merge_config l4' (reverse ? l1')@ls) 
+     〈comma,true〉 rs).
+     
+lemma inj_append_singleton_l1 :
+  ∀A.∀l1,l2:list A.∀a1,a2.l1@[a1] = l2@[a2] → l1 = l2.
+#A #l1 #l2 #a1 #a2 #H lapply (eq_f … (reverse ?) … H)
+>reverse_append >reverse_append normalize #H1 destruct
+lapply (eq_f … (reverse ?) … e0) >reverse_reverse >reverse_reverse //
+qed.
+
+lemma inj_append_singleton_l2 :
+  ∀A.∀l1,l2:list A.∀a1,a2.l1@[a1] = l2@[a2] → a1 = a2.
+#A #l1 #l2 #a1 #a2 #H lapply (eq_f … (reverse ?) … H)
+>reverse_append >reverse_append normalize #H1 destruct %
+qed.
+
+axiom length_reverse : ∀A,l.|reverse A l| = |l|.
+
+lemma wsem_copy0 : WRealize ? copy0 R_copy0.
+#intape #k #outc #Hloop 
+lapply (sem_while … sem_copy_step intape k outc Hloop) [%] -Hloop
+* #ta * #Hstar @(star_ind_l ??????? Hstar)
+[ #tb whd in ⊢ (%→?); #Hleft
+  #ls #c #c0 #rs #l1 #l3 #l4 #Htb #Hl1nomarks #Hl3l4nomarks #Hlen #l1' #bv
+  #Hl1 #Hl1bits #l4' #bg #Hl4 #Hl4bits
+  cases (Hleft … Htb) -Hleft #Hc #Houtc % %
+  [ generalize in match Hl1bits; -Hl1bits cases l1' in Hl1;
+    [ normalize #Hl1 #c1 destruct (Hl1) %
+    | * #c' #b' #l0 #Heq normalize in Heq; destruct (Heq)
+      #Hl1bits lapply (Hl1bits 〈c',false〉 ?) [ @memb_hd ] 
+      >Hc #Hfalse destruct ]
+  | @Houtc ]
+| #tb #tc #td whd in ⊢ (%→?→(?→%)→%→?); #Htc #Hstar1 #Hind #Htd
+  lapply (Hind Htd) -Hind #Hind
+  #ls #c #c0 #rs #l1 #l3 #l4 #Htb #Hl1nomarks #Hl3l4nomarks #Hlen #l1' #bv
+  #Hl1 #Hl1bits #l4' #bg #Hl4 #Hl4bits %2
+  cases (Htc … Htb) -Htc #Hcbitnull #Htc
+  % [ % #Hc' >Hc' in Hcbitnull; normalize #Hfalse destruct (Hfalse) ]
+  cut (|l1| = |reverse ? l4|) [@daemon] #Hlen1
+  @(list_cases_2 … Hlen1)
+  [ (* case l1 = [] is discriminated because l1 contains at least comma *)
+    #Hl1nil @False_ind >Hl1nil in Hl1; cases l1' normalize
+    [ #Hl1 destruct normalize in Hcbitnull; destruct (Hcbitnull)
+    | #p0 #l0 normalize #Hfalse destruct (Hfalse) cases l0 in e0;
+      [ normalize #Hfalse1 destruct (Hfalse1)
+      | #p0' #l0' normalize #Hfalse1 destruct (Hfalse1) ] ]
+  | (* case c::l1 = c::a::l1'' *)
+    * #a #ba * #a0 #ba0 #l1'' #l4'' #Hl1cons #Hl4cons
+    lapply (eq_f ?? (reverse ?) ?? Hl4cons) >reverse_reverse >reverse_cons -Hl4cons #Hl4cons
+    cut (ba = false) 
+    [ >Hl1cons in Hl1nomarks; #Hl1nomarks lapply (Hl1nomarks 〈a,ba〉 ?)
+      [ @memb_hd | normalize // ] ] #Hba
+    cut (ba0 = false) 
+    [ >Hl4cons in Hl3l4nomarks; #Hl3l4nomarks lapply (Hl3l4nomarks 〈a0,ba0〉 ?)
+      [ @memb_append_l2 @memb_append_l2 @memb_hd | normalize // ] ] #Hba0
+    >Hba0 in Hl4cons; >Hba in Hl1cons; -Hba0 -Hba #Hl1cons #Hl4cons
+    >Hl4cons in Htc; >Hl1cons #Htc
+    lapply (Htc a (l3@reverse ? l4'') c0 a0 ls (l1''@rs) ? (refl ??) ?)
