# Theory Example

theory Example
imports Equivalence
(*  Title:      HOL/NanoJava/Example.thy
Author:     David von Oheimb
*)

section "Example"

theory Example
imports Equivalence
begin

text ‹

\begin{verbatim}
class Nat {

Nat pred;

Nat suc()
{ Nat n = new Nat(); n.pred = this; return n; }

Nat eq(Nat n)
{ if (this.pred != null) if (n.pred != null) return this.pred.eq(n.pred);
else return n.pred; // false
else if (n.pred != null) return this.pred; // false
else return this.suc(); // true
}

{ if (this.pred != null) return this.pred.add(n.suc()); else return n; }

public static void main(String[] args) // test x+1=1+x
{
Nat one = new Nat().suc();
Nat x   = new Nat().suc().suc().suc().suc();
System.out.println(ok != null);
}
}
\end{verbatim}

›

axiomatization where
This_neq_Par [simp]: "This ≠ Par" and
Res_neq_This [simp]: "Res  ≠ This"

subsection "Program representation"

axiomatization
N    :: cname ("Nat") (* with mixfix because of clash with NatDef.Nat *)
and pred :: fname
and any  :: vname

abbreviation
dummy :: expr ("<>")
where "<> == LAcc any"

abbreviation
one :: expr
where "one == {Nat}new Nat..suc(<>)"

text ‹The following properties could be derived from a more complete
program model, which we leave out for laziness.›

axiomatization where Nat_no_subclasses [simp]: "D ≼C Nat = (D=Nat)"

⦇ par=Class Nat, res=Class Nat, lcl=[],
bdy= If((LAcc This..pred))
Else Res :== LAcc Par ⦈"

axiomatization where method_Nat_suc [simp]: "method Nat suc = Some
⦇ par=NT, res=Class Nat, lcl=[],
bdy= Res :== new Nat;; LAcc Res..pred :== LAcc This ⦈"

axiomatization where field_Nat [simp]: "field Nat = empty(pred↦Class Nat)"

lemma init_locs_Nat_suc [simp]: "init_locs Nat suc s = s"

lemma upd_obj_new_obj_Nat [simp]:
"upd_obj a pred v (new_obj a Nat s) = hupd(a↦(Nat, empty(pred↦v))) s"
by (simp add: new_obj_def init_vars_def upd_obj_def Let_def)

subsection "atleast'' relation for interpretation of Nat values''"

primrec Nat_atleast :: "state ⇒ val ⇒ nat ⇒ bool" ("_:_ ≥ _" [51, 51, 51] 50) where
"s:x≥0     = (x≠Null)"
| "s:x≥Suc n = (∃a. x=Addr a ∧ heap s a ≠ None ∧ s:get_field s a pred≥n)"

lemma Nat_atleast_lupd [rule_format, simp]:
"∀s v::val. lupd(x↦y) s:v ≥ n = (s:v ≥ n)"
apply (induct n)
by  auto

lemma Nat_atleast_set_locs [rule_format, simp]:
"∀s v::val. set_locs l s:v ≥ n = (s:v ≥ n)"
apply (induct n)
by auto

lemma Nat_atleast_del_locs [rule_format, simp]:
"∀s v::val. del_locs s:v ≥ n = (s:v ≥ n)"
apply (induct n)
by auto

lemma Nat_atleast_NullD [rule_format]: "s:Null ≥ n ⟶ False"
apply (induct n)
by auto

lemma Nat_atleast_pred_NullD [rule_format]:
"Null = get_field s a pred ⟹ s:Addr a ≥ n ⟶ n = 0"
apply (induct n)
by (auto dest: Nat_atleast_NullD)

lemma Nat_atleast_mono [rule_format]:
"∀a. s:get_field s a pred ≥ n ⟶ heap s a ≠ None ⟶ s:Addr a ≥ n"
apply (induct n)
by auto

lemma Nat_atleast_newC [rule_format]:
"heap s aa = None ⟹ ∀v::val. s:v ≥ n ⟶ hupd(aa↦obj) s:v ≥ n"
apply (induct n)
apply  auto
apply  (case_tac "aa=a")
apply   auto
apply (tactic "smp_tac @{context} 1 1")
apply (case_tac "aa=a")
apply  auto
done

subsection "Proof(s) using the Hoare logic"

