diff --git a/src/HOL/Complete_Partial_Order.thy b/src/HOL/Complete_Partial_Order.thy --- a/src/HOL/Complete_Partial_Order.thy +++ b/src/HOL/Complete_Partial_Order.thy @@ -1,381 +1,372 @@ (* Title: HOL/Complete_Partial_Order.thy Author: Brian Huffman, Portland State University Author: Alexander Krauss, TU Muenchen *) section \Chain-complete partial orders and their fixpoints\ theory Complete_Partial_Order imports Product_Type begin subsection \Monotone functions\ text \Dictionary-passing version of \<^const>\Orderings.mono\.\ definition monotone :: "('a \ 'a \ bool) \ ('b \ 'b \ bool) \ ('a \ 'b) \ bool" where "monotone orda ordb f \ (\x y. orda x y \ ordb (f x) (f y))" lemma monotoneI[intro?]: "(\x y. orda x y \ ordb (f x) (f y)) \ monotone orda ordb f" unfolding monotone_def by iprover lemma monotoneD[dest?]: "monotone orda ordb f \ orda x y \ ordb (f x) (f y)" unfolding monotone_def by iprover subsection \Chains\ text \ A chain is a totally-ordered set. Chains are parameterized over the order for maximal flexibility, since type classes are not enough. \ definition chain :: "('a \ 'a \ bool) \ 'a set \ bool" where "chain ord S \ (\x\S. \y\S. ord x y \ ord y x)" lemma chainI: assumes "\x y. x \ S \ y \ S \ ord x y \ ord y x" shows "chain ord S" using assms unfolding chain_def by fast lemma chainD: assumes "chain ord S" and "x \ S" and "y \ S" shows "ord x y \ ord y x" using assms unfolding chain_def by fast lemma chainE: assumes "chain ord S" and "x \ S" and "y \ S" obtains "ord x y" | "ord y x" using assms unfolding chain_def by fast lemma chain_empty: "chain ord {}" by (simp add: chain_def) lemma chain_equality: "chain (=) A \ (\x\A. \y\A. x = y)" by (auto simp add: chain_def) lemma chain_subset: "chain ord A \ B \ A \ chain ord B" by (rule chainI) (blast dest: chainD) lemma chain_imageI: assumes chain: "chain le_a Y" and mono: "\x y. x \ Y \ y \ Y \ le_a x y \ le_b (f x) (f y)" shows "chain le_b (f ` Y)" by (blast intro: chainI dest: chainD[OF chain] mono) subsection \Chain-complete partial orders\ text \ A \ccpo\ has a least upper bound for any chain. In particular, the empty set is a chain, so every \ccpo\ must have a bottom element. \ class ccpo = order + Sup + assumes ccpo_Sup_upper: "chain (\) A \ x \ A \ x \ Sup A" assumes ccpo_Sup_least: "chain (\) A \ (\x. x \ A \ x \ z) \ Sup A \ z" begin lemma chain_singleton: "Complete_Partial_Order.chain (\) {x}" by (rule chainI) simp lemma ccpo_Sup_singleton [simp]: "\{x} = x" by (rule antisym) (auto intro: ccpo_Sup_least ccpo_Sup_upper simp add: chain_singleton) subsection \Transfinite iteration of a function\ context notes [[inductive_internals]] begin inductive_set iterates :: "('a \ 'a) \ 'a set" for f :: "'a \ 'a" where step: "x \ iterates f \ f x \ iterates f" | Sup: "chain (\) M \ \x\M. x \ iterates f \ Sup M \ iterates f" end lemma iterates_le_f: "x \ iterates f \ monotone (\) (\) f \ x \ f x" by (induct x rule: iterates.induct) (force dest: monotoneD intro!: ccpo_Sup_upper ccpo_Sup_least)+ lemma chain_iterates: assumes f: "monotone (\) (\) f" shows "chain (\) (iterates f)" (is "chain _ ?C") proof (rule chainI) fix x y assume "x \ ?C" "y \ ?C" then show "x \ y \ y \ x" proof (induct x arbitrary: y rule: iterates.induct) fix x y assume y: "y \ ?C" and IH: "\z. z \ ?C \ x \ z \ z \ x" from y show "f x \ y \ y \ f x" proof (induct y rule: iterates.induct) case (step y) with IH f show ?case by (auto dest: monotoneD) next case (Sup M) then have chM: "chain (\) M" and IH': "\z. z \ M \ f x \ z \ z \ f x" by auto show "f x \ Sup M \ Sup M \ f x" proof (cases "\z\M. f x \ z") case True then have "f x \ Sup M" - apply rule - apply (erule order_trans) - apply (rule ccpo_Sup_upper[OF chM]) - apply assumption - done + by (blast intro: ccpo_Sup_upper[OF chM] order_trans) then show ?thesis .. next case False with IH' show ?thesis by (auto intro: ccpo_Sup_least[OF chM]) qed qed next case (Sup M y) show ?case proof (cases "\x\M. y \ x") case True then have "y \ Sup M" - apply rule - apply (erule order_trans) - apply (rule ccpo_Sup_upper[OF Sup(1)]) - apply assumption - done + by (blast intro: ccpo_Sup_upper[OF Sup(1)] order_trans) then show ?thesis .. next case False with Sup show ?thesis by (auto intro: ccpo_Sup_least) qed qed qed lemma bot_in_iterates: "Sup {} \ iterates f" by (auto intro: iterates.Sup simp add: chain_empty) subsection \Fixpoint combinator\ definition fixp :: "('a \ 'a) \ 'a" where "fixp f = Sup (iterates f)" lemma iterates_fixp: assumes f: "monotone (\) (\) f" shows "fixp f \ iterates f" unfolding fixp_def by (simp add: iterates.Sup chain_iterates f) lemma fixp_unfold: assumes f: "monotone (\) (\) f" shows "fixp f = f (fixp f)" proof (rule antisym) show "fixp f \ f (fixp f)" by (intro iterates_le_f iterates_fixp f) have "f (fixp f) \ Sup (iterates f)" by (intro ccpo_Sup_upper chain_iterates f iterates.step iterates_fixp) then show "f (fixp f) \ fixp f" by (simp only: fixp_def) qed lemma fixp_lowerbound: assumes f: "monotone (\) (\) f" and z: "f z \ z" shows "fixp f \ z" unfolding fixp_def proof (rule ccpo_Sup_least[OF chain_iterates[OF f]]) fix x assume "x \ iterates f" then show "x \ z" proof (induct x rule: iterates.induct) case (step x) from f \x \ z\ have "f x \ f z" by (rule monotoneD) also note z finally show "f x \ z" . next case (Sup M) then show ?case by (auto intro: ccpo_Sup_least) qed qed end subsection \Fixpoint induction\ setup \Sign.map_naming (Name_Space.mandatory_path "ccpo")\ definition admissible :: "('a set \ 'a) \ ('a \ 'a \ bool) \ ('a \ bool) \ bool" where "admissible lub ord P \ (\A. chain ord A \ A \ {} \ (\x\A. P x) \ P (lub A))" lemma admissibleI: assumes "\A. chain ord A \ A \ {} \ \x\A. P x \ P (lub A)" shows "ccpo.admissible lub ord P" using assms unfolding ccpo.admissible_def by fast lemma admissibleD: assumes "ccpo.admissible lub ord P" assumes "chain ord A" assumes "A \ {}" assumes "\x. x \ A \ P x" shows "P (lub A)" using assms by (auto simp: ccpo.admissible_def) setup \Sign.map_naming Name_Space.parent_path\ lemma (in ccpo) fixp_induct: assumes adm: "ccpo.admissible Sup (\) P" assumes mono: "monotone (\) (\) f" assumes bot: "P (Sup {})" assumes step: "\x. P x \ P (f x)" shows "P (fixp f)" unfolding fixp_def using adm chain_iterates[OF mono] proof (rule ccpo.admissibleD) show "iterates f \ {}" using bot_in_iterates by auto next fix x assume "x \ iterates f" then show "P x" proof (induct rule: iterates.induct) case prems: (step x) from this(2) show ?case by (rule step) next case (Sup M) then show ?case by (cases "M = {}") (auto intro: step bot ccpo.admissibleD adm) qed qed lemma admissible_True: "ccpo.admissible lub ord (\x. True)" unfolding ccpo.admissible_def by simp (*lemma admissible_False: "\ ccpo.admissible lub ord (\x. False)" unfolding ccpo.admissible_def chain_def by simp *) lemma admissible_const: "ccpo.admissible lub ord (\x. t)" by (auto intro: ccpo.admissibleI) lemma admissible_conj: assumes "ccpo.admissible lub ord (\x. P x)" assumes "ccpo.admissible lub ord (\x. Q x)" shows "ccpo.admissible lub ord (\x. P x \ Q x)" using assms unfolding ccpo.admissible_def by simp lemma admissible_all: assumes "\y. ccpo.admissible lub ord (\x. P x y)" shows "ccpo.admissible lub ord (\x. \y. P x y)" using assms unfolding ccpo.admissible_def by fast lemma admissible_ball: assumes "\y. y \ A \ ccpo.admissible lub ord (\x. P x y)" shows "ccpo.admissible lub ord (\x. \y\A. P x y)" using assms unfolding ccpo.admissible_def by fast lemma chain_compr: "chain ord A \ chain ord {x \ A. P x}" unfolding chain_def by fast context ccpo begin lemma admissible_disj: fixes P Q :: "'a \ bool" assumes P: "ccpo.admissible Sup (\) (\x. P x)" assumes Q: "ccpo.admissible Sup (\) (\x. Q x)" shows "ccpo.admissible Sup (\) (\x. P x \ Q x)" proof (rule ccpo.admissibleI) fix A :: "'a set" assume chain: "chain (\) A" assume A: "A \ {}" and P_Q: "\x\A. P x \ Q x" have "(\x\A. P x) \ (\x\A. \y\A. x \ y \ P y) \ (\x\A. Q x) \ (\x\A. \y\A. x \ y \ Q y)" (is "?P \ ?Q" is "?P1 \ ?P2 \ _") proof (rule disjCI) assume "\ ?Q" then consider "\x\A. \ Q x" | a where "a \ A" "\y\A. a \ y \ \ Q y" by blast then show ?P proof cases case 1 with P_Q have "\x\A. P x" by blast with A show ?P by blast next case 2 note a = \a \ A\ show ?P proof from P_Q 2 have *: "\y\A. a \ y \ P y" by blast with a have "P a" by blast with a show ?P1 by blast show ?P2 proof fix x assume x: "x \ A" with chain a show "\y\A. x \ y \ P y" proof (rule chainE) assume le: "a \ x" with * a x have "P x" by blast with x le show ?thesis by blast next assume "a \ x" with a \P a\ show ?thesis by blast qed qed qed qed qed moreover - have "Sup A = Sup {x \ A. P x}" if "\x\A. \y\A. x \ y \ P y" for P + have "Sup A = Sup {x \ A. P x}" if "\x. x\A \ \y\A. x \ y \ P y" for P proof (rule antisym) have chain_P: "chain (\) {x \ A. P x}" by (rule chain_compr [OF chain]) show "Sup A \ Sup {x \ A. P x}" - apply (rule ccpo_Sup_least [OF chain]) - apply (drule that [rule_format]) - apply clarify - apply (erule order_trans) - apply (simp add: ccpo_Sup_upper [OF chain_P]) - done + proof (rule ccpo_Sup_least [OF chain]) + show "\x. x \ A \ x \ \ {x \ A. P x}" + by (blast intro: ccpo_Sup_upper[OF chain_P] order_trans dest: that) + qed show "Sup {x \ A. P x} \ Sup A" apply (rule ccpo_Sup_least [OF chain_P]) - apply clarify apply (simp add: ccpo_Sup_upper [OF chain]) done qed ultimately consider "\x. x \ A \ P x" "Sup A = Sup {x \ A. P x}" | "\x. x \ A \ Q x" "Sup A = Sup {x \ A. Q x}" by blast then show "P (Sup A) \ Q (Sup A)" - apply cases - apply simp_all - apply (rule disjI1) - apply (rule ccpo.admissibleD [OF P chain_compr [OF chain]]; simp) - apply (rule disjI2) - apply (rule ccpo.admissibleD [OF Q chain_compr [OF chain]]; simp) - done + proof cases + case 1 + then show ?thesis + using ccpo.admissibleD [OF P chain_compr [OF chain]] by force + next + case 2 + then show ?thesis + using ccpo.admissibleD [OF Q chain_compr [OF chain]] by force + qed qed end instance complete_lattice \ ccpo by standard (fast intro: Sup_upper Sup_least)+ lemma lfp_eq_fixp: assumes mono: "mono f" shows "lfp f = fixp f" proof (rule antisym) from mono have f': "monotone (\) (\) f" unfolding mono_def monotone_def . show "lfp f \ fixp f" by (rule lfp_lowerbound, subst fixp_unfold [OF f'], rule order_refl) show "fixp f \ lfp f" by (rule fixp_lowerbound [OF f']) (simp add: lfp_fixpoint [OF mono]) qed hide_const (open) iterates fixp end