(* Title: HOL/Filter.thy Author: Brian Huffman Author: Johannes Hölzl *) section ‹Filters on predicates› theory Filter imports Set_Interval Lifting_Set begin subsection ‹Filters› text ‹ This definition also allows non-proper filters. › locale is_filter = fixes F :: "('a ⇒ bool) ⇒ bool" assumes True: "F (λx. True)" assumes conj: "F (λx. P x) ⟹ F (λx. Q x) ⟹ F (λx. P x ∧ Q x)" assumes mono: "∀x. P x ⟶ Q x ⟹ F (λx. P x) ⟹ F (λx. Q x)" typedef 'a filter = "{F :: ('a ⇒ bool) ⇒ bool. is_filter F}" proof show "(λx. True) ∈ ?filter" by (auto intro: is_filter.intro) qed lemma is_filter_Rep_filter: "is_filter (Rep_filter F)" using Rep_filter [of F] by simp lemma Abs_filter_inverse': assumes "is_filter F" shows "Rep_filter (Abs_filter F) = F" using assms by (simp add: Abs_filter_inverse) subsubsection ‹Eventually› definition eventually :: "('a ⇒ bool) ⇒ 'a filter ⇒ bool" where "eventually P F ⟷ Rep_filter F P" syntax "_eventually" :: "pttrn => 'a filter => bool => bool" ("(3∀⇩_{F}_ in _./ _)" [0, 0, 10] 10) translations "∀⇩_{F}x in F. P" == "CONST eventually (λx. P) F" lemma eventually_Abs_filter: assumes "is_filter F" shows "eventually P (Abs_filter F) = F P" unfolding eventually_def using assms by (simp add: Abs_filter_inverse) lemma filter_eq_iff: shows "F = F' ⟷ (∀P. eventually P F = eventually P F')" unfolding Rep_filter_inject [symmetric] fun_eq_iff eventually_def .. lemma eventually_True [simp]: "eventually (λx. True) F" unfolding eventually_def by (rule is_filter.True [OF is_filter_Rep_filter]) lemma always_eventually: "∀x. P x ⟹ eventually P F" proof - assume "∀x. P x" hence "P = (λx. True)" by (simp add: ext) thus "eventually P F" by simp qed lemma eventuallyI: "(⋀x. P x) ⟹ eventually P F" by (auto intro: always_eventually) lemma eventually_mono: "⟦eventually P F; ⋀x. P x ⟹ Q x⟧ ⟹ eventually Q F" unfolding eventually_def by (blast intro: is_filter.mono [OF is_filter_Rep_filter]) lemma eventually_conj: assumes P: "eventually (λx. P x) F" assumes Q: "eventually (λx. Q x) F" shows "eventually (λx. P x ∧ Q x) F" using assms unfolding eventually_def by (rule is_filter.conj [OF is_filter_Rep_filter]) lemma eventually_mp: assumes "eventually (λx. P x ⟶ Q x) F" assumes "eventually (λx. P x) F" shows "eventually (λx. Q x) F" proof - have "eventually (λx. (P x ⟶ Q x) ∧ P x) F" using assms by (rule eventually_conj) then show ?thesis by (blast intro: eventually_mono) qed lemma eventually_rev_mp: assumes "eventually (λx. P x) F" assumes "eventually (λx. P x ⟶ Q x) F" shows "eventually (λx. Q x) F" using assms(2) assms(1) by (rule eventually_mp) lemma eventually_conj_iff: "eventually (λx. P x ∧ Q x) F ⟷ eventually P F ∧ eventually Q F" by (auto intro: eventually_conj elim: eventually_rev_mp) lemma eventually_elim2: assumes "eventually (λi. P i) F" assumes "eventually (λi. Q i) F" assumes "⋀i. P i ⟹ Q i ⟹ R i" shows "eventually (λi. R i) F" using assms