From 4aa431513ffa0ce0accf81e6e9ea4b9314d468e3 Mon Sep 17 00:00:00 2001
From: Wilmer Ricciotti <ricciott@cs.unibo.it>
Date: Thu, 3 Oct 2013 15:07:11 +0000
Subject: [PATCH] Adds transformation of generic monotape machines into
 machines using a binary alphabet (first commit, doesn't typecheck)

---
 .../lib/turing/multi_universal/binaryTM.ma    | 120 ++++++++++++++++++
 1 file changed, 120 insertions(+)
 create mode 100644 matita/matita/lib/turing/multi_universal/binaryTM.ma

diff --git a/matita/matita/lib/turing/multi_universal/binaryTM.ma b/matita/matita/lib/turing/multi_universal/binaryTM.ma
new file mode 100644
index 000000000..75cd9f49c
--- /dev/null
+++ b/matita/matita/lib/turing/multi_universal/binaryTM.ma
@@ -0,0 +1,120 @@
+(**************************************************************************)
+(*       ___                                                              *)
+(*      ||M||                                                             *)
+(*      ||A||       A project by Andrea Asperti                           *)
+(*      ||T||                                                             *)
+(*      ||I||       Developers:                                           *)
+(*      ||T||         The HELM team.                                      *)
+(*      ||A||         http://helm.cs.unibo.it                             *)
+(*      \   /                                                             *)
+(*       \ /        This file is distributed under the terms of the       *)
+(*        v         GNU General Public License Version 2                  *)
+(*                                                                        *)
+(**************************************************************************)
+
+include "turing/mono.ma".
+
+(* given a FinSet F:
+   - get its cardinality
+   - return its nth element
+   - return the index of a given element
+ *)
+axiom FS_crd : FinSet → nat.
+axiom FS_nth : ∀F:FinSet.nat → option F.
+axiom index_of_FS : ∀F:FinSet.F → nat.
+
+(* unary bit representation (with a given length) of a certain number *)
+axiom unary_of_nat : nat → nat → nat.
+
+axiom FinVector : Type[0] → nat → FinSet.
+
+definition binary_base_states ≝ initN 7.
+
+definition bin0 : binary_base_states ≝ mk_Sig ?? 0 (leb_true_to_le 1 7 (refl …)).
+definition bin1 : binary_base_states ≝ mk_Sig ?? 1 (leb_true_to_le 2 7 (refl …)).
+definition bin2 : binary_base_states ≝ mk_Sig ?? 2 (leb_true_to_le 3 7 (refl …)).
+definition bin3 : binary_base_states ≝ mk_Sig ?? 3 (leb_true_to_le 4 7 (refl …)).
+definition bin4 : binary_base_states ≝ mk_Sig ?? 4 (leb_true_to_le 5 7 (refl …)).
+definition bin5 : binary_base_states ≝ mk_Sig ?? 5 (leb_true_to_le 6 7 (refl …)).
+definition bin6 : binary_base_states ≝ mk_Sig ?? 6 (leb_true_to_le 7 7 (refl …)).
+
+definition states_binaryTM : FinSet → FinSet → FinSet ≝ λsig,states.
+ FinProd (FinProd states binary_base_states) 
+         (FinProd (FinOption sig) (initN (2 * (FS_crd sig)))).
+
+axiom daemon : ∀T:Type[0].T.
+
+(* controllare i contatori, molti andranno incrementati di uno *)
+definition trans_binaryTM : ∀sig,states:FinSet.
+  (states × (option sig) → states × (option sig) × move) → 
+  ((states_binaryTM sig states) × (option bool) → 
+   (states_binaryTM sig states) × (option bool) × move) 
+≝ λsig,states,trans,p.