+    [ #x #Hx @Hl3l4nomarks >Hl4cons <associative_append
+      @memb_append_l1 @Hx
+    | >associative_append >associative_append %
+    | -Htc
+      cut (∃la.l1' = 〈c,false〉::la)
+      [ >Hl1cons in Hl1; cases l1'
+        [normalize #Hfalse destruct (Hfalse)
+        | #p #la normalize #Hla destruct (Hla) @(ex_intro ?? la) % ] ]
+      * #la #Hla
+      cut (∃lb.l4' = lb@[〈c0,false〉])
+      [ >Hl4cons in Hl4;
+        @(list_elim_left … l4')
+        [ #Heq lapply (eq_f … (length ?) … Heq)
+          >length_append >length_append 
+          >commutative_plus normalize >commutative_plus normalize
+          #Hfalse destruct
+        | #a1 #tl #_ #Heq 
+          >(inj_append_singleton_l2 ? (reverse ? l4''@[〈a0,false〉]) (〈grid,bg〉::tl) 〈c0,false〉 a1 Heq)
+          @ex_intro //
+      ] ] * #lb #Hlb
+      cut (|lb| = |reverse ? la|) 
+      [ >Hla in Hl1; >Hlb in Hl4; #Hl4 #Hl1
+        >(?:l1 = la@[〈comma,bv〉]) in Hlen;
+        [|normalize in Hl1; destruct (Hl1) %]
+        >(?:l4 = 〈grid,bg〉::lb)
+        [|@(inj_append_singleton_l1 ?? (〈grid,bg〉::lb) ?? Hl4) ]
+        >length_append >commutative_plus >length_reverse
+        normalize #Hlalb destruct (Hlalb) //
+      ] #Hlen2
+      *
+      (* by hyp on the first iteration step, 
+         we consider whether c = bit x or c = null *)
+      (* c = bit x *)
+      [ * #x * #Hx #Htc 
+        lapply (Hind (〈bit x,false〉::ls) a a0 rs l1'' 
+                (〈bit x,false〉::l3) (reverse ? l4'') ????) 
+        [ >Hl1cons in Hlen; >Hl4cons >length_append >commutative_plus 
+          normalize #Hlen destruct (Hlen) //
+        | #x0 #Hx0 cases (orb_true_l … Hx0)
+          [ #Hx0eq >(\P Hx0eq) %
+          | -Hx0 #Hx0 @Hl3l4nomarks >Hl4cons
+            <associative_append @memb_append_l1 // ]
+        | #x0 #Hx0 @Hl1nomarks >Hl1cons @memb_cons //
+        | >Htc >associative_append % 
+        | -Hind 
+          <Hl1cons <Hl4cons #Hind lapply (Hind la bv ?? lb bg ??)
+          [ #x0 #Hx0 @Hl4bits >Hlb @memb_append_l1 //
+          | >Hlb in Hl4; normalize in ⊢ (%→?); #Hl4
+            @(inj_append_singleton_l1 ? l4 (〈grid,bg〉::lb) … Hl4)
+          | #x0 #Hx0 @Hl1bits >Hla @memb_cons //
+          | >Hla in Hl1; normalize in ⊢ (%→?); #Hl1
+            destruct (Hl1) // ] -Hind
+          (* by IH, we proceed by cases, whether a = comma 
+             (consequently several lists = []) or not *)          
+          *
+          [ * #Ha #Houtc1
+(*           cut (l1 = [〈a,false〉])
+           [ cases l1'' in Hl1cons; // #y #ly #Hly
+             >Hly in Hl1; cases l1' in Hl1bits;
+             [ #_ normalize #Hfalse destruct (Hfalse)
+             | #p #lp #Hl1bits normalize #Heq destruct (Heq)
+               @False_ind lapply (Hl1bits 〈a,false〉 ?)