by (auto elim!: eventually_rev_mp) lemma eventually_ball_finite_distrib: "finite A ⟹ (eventually (λx. ∀y∈A. P x y) net) ⟷ (∀y∈A. eventually (λx. P x y) net)" by (induction A rule: finite_induct) (auto simp: eventually_conj_iff) lemma eventually_ball_finite: "finite A ⟹ ∀y∈A. eventually (λx. P x y) net ⟹ eventually (λx. ∀y∈A. P x y) net" by (auto simp: eventually_ball_finite_distrib) lemma eventually_all_finite: fixes P :: "'a ⇒ 'b::finite ⇒ bool" assumes "⋀y. eventually (λx. P x y) net" shows "eventually (λx. ∀y. P x y) net" using eventually_ball_finite [of UNIV P] assms by simp lemma eventually_ex: "(∀⇩_{F}x in F. ∃y. P x y) ⟷ (∃Y. ∀⇩_{F}x in F. P x (Y x))" proof assume "∀⇩_{F}x in F. ∃y. P x y" then have "∀⇩_{F}x in F. P x (SOME y. P x y)" by (auto intro: someI_ex eventually_mono) then show "∃Y. ∀⇩_{F}x in F. P x (Y x)" by auto qed (auto intro: eventually_mono) lemma not_eventually_impI: "eventually P F ⟹ ¬ eventually Q F ⟹ ¬ eventually (λx. P x ⟶ Q x) F" by (auto intro: eventually_mp) lemma not_eventuallyD: "¬ eventually P F ⟹ ∃x. ¬ P x" by (metis always_eventually) lemma eventually_subst: assumes "eventually (λn. P n = Q n) F" shows "eventually P F = eventually Q F" (is "?L = ?R") proof - from assms have "eventually (λx. P x ⟶ Q x) F" and "eventually (λx. Q x ⟶ P x) F" by (auto elim: eventually_mono) then show ?thesis by (auto elim: eventually_elim2) qed subsection ‹ Frequently as dual to eventually › definition frequently :: "('a ⇒ bool) ⇒ 'a filter ⇒ bool" where "frequently P F ⟷ ¬ eventually (λx. ¬ P x) F" syntax "_frequently" :: "pttrn ⇒ 'a filter ⇒ bool ⇒ bool" ("(3∃⇩_{F}_ in _./ _)" [0, 0, 10] 10) translations "∃⇩_{F}x in F. P" == "CONST frequently (λx. P) F" lemma not_frequently_False [simp]: "¬ (∃⇩_{F}x in F. False)" by (simp add: frequently_def) lemma frequently_ex: "∃⇩_{F}x in F. P x ⟹ ∃x. P x" by (auto simp: frequently_def dest: not_eventuallyD) lemma frequentlyE: assumes "frequently P F" obtains x where "P x" using frequently_ex[OF assms] by auto lemma frequently_mp: assumes ev: "∀⇩_{F}x in F. P x ⟶ Q x" and P: "∃⇩_{F}x in F. P x" shows "∃⇩_{F}x in F. Q x" proof - from ev have "eventually (λx. ¬ Q x ⟶ ¬ P x) F" by (rule eventually_rev_mp) (auto intro!: always_eventually) from eventually_mp[OF this] P show ?thesis by (auto simp: frequently_def) qed lemma frequently_rev_mp: assumes "∃⇩_{F}x in F. P x" assumes "∀⇩_{F}x in F. P x ⟶ Q x" shows "∃⇩_{F}x in F. Q x" using assms(2) assms(1) by (rule frequently_mp) lemma frequently_mono: "(∀x. P x ⟶ Q x) ⟹ frequently P F ⟹ frequently Q F" using frequently_mp[of P Q] by (simp add: always_eventually) lemma frequently_elim1: "∃⇩_{F}x in F. P x ⟹ (⋀i. P i ⟹ Q i) ⟹ ∃⇩_{F}x in F. Q x" by (metis frequently_mono) lemma frequently_disj_iff: "(∃⇩_{F}x in F. P x ∨ Q x) ⟷ (∃⇩_{F}x in F. P x) ∨ (∃⇩_{F}x in F. Q x)" by (simp add: frequently_def eventually_conj_iff) lemma frequently_disj: "∃⇩_{F}x in F. P x ⟹ ∃⇩_{F}x in F. Q x ⟹ ∃⇩_{F}x in F. P x ∨ Q x" by (simp add: frequently_disj_iff) lemma frequently_bex_finite_distrib: assumes "finite A" shows "(∃⇩_{F}x in F. ∃y∈A. P x y) ⟷ (∃y∈A. ∃⇩_{F}x in F. P x y)" using assms by induction (auto simp: frequently_disj_iff) lemma frequently_bex_finite: "finite A ⟹ ∃⇩_{F}x in F. ∃y∈A. P x y ⟹ ∃y∈A. ∃⇩_{F}x in F. P x y" by (simp add: frequently_bex_finite_distrib) lemma frequently_all: "(∃⇩_{F}x in F. ∀y. P x y) ⟷ (∀Y. ∃⇩_{F}x in F. P x (Y x))" using eventually_ex[of "λx y. ¬ P x y" F] by (simp add: frequently_def) lemma shows not_eventually: "¬ eventually P F ⟷ (∃⇩_{F}x in F. ¬ P x)" and not_frequently: "¬ frequently P F ⟷ (∀⇩_{F}x in F. ¬ P x)" by (auto simp: frequently_def) lemma frequently_imp_iff: "(∃⇩_{F}x in F. P x ⟶ Q x) ⟷ (eventually P F ⟶ frequently Q F)" unfolding imp_conv_disj frequently_disj_iff not_eventually[symmetric] .. lemma eventually_frequently_const_simps: "(∃⇩_{F}x in F. P x ∧ C) ⟷ (∃⇩_{F}x in F. P x) ∧ C" "(∃⇩_{F}x in F. C ∧ P x) ⟷ C ∧ (∃⇩_{F}x in F. P x)" "(∀⇩_{F}x in F. P x ∨ C) ⟷ (∀⇩_{F}x in F. P x) ∨ C" "(∀⇩_{F}x in F. C ∨ P x) ⟷ C ∨ (∀⇩_{F}x in F. P x)" "(∀⇩_{F}x in F. P x ⟶ C) ⟷ ((∃⇩_{F}x in F. P x) ⟶ C)" "(∀⇩_{F}x in F. C ⟶ P x) ⟷ (C ⟶ (∀⇩_{F}x in F. P x))" by (cases C; simp add: not_frequently)+ lemmas eventually_frequently_simps = eventually_frequently_const_simps not_eventually eventually_conj_iff eventually_ball_finite_distrib eventually_ex not_frequently frequently_disj_iff frequently_bex_finite_distrib frequently_all frequently_imp_iff ML ‹ fun eventually_elim_tac facts = CONTEXT_SUBGOAL (fn (goal, i) => fn (ctxt, st) => let val mp_thms = facts RL @{thms eventually_rev_mp} val raw_elim_thm = (@{thm allI} RS @{thm always_eventually}) |> fold (fn thm1 => fn thm2 => thm2 RS thm1) mp_thms |> fold (fn _ => fn thm => @{thm impI} RS thm) facts val cases_prop = Thm.prop_of (Rule_Cases.internalize_params (raw_elim_thm RS Goal.init (Thm.cterm_of ctxt goal))) val cases = Rule_Cases.make_common ctxt cases_prop [(("elim", []), [])] in CONTEXT_CASES cases (resolve_tac ctxt [raw_elim_thm] i) (ctxt, st) end) › method_setup eventually_elim = ‹ Scan.succeed (fn _ => CONTEXT_METHOD (fn facts => eventually_elim_tac facts 1)) › "elimination of eventually quantifiers" subsubsection ‹Finer-than relation› text ‹@{term "F ≤ F'"} means that filter @{term F} is finer than filter @{term F'}.› instantiation filter :: (type) complete_lattice begin definition le_filter_def: "F ≤ F' ⟷ (∀P. eventually P F' ⟶ eventually P F)" definition "(F :: 'a filter) < F' ⟷ F ≤ F' ∧ ¬ F' ≤ F" definition "top = Abs_filter (λP. ∀x. P x)" definition "bot = Abs_filter (λP. True)" definition "sup F F' = Abs_filter (λP. eventually P F ∧ eventually P F')" definition "inf F F' = Abs_filter (λP. ∃Q R. eventually Q F ∧ eventually R F' ∧ (∀x. Q x ∧ R x ⟶ P x))" definition "Sup S = Abs_filter (λP. ∀F∈S. eventually