Theory Reduction

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theory Reduction
imports Residuals
begin

(*  Title:      Reduction.thy
    ID:         $Id: Reduction.thy,v 1.11 2007/10/07 13:49:26 wenzelm Exp $
    Author:     Ole Rasmussen
    Copyright   1995  University of Cambridge
    Logic Image: ZF
*)

theory Reduction imports Residuals begin

(**** Lambda-terms ****)

consts
  lambda        :: "i"
  unmark        :: "i=>i"

abbreviation
  Apl :: "[i,i]=>i" where
  "Apl(n,m) == App(0,n,m)"
  
inductive
  domains       "lambda" <= redexes
  intros
    Lambda_Var:  "               n ∈ nat ==>     Var(n) ∈ lambda"
    Lambda_Fun:  "            u ∈ lambda ==>     Fun(u) ∈ lambda"
    Lambda_App:  "[|u ∈ lambda; v ∈ lambda|] ==> Apl(u,v) ∈ lambda"
  type_intros    redexes.intros bool_typechecks

declare lambda.intros [intro]

primrec
  "unmark(Var(n)) = Var(n)"
  "unmark(Fun(u)) = Fun(unmark(u))"
  "unmark(App(b,f,a)) = Apl(unmark(f), unmark(a))"


declare lambda.intros [simp] 
declare lambda.dom_subset [THEN subsetD, simp, intro]


(* ------------------------------------------------------------------------- *)
(*        unmark lemmas                                                      *)
(* ------------------------------------------------------------------------- *)

lemma unmark_type [intro, simp]:
     "u ∈ redexes ==> unmark(u) ∈ lambda"
by (erule redexes.induct, simp_all)

lemma lambda_unmark: "u ∈ lambda ==> unmark(u) = u"
by (erule lambda.induct, simp_all)


(* ------------------------------------------------------------------------- *)
(*         lift and subst preserve lambda                                    *)
(* ------------------------------------------------------------------------- *)

lemma liftL_type [rule_format]:
     "v ∈ lambda ==> ∀k ∈ nat. lift_rec(v,k) ∈ lambda"
by (erule lambda.induct, simp_all add: lift_rec_Var)

lemma substL_type [rule_format, simp]:
     "v ∈ lambda ==>  ∀n ∈ nat. ∀u ∈ lambda. subst_rec(u,v,n) ∈ lambda"
by (erule lambda.induct, simp_all add: liftL_type subst_Var)


(* ------------------------------------------------------------------------- *)
(*        type-rule for reduction definitions                               *)
(* ------------------------------------------------------------------------- *)

lemmas red_typechecks = substL_type nat_typechecks lambda.intros 
                        bool_typechecks

consts
  Sred1     :: "i"
  Sred      :: "i"
  Spar_red1 :: "i"
  Spar_red  :: "i"

abbreviation
  Sred1_rel (infixl "-1->" 50) where
  "a -1-> b == <a,b> ∈ Sred1"

abbreviation
  Sred_rel (infixl "--->" 50) where
  "a ---> b == <a,b> ∈ Sred"

abbreviation
  Spar_red1_rel (infixl "=1=>" 50) where
  "a =1=> b == <a,b> ∈ Spar_red1"

abbreviation
  Spar_red_rel (infixl "===>" 50) where
  "a ===> b == <a,b> ∈ Spar_red"
  
  
inductive
  domains       "Sred1" <= "lambda*lambda"
  intros
    beta:       "[|m ∈ lambda; n ∈ lambda|] ==> Apl(Fun(m),n) -1-> n/m"
    rfun:       "[|m -1-> n|] ==> Fun(m) -1-> Fun(n)"
    apl_l:      "[|m2 ∈ lambda; m1 -1-> n1|] ==> Apl(m1,m2) -1-> Apl(n1,m2)"
    apl_r:      "[|m1 ∈ lambda; m2 -1-> n2|] ==> Apl(m1,m2) -1-> Apl(m1,n2)"
  type_intros    red_typechecks

declare Sred1.intros [intro, simp]

inductive
  domains       "Sred" <= "lambda*lambda"
  intros
    one_step:   "m-1->n ==> m--->n"
    refl:       "m ∈ lambda==>m --->m"
    trans:      "[|m--->n; n--->p|] ==>m--->p"
  type_intros    Sred1.dom_subset [THEN subsetD] red_typechecks

declare Sred.one_step [intro, simp]
declare Sred.refl     [intro, simp]

inductive
  domains       "Spar_red1" <= "lambda*lambda"
  intros
    beta:       "[|m =1=> m'; n =1=> n'|] ==> Apl(Fun(m),n) =1=> n'/m'"
    rvar:       "n ∈ nat ==> Var(n) =1=> Var(n)"
    rfun:       "m =1=> m' ==> Fun(m) =1=> Fun(m')"
    rapl:       "[|m =1=> m'; n =1=> n'|] ==> Apl(m,n) =1=> Apl(m',n')"
  type_intros    red_typechecks

declare Spar_red1.intros [intro, simp]

inductive
  domains "Spar_red" <= "lambda*lambda"
  intros
    one_step:   "m =1=> n ==> m ===> n"
    trans:      "[|m===>n; n===>p|] ==> m===>p"
  type_intros    Spar_red1.dom_subset [THEN subsetD] red_typechecks

declare Spar_red.one_step [intro, simp]