"{} ⊢ {λs. s:s<This> ≥ X ∧ s:s<Par> ≥ Y} Meth(Nat,add) {λs. s:s<Res> ≥ X+Y}"
apply (rule hoare_ehoare.Meth) (* 1 *)
apply clarsimp
apply (rule_tac P'= "λZ s. (s:s<This> ≥ fst Z ∧ s:s<Par> ≥ snd Z) ∧ D=Nat" and
Q'= "λZ s. s:s<Res> ≥ fst Z+snd Z" in AxSem.Conseq)
prefer 2
apply  (clarsimp simp add: init_locs_def init_vars_def)
apply rule
apply (case_tac "D = Nat", simp_all, rule_tac [2] cFalse)
apply (rule_tac P = "λZ Cm s. s:s<This> ≥ fst Z ∧ s:s<Par> ≥ snd Z" in AxSem.Impl1)
apply (clarsimp simp add: body_def)  (* 4 *)
apply (rename_tac n m)
apply (rule_tac Q = "λv s. (s:s<This> ≥ n ∧ s:s<Par> ≥ m) ∧
(∃a. s<This> = Addr a ∧ v = get_field s a pred)" in hoare_ehoare.Cond)
apply  (rule hoare_ehoare.FAcc)
apply  (rule eConseq1)
apply   (rule hoare_ehoare.LAcc)
apply  fast
apply auto
prefer 2
apply  (rule hoare_ehoare.LAss)
apply  (rule eConseq1)
apply   (rule hoare_ehoare.LAcc)
apply  (auto dest: Nat_atleast_pred_NullD)
apply (rule hoare_ehoare.LAss)
apply (rule_tac
Q = "λv   s. (∀m. n = Suc m ⟶ s:v ≥ m) ∧ s:s<Par> ≥ m" and
R = "λT P s. (∀m. n = Suc m ⟶ s:T ≥ m) ∧ s:P  ≥ Suc m"
in hoare_ehoare.Call) (* 13 *)
apply   (rule hoare_ehoare.FAcc)
apply   (rule eConseq1)
apply    (rule hoare_ehoare.LAcc)
apply   clarify
apply   (drule sym, rotate_tac -1, frule (1) trans)
apply   simp
prefer 2
apply  clarsimp
apply  (rule hoare_ehoare.Meth) (* 17 *)
apply  clarsimp
apply  (case_tac "D = Nat", simp_all, rule_tac [2] cFalse)
apply  (rule AxSem.Conseq)
apply   rule
apply   (rule hoare_ehoare.Asm) (* 20 *)
apply   (rule_tac a = "((case n of 0 ⇒ 0 | Suc m ⇒ m),m+1)" in UN_I, rule+)
apply  (clarsimp split: nat.split_asm dest!: Nat_atleast_mono)
apply rule
apply (rule hoare_ehoare.Call) (* 21 *)
apply   (rule hoare_ehoare.LAcc)
apply  rule
apply  (rule hoare_ehoare.LAcc)
apply clarify
apply (rule hoare_ehoare.Meth) (* 24 *)
apply clarsimp
apply  (case_tac "D = Nat", simp_all, rule_tac [2] cFalse)
apply (rule AxSem.Impl1)
apply (rule hoare_ehoare.Comp) (* 26 *)
prefer 2
apply  (rule hoare_ehoare.FAss)
prefer 2
apply   rule
apply   (rule hoare_ehoare.LAcc)
apply  (rule hoare_ehoare.LAcc)
apply (rule hoare_ehoare.LAss)
apply (rule eConseq1)
apply  (rule hoare_ehoare.NewC) (* 32 *)
apply (auto dest!: new_AddrD elim: Nat_atleast_newC)
done

end