+               [ cases lp in e0;
+                 [ normalize #Hfalse destruct (Hfalse)
+                 | #p0 #lp0 normalize in ⊢ (%→?); #Heq destruct (Heq)
+                   @memb_cons @memb_hd ]
+               | >Ha normalize #Hfalse destruct (Hfalse) ]
+             ]
+           ] #Hl1a
+           cut (l4 = [〈a0,false〉])
+           [ generalize in match Hl4bits; cases l4' in Hl4;
+             [ >Hl4cons #Hfalse #_ 
+               lapply (inj_append_singleton_l1 ?? [] ?? Hfalse)
+               cases (reverse ? l4'') normalize
+               [ #Hfalse1 | #p0 #lp0 #Hfalse1 ] destruct (Hfalse1)
+             | #p #lp 
+           
+             cases l4'' in Hl4cons; // #y #ly #Hly
+             >Hly in Hl4; cases l4' in Hl4bits;
+             [ #_ >reverse_cons #Hfalse
+               lapply (inj_append_singleton_l1 ?? [] ?? Hfalse)
+               -Hfalse cases ly normalize
+               [ #Hfalse | #p #Hp #Hfalse ] destruct (Hfalse)
+                
+             | #p #lp #Hl1bits normalize #Heq destruct (Heq)
+               @False_ind lapply (Hl1bits 〈a,false〉 ?)
+               [ cases lp in e0;
+                 [ normalize #Hfalse destruct (Hfalse)
+                 | #p0 #lp0 normalize in ⊢ (%→?); #Heq destruct (Heq)
+                   @memb_cons @memb_hd ]
+               | >Ha normalize #Hfalse destruct (Hfalse) ]
+             ]
+           ] #Hl1a
+             
+              >Hla normalize #Hl1 destruct (Hl1) lapply (inj_append_ @False_ind
+             
+           cut (l1'' = [] ∧ l4'' = [])
+           [ % [ >Hla in Hl1; normalize #Hl1 destruct (Hl1)
+           
+            cases l1'' in Hl1bits;
+                
+                 [ #_ normalize #H *)
+           cut (la = [] ∧ lb = [] ∧ l1'' = [] ∧ l4'' = [])
+           [ @daemon ] * * * #Hla1 #Hlb1 #Hl1nil #Hl4nil
+           >Hl1cons in Hl1; >Hla
+           >Houtc1 >Htc #Hl1
+           >Hl4cons in Hl4; >Hlb #Hl4
+           >Hla1 >Hlb1 >Hl1nil >Hl4nil >Hx
+           cut (a0 = grid) [ @daemon ] #Ha0 <Ha <Ha0
+           normalize in ⊢ (??(??%?%)(??%?%)); >associative_append %
+          | * #Ha #Houtc1 >Houtc1 @eq_f3 //
+            >Hla >reverse_cons >associative_append @eq_f
+            >Hx whd in ⊢ (??%?); @eq_f whd in ⊢ (???%); @eq_f @eq_f
+            >Hlb >append_cons @eq_f2 // >(merge_config_append … Hlen2) %            
+          ]
+       ]
+    | (* c = null *)
+      * #Hc #Htc 
+      lapply (Hind (〈c0,false〉::ls) a a0 rs l1'' (〈null,false〉::l3) (reverse ? l4'') ????)
+      [  >Hl1cons in Hlen; >Hl4cons >length_append >commutative_plus normalize
+         #Hlen destruct (Hlen) @e0
+      | #x0 #Hx0 cases (memb_append STape ? [〈null,false〉] (l3@reverse ? l4'') … Hx0) -Hx0 #Hx0
+        [ >(memb_single … Hx0) %
+        | @Hl3l4nomarks cases (memb_append … Hx0) -Hx0 #Hx0
+          [ @memb_append_l1 //
+          | @memb_append_l2 >Hl4cons @memb_append_l1 // ]
+        ]
+      | >Hl1cons #x' #Hx0 @Hl1nomarks >Hl1cons @memb_cons //
+      | >Htc @eq_f3 // >associative_append % ] -Hind <Hl1cons <Hl4cons #Hind
+        lapply (Hind la bv ?? lb bg ??)
