Theory State

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theory State
imports Main
begin

(*  Title:      HOL/UNITY/State.thy
    ID:         $Id: State.thy,v 1.8 2007/10/07 19:19:35 wenzelm Exp $
    Author:     Sidi O Ehmety, Computer Laboratory
    Copyright   2001  University of Cambridge

Formalizes UNITY-program states using dependent types so that:
 - variables are typed.
 - the state space is uniform, common to all defined programs.
 - variables can be quantified over.
*)

header{*UNITY Program States*}

theory State imports Main begin

consts var :: i
datatype var = Var("i ∈ list(nat)")
  type_intros  nat_subset_univ [THEN list_subset_univ, THEN subsetD]

consts
  type_of :: "i=>i"
  default_val :: "i=>i"

definition
  "state == Π x ∈ var. cons(default_val(x), type_of(x))"

definition
  "st0 == λx ∈ var. default_val(x)"
  
definition
  st_set  :: "i=>o"  where
(* To prevent typing conditions like `A<=state' from
   being used in combination with the rules `constrains_weaken', etc. *)
  "st_set(A) == A<=state"

definition
  st_compl :: "i=>i"  where
  "st_compl(A) == state-A"


lemma st0_in_state [simp,TC]: "st0 ∈ state"
by (simp add: state_def st0_def)

lemma st_set_Collect [iff]: "st_set({x ∈ state. P(x)})"
by (simp add: st_set_def, auto)

lemma st_set_0 [iff]: "st_set(0)"
by (simp add: st_set_def)

lemma st_set_state [iff]: "st_set(state)"
by (simp add: st_set_def)

(* Union *)

lemma st_set_Un_iff [iff]: "st_set(A Un B) <-> st_set(A) & st_set(B)"
by (simp add: st_set_def, auto)

lemma st_set_Union_iff [iff]: "st_set(Union(S)) <-> (∀A ∈ S. st_set(A))"
by (simp add: st_set_def, auto)

(* Intersection *)

lemma st_set_Int [intro!]: "st_set(A) | st_set(B) ==> st_set(A Int B)"
by (simp add: st_set_def, auto)

lemma st_set_Inter [intro!]: 
   "(S=0) | (∃A ∈ S. st_set(A)) ==> st_set(Inter(S))"
apply (simp add: st_set_def Inter_def, auto)
done

(* Diff *)
lemma st_set_DiffI [intro!]: "st_set(A) ==> st_set(A - B)"
by (simp add: st_set_def, auto)

lemma Collect_Int_state [simp]: "Collect(state,P) Int state = Collect(state,P)"
by auto

lemma state_Int_Collect [simp]: "state Int Collect(state,P) = Collect(state,P)"
by auto


(* Introduction and destruction rules for st_set *)

lemma st_setI: "A <= state ==> st_set(A)"
by (simp add: st_set_def)

lemma st_setD: "st_set(A) ==> A<=state"
by (simp add: st_set_def)

lemma st_set_subset: "[| st_set(A); B<=A |] ==> st_set(B)"
by (simp add: st_set_def, auto)


lemma state_update_type: 
     "[| s ∈ state; x ∈ var; y ∈ type_of(x) |] ==> s(x:=y):state"
apply (simp add: state_def)
apply (blast intro: update_type)
done

lemma st_set_compl [simp]: "st_set(st_compl(A))"
by (simp add: st_compl_def, auto)

lemma st_compl_iff [simp]: "x ∈ st_compl(A) <-> x ∈ state & x ∉ A"
by (simp add: st_compl_def)

lemma st_compl_Collect [simp]:
     "st_compl({s ∈ state. P(s)}) = {s ∈ state. ~P(s)}"
by (simp add: st_compl_def, auto)

(*For using "disjunction" (union over an index set) to eliminate a variable.*)
lemma UN_conj_eq:
     "∀d∈D. f(d) ∈ A ==> (\<Union>k∈A. {d∈D. P(d) & f(d) = k}) = {d∈D. P(d)}"
by blast

end

lemma st0_in_state:

  st0state

lemma st_set_Collect:

  st_set({xstate . P(x)})

lemma st_set_0:

  st_set(0)

lemma st_set_state:

  st_set(state)

lemma st_set_Un_iff:

  st_set(AB) <-> st_set(A) ∧ st_set(B)

lemma st_set_Union_iff:

  st_set(\<Union>S) <-> (∀AS. st_set(A))

lemma st_set_Int:

  st_set(A) ∨ st_set(B) ==> st_set(AB)

lemma st_set_Inter:

  S = 0 ∨ (∃AS. st_set(A)) ==> st_set(\<Inter>S)

lemma st_set_DiffI:

  st_set(A) ==> st_set(A - B)

lemma Collect_Int_state:

  Collect(state, P) ∩ state = Collect(state, P)

lemma state_Int_Collect:

  state ∩ Collect(state, P) = Collect(state, P)

lemma st_setI:

  Astate ==> st_set(A)

lemma st_setD:

  st_set(A) ==> Astate

lemma st_set_subset:

  [| st_set(A); BA |] ==> st_set(B)

lemma state_update_type:

  [| sstate; x ∈ var; y ∈ type_of(x) |] ==> s(x := y) ∈ state

lemma st_set_compl:

  st_set(st_compl(A))

lemma st_compl_iff:

  xst_compl(A) <-> xstatex  A

lemma st_compl_Collect:

  st_compl({sstate . P(s)}) = {sstate . ¬ P(s)}

lemma UN_conj_eq:

  dD. f(d) ∈ A ==> (\<Union>kA. {dD . P(d) ∧ f(d) = k}) = {dD . P(d)}