author | nipkow |
Sun, 10 Mar 2013 18:29:10 +0100 | |
changeset 51389 | 8a9f0503b1c0 |
parent 51359 | 00b45c7e831f |
child 51390 | 1dff81cf425b |
permissions | -rw-r--r-- |
47613 | 1 |
(* Author: Tobias Nipkow *) |
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theory Abs_Int0 |
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imports Abs_Int_init |
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begin |
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subsection "Orderings" |
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declare order_trans[trans] |
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class semilattice = semilattice_sup + top |
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(* + |
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assumes join_ge1 [simp]: "x \<le> x \<squnion> y" |
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and join_ge2 [simp]: "y \<le> x \<squnion> y" |
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and join_least: "x \<le> z \<Longrightarrow> y \<le> z \<Longrightarrow> x \<squnion> y \<le> z" |
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begin |
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lemma join_le_iff[simp]: "x \<squnion> y \<le> z \<longleftrightarrow> x \<le> z \<and> y \<le> z" |
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by (metis join_ge1 join_ge2 join_least order_trans) |
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*) |
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lemma le_join_disj: "x \<le> y \<or> x \<le> z \<Longrightarrow> x \<le> y \<squnion> (z::'a::semilattice_sup)" |
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by (metis sup_ge1 sup_ge2 order_trans) |
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instance "fun" :: (type, semilattice) semilattice .. |
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(* |
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definition top_fun where "top_fun = (\<lambda>x. \<top>)" |
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lemma join_apply[simp]: "(f \<squnion> g) x = f x \<squnion> g x" |
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by (simp add: join_fun_def) |
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instance |
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proof |
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qed (simp_all add: le_fun_def) |
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end |
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*) |
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instantiation option :: (order)order |
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begin |
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fun less_eq_option where |
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"Some x \<le> Some y = (x \<le> y)" | |
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"None \<le> y = True" | |
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"Some _ \<le> None = False" |
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definition less_option where "x < (y::'a option) = (x \<le> y \<and> \<not> y \<le> x)" |
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lemma [simp]: "(x \<le> None) = (x = None)" |
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by (cases x) simp_all |
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lemma [simp]: "(Some x \<le> u) = (\<exists>y. u = Some y \<and> x \<le> y)" |
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by (cases u) auto |
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instance proof |
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case goal1 show ?case by(rule less_option_def) |
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next |
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case goal2 show ?case by(cases x, simp_all) |
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next |
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case goal3 thus ?case by(cases z, simp, cases y, simp, cases x, auto) |
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next |
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case goal4 thus ?case by(cases y, simp, cases x, auto) |
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qed |
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end |
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instantiation option :: (sup)sup |
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begin |
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fun sup_option where |
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"Some x \<squnion> Some y = Some(x \<squnion> y)" | |
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"None \<squnion> y = y" | |
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"x \<squnion> None = x" |
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lemma sup_None2[simp]: "x \<squnion> None = x" |
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by (cases x) simp_all |
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instance .. |
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end |
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instantiation option :: (semilattice)semilattice |
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begin |
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definition top_option where "\<top> = Some \<top>" |
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instance proof |
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case goal4 show ?case by(cases a, simp_all add: top_option_def) |
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next |
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case goal1 thus ?case by(cases x, simp, cases y, simp_all) |
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next |
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case goal2 thus ?case by(cases y, simp, cases x, simp_all) |
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next |
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case goal3 thus ?case by(cases z, simp, cases y, simp, cases x, simp_all) |
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qed |
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end |
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instantiation option :: (order)bot |
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begin |
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definition bot_option :: "'a option" where |
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"\<bottom> = None" |
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instance |
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proof |
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case goal1 thus ?case by(auto simp: bot_option_def) |
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qed |
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end |
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definition bot :: "com \<Rightarrow> 'a option acom" where |
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"bot c = anno None c" |
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lemma bot_least: "strip C = c \<Longrightarrow> bot c \<le> C" |
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by(induct C arbitrary: c)(auto simp: bot_def) |