(* ------------------------------------------------------------------------- *)
(*     Setting up rule lists for reduction                                   *)
(* ------------------------------------------------------------------------- *)

lemmas red1D1 [simp] = Sred1.dom_subset [THEN subsetD, THEN SigmaD1]
lemmas red1D2 [simp] = Sred1.dom_subset [THEN subsetD, THEN SigmaD2]
lemmas redD1 [simp] = Sred.dom_subset [THEN subsetD, THEN SigmaD1]
lemmas redD2 [simp] = Sred.dom_subset [THEN subsetD, THEN SigmaD2]

lemmas par_red1D1 [simp] = Spar_red1.dom_subset [THEN subsetD, THEN SigmaD1]
lemmas par_red1D2 [simp] = Spar_red1.dom_subset [THEN subsetD, THEN SigmaD2]
lemmas par_redD1 [simp] = Spar_red.dom_subset [THEN subsetD, THEN SigmaD1]
lemmas par_redD2 [simp] = Spar_red.dom_subset [THEN subsetD, THEN SigmaD2]

declare bool_typechecks [intro]

inductive_cases  [elim!]: "Fun(t) =1=> Fun(u)"



(* ------------------------------------------------------------------------- *)
(*     Lemmas for reduction                                                  *)
(* ------------------------------------------------------------------------- *)

lemma red_Fun: "m--->n ==> Fun(m) ---> Fun(n)"
apply (erule Sred.induct)
apply (rule_tac [3] Sred.trans, simp_all)
done

lemma red_Apll: "[|n ∈ lambda; m ---> m'|] ==> Apl(m,n)--->Apl(m',n)"
apply (erule Sred.induct)
apply (rule_tac [3] Sred.trans, simp_all)
done

lemma red_Aplr: "[|n ∈ lambda; m ---> m'|] ==> Apl(n,m)--->Apl(n,m')"
apply (erule Sred.induct)
apply (rule_tac [3] Sred.trans, simp_all)
done

lemma red_Apl: "[|m ---> m'; n--->n'|] ==> Apl(m,n)--->Apl(m',n')"
apply (rule_tac n = "Apl (m',n) " in Sred.trans)
apply (simp_all add: red_Apll red_Aplr)
done

lemma red_beta: "[|m ∈ lambda; m':lambda; n ∈ lambda; n':lambda; m ---> m'; n--->n'|] ==>  
               Apl(Fun(m),n)---> n'/m'"
apply (rule_tac n = "Apl (Fun (m'),n') " in Sred.trans)
apply (simp_all add: red_Apl red_Fun)
done


(* ------------------------------------------------------------------------- *)
(*      Lemmas for parallel reduction                                        *)
(* ------------------------------------------------------------------------- *)


lemma refl_par_red1: "m ∈ lambda==> m =1=> m"
by (erule lambda.induct, simp_all)

lemma red1_par_red1: "m-1->n ==> m=1=>n"
by (erule Sred1.induct, simp_all add: refl_par_red1)

lemma red_par_red: "m--->n ==> m===>n"
apply (erule Sred.induct)
apply (rule_tac [3] Spar_red.trans)
apply (simp_all add: refl_par_red1 red1_par_red1)
done

lemma par_red_red: "m===>n ==> m--->n"
apply (erule Spar_red.induct)
apply (erule Spar_red1.induct)
apply (rule_tac [5] Sred.trans)
apply (simp_all add: red_Fun red_beta red_Apl)
done


(* ------------------------------------------------------------------------- *)
(*      Simulation                                                           *)
(* ------------------------------------------------------------------------- *)

lemma simulation: "m=1=>n ==> ∃v. m|>v = n & m~v & regular(v)"
by (erule Spar_red1.induct, force+)