+          [ #x0 #Hx0 @Hl4bits >Hlb @memb_append_l1 //
+          | >Hlb in Hl4; normalize in ⊢ (%→?); #Hl4
+            @(inj_append_singleton_l1 ? l4 (〈grid,bg〉::lb) … Hl4)
+          | #x0 #Hx0 @Hl1bits >Hla @memb_cons //
+          | >Hla in Hl1; normalize in ⊢ (%→?); #Hl1
+            destruct (Hl1) // ] -Hind *
+          (* by IH, we proceed by cases, whether a = comma 
+             (consequently several lists = []) or not *)          
+          [ * #Ha #Houtc1 >Hl1cons in Hl1; >Hla
+           >Houtc1 >Htc #Hl1
+           >Hl4cons in Hl4; >Hlb #Hl4
+           cut (la = [] ∧ lb = [] ∧ l1'' = [] ∧ l4'' = []) 
+           [@daemon] * * * #Hla1 #Hlb1 #Hl1nil #Hl4nil
+           >Hla1 >Hlb1 >Hl1nil >Hl4nil >Hc
+           cut (a0 = grid) [ @daemon ] #Ha0 <Ha <Ha0
+           normalize in ⊢ (??(??%?%)(??%?%)); >associative_append %
+          | * #Ha #Houtc1 >Houtc1 @eq_f3 //
+            >Hla >reverse_cons >associative_append @eq_f
+            >Hc whd in ⊢ (??%?); @eq_f whd in ⊢ (???%); @eq_f @eq_f
+            >Hlb >append_cons @eq_f2 // >(merge_config_append … Hlen2) %
+          ]
+       ]
+]]]
+qed.
+
+definition merge_char ≝ λc1,c2.
+  match c2 with
+  [ null ⇒ c1
+  | _ ⇒ c2 ].
+  
+lemma merge_cons : 
+  ∀c1,c2,conf1,conf2.
+  merge_config (〈c1,false〉::conf1) (〈c2,false〉::conf2) = 
+    〈merge_char c1 c2,false〉::merge_config conf1 conf2.
+#c1 #c2 #conf1 #conf2 normalize @eq_f2 //
+cases c2 /2/
+qed.
+
+lemma merge_config_c_nil : 
+  ∀c.merge_config c [] = [].
+#c cases c normalize //
+qed.
+
+axiom reverse_merge_config :
+  ∀c1,c2.|c1| = |c2| → reverse ? (merge_config c1 c2) = 
+    merge_config (reverse ? c1) (reverse ? c2).        
+
+definition copy
+≝ 
+  seq STape (move_l …) (seq ? (adv_to_mark_l … (is_marked ?))
+   (seq ? (clear_mark …) (seq ? (adv_to_mark_r … (is_marked ?)) (clear_mark …)))).
+
+(*
+   s0, s1 = caratteri di testa dello stato
+   c0 = carattere corrente del nastro oggetto
+   c1 = carattere in scrittura sul nastro oggetto
+   
+   questa dimostrazione sfrutta il fatto che 
+   merge_config (l0@[c0]) (l1@[c1]) = l1@[merge_char c0 c1] 
+   se l0 e l1 non contengono null
+*)
 
 definition R_copy ≝ λt1,t2.
-  ∀ls,c,rs. ∀l1,d,l2,l3,l4,l5,c0.
-  t1 = midtape ? ls 〈c,true〉 rs → 
-  (* l1 è la stringa sorgente da copiare, l4@〈c0,true〉 è la sua destinazione *)
-  〈c,false〉::rs = l1@〈d,false〉::l2 → only_bits l1 → is_bit d = false → 
-   ls = l3@l4@〈c0,true〉::l5 → |l4@[〈c0,true〉]| = |l1| → 
-   no_marks (l3@l4) → 
-  (∀l4',d'.l4@[〈c0,false〉] = 〈d',false〉::l4' → 
-   t2 = midtape STape (reverse ? l1@l3@〈d',true〉::l4'@l5) 〈d,true〉 l2).
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+  ∀ls,s0,s1,c0,c1,rs,l1,l3,l4.
+  t1 = midtape STape (l3@〈grid,false〉::〈c0,false〉::l4@〈s0,true〉::ls) 〈s1,true〉 (l1@〈c1,false〉::〈comma,false〉::rs) → 
+  no_marks l1 → no_marks l3 → no_marks l4 → |l1| = |l4| → 
+  only_bits (l4@[〈s0,true〉]) → only_bits (〈s1,true〉::l1) → 
+  bit_or_null c0 = true → bit_or_null c1 = true → 
+  t2 = midtape STape (〈c1,false〉::reverse ? l1@〈s1,false〉::l3@〈grid,false〉::
+                      〈merge_char c0 c1,false〉::reverse ? l1@〈s1,false〉::ls)
+       〈comma,false〉 rs.
+
+axiom sem_copy : Realize ? copy R_copy.
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