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lemma strip_bot[simp]: "strip(bot c) = c" |
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by(simp add: bot_def) |
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subsubsection "Post-fixed point iteration" |
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definition pfp :: "(('a::order) \<Rightarrow> 'a) \<Rightarrow> 'a \<Rightarrow> 'a option" where |
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"pfp f = while_option (\<lambda>x. \<not> f x \<le> x) f" |
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lemma pfp_pfp: assumes "pfp f x0 = Some x" shows "f x \<le> x" |
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using while_option_stop[OF assms[simplified pfp_def]] by simp |
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lemma while_least: |
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fixes q :: "'a::order" |
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assumes "\<forall>x\<in>L.\<forall>y\<in>L. x \<le> y \<longrightarrow> f x \<le> f y" and "\<forall>x. x \<in> L \<longrightarrow> f x \<in> L" |
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and "\<forall>x \<in> L. b \<le> x" and "b \<in> L" and "f q \<le> q" and "q \<in> L" |
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and "while_option P f b = Some p" |
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shows "p \<le> q" |
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using while_option_rule[OF _ assms(7)[unfolded pfp_def], |
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where P = "%x. x \<in> L \<and> x \<le> q"] |
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by (metis assms(1-6) order_trans) |
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lemma pfp_inv: |
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"pfp f x = Some y \<Longrightarrow> (\<And>x. P x \<Longrightarrow> P(f x)) \<Longrightarrow> P x \<Longrightarrow> P y" |
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unfolding pfp_def by (metis (lifting) while_option_rule) |
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lemma strip_pfp: |
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assumes "\<And>x. g(f x) = g x" and "pfp f x0 = Some x" shows "g x = g x0" |
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using pfp_inv[OF assms(2), where P = "%x. g x = g x0"] assms(1) by simp |
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subsection "Abstract Interpretation" |
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definition \<gamma>_fun :: "('a \<Rightarrow> 'b set) \<Rightarrow> ('c \<Rightarrow> 'a) \<Rightarrow> ('c \<Rightarrow> 'b)set" where |
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"\<gamma>_fun \<gamma> F = {f. \<forall>x. f x \<in> \<gamma>(F x)}" |
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fun \<gamma>_option :: "('a \<Rightarrow> 'b set) \<Rightarrow> 'a option \<Rightarrow> 'b set" where |
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"\<gamma>_option \<gamma> None = {}" | |
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"\<gamma>_option \<gamma> (Some a) = \<gamma> a" |
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text{* The interface for abstract values: *} |
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locale Val_abs = |
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fixes \<gamma> :: "'av::semilattice \<Rightarrow> val set" |
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assumes mono_gamma: "a \<le> b \<Longrightarrow> \<gamma> a \<le> \<gamma> b" |
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and gamma_Top[simp]: "\<gamma> \<top> = UNIV" |
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fixes num' :: "val \<Rightarrow> 'av" |
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and plus' :: "'av \<Rightarrow> 'av \<Rightarrow> 'av" |
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assumes gamma_num': "i \<in> \<gamma>(num' i)" |
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and gamma_plus': "i1 \<in> \<gamma> a1 \<Longrightarrow> i2 \<in> \<gamma> a2 \<Longrightarrow> i1+i2 \<in> \<gamma>(plus' a1 a2)" |
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type_synonym 'av st = "(vname \<Rightarrow> 'av)" |
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locale Abs_Int_Fun = Val_abs \<gamma> for \<gamma> :: "'av::semilattice \<Rightarrow> val set" |
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begin |
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fun aval' :: "aexp \<Rightarrow> 'av st \<Rightarrow> 'av" where |
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"aval' (N i) S = num' i" | |
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"aval' (V x) S = S x" | |
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"aval' (Plus a1 a2) S = plus' (aval' a1 S) (aval' a2 S)" |
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(* Interpretation would be nicer but is impossible *) |
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definition "step' = Step.Step |
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(\<lambda>x e S. case S of None \<Rightarrow> None | Some S \<Rightarrow> Some(S(x := aval' e S))) |
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(\<lambda>b S. S)" |
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lemma [simp]: "step' S (SKIP {P}) = (SKIP {S})" |
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by(simp add: step'_def Step.Step.simps) |
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lemma [simp]: "step' S (x ::= e {P}) = |
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x ::= e {case S of None \<Rightarrow> None | Some S \<Rightarrow> Some(S(x := aval' e S))}" |
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by(simp add: step'_def Step.Step.simps) |
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lemma [simp]: "step' S (C1; C2) = step' S C1; step' (post C1) C2" |
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by(simp add: step'_def Step.Step.simps) |
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lemma [simp]: "step' S (IF b THEN {P1} C1 ELSE {P2} C2 {Q}) = |
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IF b THEN {S} step' P1 C1 ELSE {S} step' P2 C2 |
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{post C1 \<squnion> post C2}" |
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by(simp add: step'_def Step.Step.simps) |
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lemma [simp]: "step' S ({I} WHILE b DO {P} C {Q}) = |
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{S \<squnion> post C} WHILE b DO {I} step' P C {I}" |
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by(simp add: step'_def Step.Step.simps) |
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definition AI :: "com \<Rightarrow> 'av st option acom option" where |
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"AI c = pfp (step' \<top>) (bot c)" |
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lemma strip_step'[simp]: "strip(step' S C) = strip C" |
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by(induct C arbitrary: S) (simp_all add: Let_def) |
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abbreviation \<gamma>\<^isub>s :: "'av st \<Rightarrow> state set" |
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where "\<gamma>\<^isub>s == \<gamma>_fun \<gamma>" |