(* ------------------------------------------------------------------------- *)
(*           commuting of unmark and subst                                   *)
(* ------------------------------------------------------------------------- *)

lemma unmmark_lift_rec:
     "u ∈ redexes ==> ∀k ∈ nat. unmark(lift_rec(u,k)) = lift_rec(unmark(u),k)"
by (erule redexes.induct, simp_all add: lift_rec_Var)

lemma unmmark_subst_rec:
 "v ∈ redexes ==> ∀k ∈ nat. ∀u ∈ redexes.   
                  unmark(subst_rec(u,v,k)) = subst_rec(unmark(u),unmark(v),k)"
by (erule redexes.induct, simp_all add: unmmark_lift_rec subst_Var)


(* ------------------------------------------------------------------------- *)
(*        Completeness                                                       *)
(* ------------------------------------------------------------------------- *)

lemma completeness_l [rule_format]:
     "u~v ==> regular(v) --> unmark(u) =1=> unmark(u|>v)"
apply (erule Scomp.induct)
apply (auto simp add: unmmark_subst_rec)
done

lemma completeness: "[|u ∈ lambda; u~v; regular(v)|] ==> u =1=> unmark(u|>v)"
by (drule completeness_l, simp_all add: lambda_unmark)

end


lemma unmark_type:

  u ∈ redexes ==> unmark(u) ∈ lambda

lemma lambda_unmark:

  u ∈ lambda ==> unmark(u) = u

lemma liftL_type:

  [| v ∈ lambda; knat |] ==> lift_rec(v, k) ∈ lambda

lemma substL_type:

  [| v ∈ lambda; nnat; u ∈ lambda |] ==> subst_rec(u, v, n) ∈ lambda

lemma red_typechecks:

  [| v ∈ lambda; nnat; u ∈ lambda |] ==> subst_rec(u, v, n) ∈ lambda
  [| nnat; aC(0); !!m z. [| mnat; zC(m) |] ==> b(m, z) ∈ C(succ(m)) |]
  ==> rec(n, a, b) ∈ C(n)
  0 ∈ nat
  1nat
  nnat ==> succ(n) ∈ nat
  Ord(nat)
  nnat ==> Var(n) ∈ lambda
  u ∈ lambda ==> Fun(u) ∈ lambda
  [| u ∈ lambda; v ∈ lambda |] ==> Apl(u, v) ∈ lambda
  1bool
  0 ∈ bool
  [| bbool; cA(1); dA(0) |] ==> cond(b, c, d) ∈ A(b)
  abool ==> not(a) ∈ bool
  [| abool; bbool |] ==> a and bbool
  [| abool; bbool |] ==> a or bbool
  [| abool; bbool |] ==> a xor bbool

lemma red1D1:

  a -1-> b ==> a ∈ lambda

lemma red1D2:

  a -1-> b ==> b ∈ lambda

lemma redD1:

  a ---> b ==> a ∈ lambda

lemma redD2:

  a ---> b ==> b ∈ lambda

lemma par_red1D1:

  a =1=> b ==> a ∈ lambda

lemma par_red1D2:

  a =1=> b ==> b ∈ lambda

lemma par_redD1:

  a ===> b ==> a ∈ lambda

lemma par_redD2:

  a ===> b ==> b ∈ lambda

lemma red_Fun:

  m ---> n ==> Fun(m) ---> Fun(n)

lemma red_Apll:

  [| n ∈ lambda; m ---> m' |] ==> Apl(m, n) ---> Apl(m', n)

lemma red_Aplr:

  [| n ∈ lambda; m ---> m' |] ==> Apl(n, m) ---> Apl(n, m')

lemma red_Apl:

  [| m ---> m'; n ---> n' |] ==> Apl(m, n) ---> Apl(m', n')

lemma red_beta:

  [| m ∈ lambda; m' ∈ lambda; n ∈ lambda; n' ∈ lambda; m ---> m'; n ---> n' |]
  ==> Apl(Fun(m), n) ---> n' / m'

lemma refl_par_red1:

  m ∈ lambda ==> m =1=> m

lemma red1_par_red1:

  m -1-> n ==> m =1=> n

lemma red_par_red:

  m ---> n ==> m ===> n

lemma par_red_red:

  m ===> n ==> m ---> n

lemma simulation:

  m =1=> n ==> ∃v. m |> v = nm ~ vregular(v)

lemma unmmark_lift_rec:

  u ∈ redexes ==> ∀knat. unmark(lift_rec(u, k)) = lift_rec(unmark(u), k)

lemma unmmark_subst_rec:

  v ∈ redexes
  ==> ∀knat.
         ∀u∈redexes.
            unmark(subst_rec(u, v, k)) = subst_rec(unmark(u), unmark(v), k)

lemma completeness_l:

  [| u ~ v; regular(v) |] ==> unmark(u) =1=> unmark(u |> v)

lemma completeness:

  [| u ∈ lambda; u ~ v; regular(v) |] ==> u =1=> unmark(u |> v)