+  let 〈s,a〉 ≝ p in
+  let 〈s0,phase,ch,count〉 ≝ s in
+  match pi1 … phase with
+  [ O ⇒ (*** PHASE 0: read ***)
+      match a with
+      [ Some a0 ⇒ 
+        match count with
+        [ O ⇒ 〈〈s0,1,ch,FS_crd sig〉,None ?,N〉
+        | S k ⇒ if (a0 == true) 
+                then 〈〈s0,0,FS_nth sig k,k〉, None ?,R〉
+                else 〈〈s0,0,ch,k〉,None ?,R〉 ]
+      | None ⇒ (* Overflow position! *)
+          〈〈s0,4,None ?,0〉,None ?,R〉 ]
+  | S phase ⇒ match phase with
+  [ O ⇒ (*** PHASE 1: restart ***)
+      match count with
+      [ O ⇒ 〈〈s0,2,ch,FS_crd sig〉,None ?,N〉
+      | S k ⇒ 〈〈s0,1,ch,k〉,None ?,L〉 ]
+  | S phase ⇒ match phase with
+  [ O ⇒ (*** PHASE 2: write ***)
+      let 〈s',a',mv〉 ≝ trans 〈s0,ch〉 in
+      match count with
+      [ O ⇒ let mv' ≝ match mv with [ R ⇒ N | _ ⇒ L ] in
+            let count' ≝ match mv with [ R ⇒ 0 | N ⇒ FS_crd sig | L ⇒ 2*(FS_crd sig) ] in
+             〈〈s',3,ch,count'〉,None ?,mv'〉
+      | S k ⇒ match a' with
+         [ None ⇒ 〈〈s0,2,ch,k〉,None ?,R〉
+         | Some a0' ⇒ let out ≝ (FS_nth k == a') in
+                      〈〈s0,2,ch,k〉,Some ? out,R〉 ]
+      ]
+  | S phase ⇒ match phase with
+  [ O ⇒ (*** PHASE 3: move head left ***)
+      match count with
+      [ O ⇒ 〈〈s0,6,ch,O〉, None ?,N〉
+      | S k ⇒ 〈〈s0,3,ch,k〉, None ?,L〉 ]
+  | S phase ⇒ match phase with
+  [ O ⇒ (*** PHASE 4: check position ***)
+      match a with
+      [ None ⇒ (* niltape/rightof: we can write *) 〈〈s0,2,ch,FS_crd sig〉,None ?,N〉
+      | Some _ ⇒ (* leftof *)
+        let 〈s',a',mv〉 ≝ trans 〈s0,ch〉 in
+        match a' with
+        [ None ⇒ (* we don't write anything: go to end of 2 *) 〈〈s0,2,ch,0〉,None ?,N〉
+        | Some _ ⇒ (* extend tape *) 〈〈s0,5,ch,FS_crd sig〉,None ?,L〉 ]
+      ]
+  | S phase ⇒ match phase with
+  [ O ⇒ (*** PHASE 5: left extension ***)
+      match count with
+      [ O ⇒ 〈〈s0,2,ch,FS_crd sig〉,None ?,N〉
+      | S k ⇒ 〈〈s0,5,ch,k〉,Some ? false,L〉 ]
+  | S _ ⇒ (*** PHASE 6: stop ***) 〈s,None ?,N〉 ]]]]]].  
+
+(*
+ * Una mk_binaryTM prende in input una macchina M e produce una macchina che:
+ * - ha per alfabeto FinBool
+ * - ha stati di tipo (states … M) × (initN 3) × (initN (dimensione dell'alfabeto di M))
+ *   dove il primo elemento corrisponde allo stato della macchina input,
+ *   il secondo identifica la fase (lettura, scrittura, spostamento)
+ *   il terzo è un contatore
+ * - (la funzione di transizione è complessa al punto di rendere discutibile 
+ *)
+definition mk_binaryTM ≝ 
+  λsig.λM:TM sig.mk_TM FinBool (FinProd (states … M) (FinProd (initN 3) (initN
+{ no_states : nat;
+  pos_no_states : (0 < no_states); 
+  ntrans : trans_source no_states → trans_target no_states;
+  nhalt : initN no_states → bool
+}.
\ No newline at end of file
-- 
2.39.2