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abbreviation \<gamma>\<^isub>o :: "'av st option \<Rightarrow> state set" |
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where "\<gamma>\<^isub>o == \<gamma>_option \<gamma>\<^isub>s" |
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abbreviation \<gamma>\<^isub>c :: "'av st option acom \<Rightarrow> state set acom" |
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where "\<gamma>\<^isub>c == map_acom \<gamma>\<^isub>o" |
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lemma gamma_s_Top[simp]: "\<gamma>\<^isub>s \<top> = UNIV" |
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by(simp add: top_fun_def \<gamma>_fun_def) |
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lemma gamma_o_Top[simp]: "\<gamma>\<^isub>o \<top> = UNIV" |
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by (simp add: top_option_def) |
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lemma mono_gamma_s: "f1 \<le> f2 \<Longrightarrow> \<gamma>\<^isub>s f1 \<subseteq> \<gamma>\<^isub>s f2" |
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by(auto simp: le_fun_def \<gamma>_fun_def dest: mono_gamma) |
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lemma mono_gamma_o: |
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"S1 \<le> S2 \<Longrightarrow> \<gamma>\<^isub>o S1 \<subseteq> \<gamma>\<^isub>o S2" |
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by(induction S1 S2 rule: less_eq_option.induct)(simp_all add: mono_gamma_s) |
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lemma mono_gamma_c: "C1 \<le> C2 \<Longrightarrow> \<gamma>\<^isub>c C1 \<le> \<gamma>\<^isub>c C2" |
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by (induction C1 C2 rule: less_eq_acom.induct) (simp_all add:mono_gamma_o) |
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text{* Soundness: *} |
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lemma aval'_sound: "s : \<gamma>\<^isub>s S \<Longrightarrow> aval a s : \<gamma>(aval' a S)" |
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by (induct a) (auto simp: gamma_num' gamma_plus' \<gamma>_fun_def) |
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lemma in_gamma_update: |
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"\<lbrakk> s : \<gamma>\<^isub>s S; i : \<gamma> a \<rbrakk> \<Longrightarrow> s(x := i) : \<gamma>\<^isub>s(S(x := a))" |
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by(simp add: \<gamma>_fun_def) |
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lemma step_step': "step (\<gamma>\<^isub>o S) (\<gamma>\<^isub>c C) \<le> \<gamma>\<^isub>c (step' S C)" |
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proof(induction C arbitrary: S) |
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case SKIP thus ?case by auto |
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next |
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case Assign thus ?case |
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by (fastforce intro: aval'_sound in_gamma_update split: option.splits) |
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next |
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case Seq thus ?case by auto |
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next |
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case If thus ?case by (auto simp: mono_gamma_o) |
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next |
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case While thus ?case by (auto simp: mono_gamma_o) |
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qed |
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lemma AI_sound: "AI c = Some C \<Longrightarrow> CS c \<le> \<gamma>\<^isub>c C" |
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proof(simp add: CS_def AI_def) |
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assume 1: "pfp (step' \<top>) (bot c) = Some C" |
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have pfp': "step' \<top> C \<le> C" by(rule pfp_pfp[OF 1]) |
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have 2: "step (\<gamma>\<^isub>o \<top>) (\<gamma>\<^isub>c C) \<le> \<gamma>\<^isub>c C" --"transfer the pfp'" |
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proof(rule order_trans) |
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show "step (\<gamma>\<^isub>o \<top>) (\<gamma>\<^isub>c C) \<le> \<gamma>\<^isub>c (step' \<top> C)" by(rule step_step') |
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show "... \<le> \<gamma>\<^isub>c C" by (metis mono_gamma_c[OF pfp']) |
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qed |
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have 3: "strip (\<gamma>\<^isub>c C) = c" by(simp add: strip_pfp[OF _ 1]) |
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have "lfp c (step (\<gamma>\<^isub>o \<top>)) \<le> \<gamma>\<^isub>c C" |
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by(rule lfp_lowerbound[simplified,where f="step (\<gamma>\<^isub>o \<top>)", OF 3 2]) |
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thus "lfp c (step UNIV) \<le> \<gamma>\<^isub>c C" by simp |
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qed |
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end |
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subsubsection "Monotonicity" |
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lemma mono_post: "C1 \<le> C2 \<Longrightarrow> post C1 \<le> post C2" |
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by(induction C1 C2 rule: less_eq_acom.induct) (auto) |
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locale Abs_Int_Fun_mono = Abs_Int_Fun + |
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assumes mono_plus': "a1 \<le> b1 \<Longrightarrow> a2 \<le> b2 \<Longrightarrow> plus' a1 a2 \<le> plus' b1 b2" |
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begin |
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lemma mono_aval': "S \<le> S' \<Longrightarrow> aval' e S \<le> aval' e S'" |
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by(induction e)(auto simp: le_fun_def mono_plus') |
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lemma mono_update: "a \<le> a' \<Longrightarrow> S \<le> S' \<Longrightarrow> S(x := a) \<le> S'(x := a')" |
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by(simp add: le_fun_def) |
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lemma mono_step': "S1 \<le> S2 \<Longrightarrow> C1 \<le> C2 \<Longrightarrow> step' S1 C1 \<le> step' S2 C2" |
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apply(induction C1 C2 arbitrary: S1 S2 rule: less_eq_acom.induct) |
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apply (auto simp: Let_def mono_update mono_aval' mono_post le_join_disj |
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split: option.split) |
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done |
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end |
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text{* Problem: not executable because of the comparison of abstract states, |
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i.e. functions, in the post-fixedpoint computation. *} |
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end |