P F)" definition "Inf S = Sup {F::'a filter. ∀F'∈S. F ≤ F'}" lemma eventually_top [simp]: "eventually P top ⟷ (∀x. P x)" unfolding top_filter_def by (rule eventually_Abs_filter, rule is_filter.intro, auto) lemma eventually_bot [simp]: "eventually P bot" unfolding bot_filter_def by (subst eventually_Abs_filter, rule is_filter.intro, auto) lemma eventually_sup: "eventually P (sup F F') ⟷ eventually P F ∧ eventually P F'" unfolding sup_filter_def by (rule eventually_Abs_filter, rule is_filter.intro) (auto elim!: eventually_rev_mp) lemma eventually_inf: "eventually P (inf F F') ⟷ (∃Q R. eventually Q F ∧ eventually R F' ∧ (∀x. Q x ∧ R x ⟶ P x))" unfolding inf_filter_def apply (rule eventually_Abs_filter, rule is_filter.intro) apply (fast intro: eventually_True) apply clarify apply (intro exI conjI) apply (erule (1) eventually_conj) apply (erule (1) eventually_conj) apply simp apply auto done lemma eventually_Sup: "eventually P (Sup S) ⟷ (∀F∈S. eventually P F)" unfolding Sup_filter_def apply (rule eventually_Abs_filter, rule is_filter.intro) apply (auto intro: eventually_conj elim!: eventually_rev_mp) done instance proof fix F F' F'' :: "'a filter" and S :: "'a filter set" { show "F < F' ⟷ F ≤ F' ∧ ¬ F' ≤ F" by (rule less_filter_def) } { show "F ≤ F" unfolding le_filter_def by simp } { assume "F ≤ F'" and "F' ≤ F''" thus "F ≤ F''" unfolding le_filter_def by simp } { assume "F ≤ F'" and "F' ≤ F" thus "F = F'" unfolding le_filter_def filter_eq_iff by fast } { show "inf F F' ≤ F" and "inf F F' ≤ F'" unfolding le_filter_def eventually_inf by (auto intro: eventually_True) } { assume "F ≤ F'" and "F ≤ F''" thus "F ≤ inf F' F''" unfolding le_filter_def eventually_inf by (auto intro: eventually_mono [OF eventually_conj]) } { show "F ≤ sup F F'" and "F' ≤ sup F F'" unfolding le_filter_def eventually_sup by simp_all } { assume "F ≤ F''" and "F' ≤ F''" thus "sup F F' ≤ F''" unfolding le_filter_def eventually_sup by simp } { assume "F'' ∈ S" thus "Inf S ≤ F''" unfolding le_filter_def Inf_filter_def eventually_Sup Ball_def by simp } { assume "⋀F'. F' ∈ S ⟹ F ≤ F'" thus "F ≤ Inf S" unfolding le_filter_def Inf_filter_def eventually_Sup Ball_def by simp } { assume "F ∈ S" thus "F ≤ Sup S" unfolding le_filter_def eventually_Sup by simp } { assume "⋀F. F ∈ S ⟹ F ≤ F'" thus "Sup S ≤ F'" unfolding le_filter_def eventually_Sup by simp } { show "Inf {} = (top::'a filter)" by (auto simp: top_filter_def Inf_filter_def Sup_filter_def) (metis (full_types) top_filter_def always_eventually eventually_top) } { show "Sup {} = (bot::'a filter)" by (auto simp: bot_filter_def Sup_filter_def) } qed end instance filter :: (type) distrib_lattice proof fix F G H :: "'a filter" show "sup F (inf G H) = inf (sup F G) (sup F H)" proof (rule order.antisym) show "inf (sup F G) (sup F H) ≤ sup F (inf G H)" unfolding le_filter_def eventually_sup proof safe fix P assume 1: "eventually P F" and 2: "eventually P (inf G H)" from 2 obtain Q R where QR: "eventually Q G" "eventually R H" "⋀x. Q x ⟹ R x ⟹ P x" by (auto simp: eventually_inf) define Q' where "Q' = (λx. Q x ∨ P x)" define R' where "R' = (λx. R x ∨ P x)" from 1 have "eventually Q' F" by (elim eventually_mono) (auto simp: Q'_def) moreover from 1 have "eventually R' F" by (elim eventually_mono) (auto simp: R'_def) moreover from QR(1) have "eventually Q' G" by (elim eventually_mono) (auto simp: Q'_def) moreover from QR(2) have "eventually R' H" by (elim eventually_mono)(auto simp: R'_def) moreover from QR have "P x" if "Q' x" "R' x" for x using that by (auto simp: Q'_def R'_def) ultimately show "eventually P (inf (sup F G) (sup F H))" by (auto simp: eventually_inf eventually_sup) qed qed (auto intro: inf.coboundedI1 inf.coboundedI2) qed lemma filter_leD: "F ≤ F' ⟹ eventually P F' ⟹ eventually P F" unfolding le_filter_def by simp lemma filter_leI: "(⋀P. eventually P F' ⟹ eventually P F) ⟹ F ≤ F'" unfolding le_filter_def by simp lemma eventually_False: "eventually (λx. False) F ⟷ F = bot" unfolding filter_eq_iff by (auto elim: eventually_rev_mp) lemma eventually_frequently: "F ≠ bot ⟹ eventually P F ⟹ frequently P F" using eventually_conj[of P F "λx. ¬ P x"] by (auto simp add: frequently_def eventually_False) lemma eventually_const_iff: "eventually (λx. P) F ⟷ P ∨ F = bot" by (cases P) (auto simp: eventually_False) lemma eventually_const[simp]: "F ≠ bot ⟹ eventually (λx. P) F ⟷ P" by (simp add: eventually_const_iff) lemma frequently_const_iff: "frequently (λx. P) F ⟷ P ∧ F ≠ bot" by (simp add: frequently_def eventually_const_iff) lemma frequently_const[simp]: "F ≠ bot ⟹ frequently (λx. P) F ⟷ P" by (simp add: frequently_const_iff) lemma eventually_happens: "eventually P net ⟹ net = bot ∨ (∃x. P x)" by (metis frequentlyE eventually_frequently) lemma eventually_happens': assumes "F ≠ bot" "eventually P F" shows "∃x. P x" using assms eventually_frequently frequentlyE by blast abbreviation (input) trivial_limit :: "'a filter ⇒ bool" where "trivial_limit F ≡ F = bot" lemma trivial_limit_def: "trivial_limit F ⟷ eventually (λx. False) F" by (rule eventually_False [symmetric]) lemma False_imp_not_eventually: "(∀x. ¬ P x ) ⟹ ¬ trivial_limit net ⟹ ¬ eventually (λx. P x) net" by (simp add: eventually_False) lemma eventually_Inf: "eventually P (Inf B) ⟷ (∃X⊆B. finite X ∧ eventually P (Inf X))" proof - let ?F = "λP. ∃X⊆B. finite X ∧ eventually P (Inf X)" { fix P have "eventually P (Abs_filter ?F) ⟷ ?F P" proof (rule eventually_Abs_filter is_filter.intro)+ show "?F (λx. True)" by (rule exI[of _ "{}"]) (simp add: le_fun_def) next fix P Q assume "?F P" then guess X .. moreover assume "?F Q" then guess Y .. ultimately show "?F (λx. P x ∧ Q x)" by (intro exI[of _ "X ∪ Y"]) (auto simp: Inf_union_distrib eventually_inf) next fix P Q assume "?F P" then guess X .. moreover assume "∀x. P x ⟶ Q x" ultimately show "?F Q" by (intro exI[of _ X]) (auto elim: eventually_mono) qed } note eventually_F = this have "Inf B = Abs_filter ?F" proof (intro antisym Inf_greatest) show "Inf B ≤ Abs_filter ?F" by (auto simp: le_filter_def eventually_F dest: Inf_superset_mono) next fix F assume "F ∈ B" then show "Abs_filter ?F ≤ F" by (auto simp add: le_filter_def eventually_F intro!: exI[of _ "{F}"]) qed then show ?thesis by (simp add: eventually_F) qed lemma eventually_INF: "eventually P (INF b:B. F b) ⟷ (∃X⊆B. finite X ∧ eventually P (INF b:X. F b))" unfolding eventually_Inf [of P "F`B"] by (metis finite_imageI image_mono finite_subset_image) lemma Inf_filter_not_bot: fixes B :: "'a filter set" shows "(⋀X. X ⊆ B ⟹ finite X ⟹ Inf X ≠ bot) ⟹ Inf B ≠ bot" unfolding trivial_limit_def eventually_Inf[of _ B] bot_bool_def [symmetric] bot_fun_def [symmetric] bot_unique by simp lemma INF_filter_not_bot: fixes F :: "'i ⇒ 'a filter" shows "(⋀X. X ⊆ B ⟹ finite X ⟹ (INF b:X. F b) ≠ bot) ⟹ (INF b:B. F b) ≠ bot" unfolding trivial_limit_def eventually_INF [of _ _ B] bot_bool_def [symmetric] bot_fun_def [symmetric] bot_unique by simp lemma eventually_Inf_base: assumes "B ≠ {}" and base: "⋀F G. F ∈ B ⟹ G ∈ B ⟹ ∃x∈B. x ≤ inf F G" shows "eventually P (Inf B) ⟷ (∃b∈B. eventually P b)" proof (subst eventually_Inf, safe) fix X assume "finite X" "X ⊆ B" then have "∃b∈B. ∀x∈X. b ≤ x" proof induct case empty then show ?case using ‹B ≠ {}› by auto next case (insert x X) then obtain b where "b ∈ B" "⋀x. x ∈ X ⟹ b ≤ x" by auto with ‹insert x X ⊆ B› base[of b x] show ?case by (auto intro: order_trans) qed then obtain b where "b ∈ B" "b ≤ Inf X" by (auto simp: le_Inf_iff) then show "eventually P (Inf X) ⟹ Bex B (eventually P)" by (intro bexI[of _ b]) (auto simp: le_filter_def) qed (auto intro!: exI[of _ "{x}" for x]) lemma eventually_INF_base: "B ≠ {} ⟹ (⋀a b. a ∈ B ⟹ b ∈ B ⟹ ∃x∈B. F x ≤ inf (F a) (F b)) ⟹ eventually P (INF b:B. F b) ⟷ (∃b∈B. eventually P (F b))" by (subst eventually_Inf_base) auto lemma eventually_INF1: "i ∈ I ⟹ eventually P (F i) ⟹ eventually P (INF i:I. F i)" using filter_leD[OF INF_lower] . lemma eventually_INF_mono: assumes *: "∀⇩_{F}x in ⨅i∈I. F i. P x" assumes T1: "⋀Q R P. (⋀x. Q x ∧ R x ⟶ P x) ⟹ (⋀x. T Q x ⟹ T R x ⟹ T P x)" assumes T2: "⋀P. (⋀x. P x) ⟹ (⋀x. T P x)" assumes **: "⋀i P. i ∈ I ⟹ ∀⇩_{F}x in F i. P x ⟹ ∀⇩_{F}x in F' i. T P x" shows "∀⇩_{F}x in ⨅i∈I. F' i. T P x" proof - from * obtain X where X: "finite X" "X ⊆ I" "∀⇩_{F}x in ⨅i∈X. F i. P x" unfolding eventually_INF[of _ _ I] by auto then have "eventually (T P) (INFIMUM X F')" apply (induction X arbitrary: P) apply (auto simp: eventually_inf T2) subgoal for x S P Q R apply (intro exI[of _ "T Q"]) apply (auto intro!: **) [] apply (intro exI[of _ "T R"]) apply (auto intro: T1) [] done done with X show "∀⇩_{F}x in ⨅i∈I. F' i. T P x" by (subst eventually_INF) auto qed subsubsection ‹Map function for filters› definition filtermap :: "('a ⇒ 'b) ⇒ 'a filter ⇒ 'b filter" where "filtermap f F = Abs_filter (λP. eventually (λx. P (f x)) F)" lemma eventually_filtermap: "eventually P (filtermap f F) = eventually (λx. P (f x)) F" unfolding filtermap_def apply (rule eventually_Abs_filter) apply (rule is_filter.intro) apply (auto elim!: eventually_rev_mp) done lemma filtermap_ident: "filtermap (λx. x) F = F" by (simp add: filter_eq_iff eventually_filtermap) lemma filtermap_filtermap: "filtermap f (filtermap g F) = filtermap (λx. f (g x)) F" by (simp add: filter_eq_iff eventually_filtermap) lemma filtermap_mono: "F ≤ F' ⟹ filtermap f F ≤ filtermap f F'" unfolding le_filter_def eventually_filtermap by simp lemma filtermap_bot [simp]: "filtermap f bot = bot" by (simp add: filter_eq_iff eventually_filtermap) lemma filtermap_sup: "filtermap f (sup F1 F2) = sup (filtermap f F1) (filtermap f F2)" by (auto simp: filter_eq_iff eventually_filtermap eventually_sup) lemma filtermap_inf: "filtermap f (inf F1 F2) ≤ inf (filtermap f F1) (filtermap f F2)" by (auto simp: le_filter_def eventually_filtermap eventually_inf) lemma filtermap_INF: "filtermap f (INF b:B. F b) ≤ (INF b:B. filtermap f (F b))" proof - { fix X :: "'c set" assume "finite X" then have "filtermap f (INFIMUM X F) ≤ (INF b:X. filtermap f (F b))" proof induct case (insert x X) have "filtermap f (INF a:insert x X. F a) ≤ inf (filtermap f (F x)) (filtermap f (INF a:X. F a))" by (rule order_trans[OF _ filtermap_inf]) simp also have "… ≤ inf (filtermap f (F x)) (INF a:X. filtermap f (F a))" by (intro inf_mono insert order_refl) finally show ?case by simp qed simp } then show ?thesis unfolding le_filter_def eventually_filtermap by (subst (1 2) eventually_INF) auto qed subsubsection ‹Contravariant map function for filters› definition filtercomap :: "('a ⇒ 'b) ⇒ 'b filter ⇒ 'a filter" where "filtercomap f F = Abs_filter (λP. ∃Q. eventually Q F ∧ (∀x. Q (f x) ⟶ P x))" lemma eventually_filtercomap: "eventually P (filtercomap f F) ⟷ (∃Q. eventually Q F ∧ (∀x. Q (f x) ⟶ P x))" unfolding filtercomap_def proof (intro eventually_Abs_filter, unfold_locales, goal_cases) case 1 show ?case by (auto intro!: exI[of _ "λ_. True"]) next case (2 P Q) from 2(1) guess P' by (elim exE conjE) note P' = this from 2(2) guess Q' by (elim exE conjE) note Q' = this show ?case by (rule exI[of _ "λx. P' x ∧ Q' x"]) (insert P' Q', auto intro!: eventually_conj) next case (3 P Q) thus ?case by blast qed lemma filtercomap_ident: "filtercomap (λx. x) F = F" by (auto simp: filter_eq_iff eventually_filtercomap elim!: eventually_mono) lemma filtercomap_filtercomap: "filtercomap f (filtercomap g F) = filtercomap (λx. g (f x)) F" unfolding filter_eq_iff by (auto simp: eventually_filtercomap) lemma filtercomap_mono: "F ≤ F' ⟹ filtercomap f F ≤ filtercomap f F'" by (auto simp: eventually_filtercomap le_filter_def) lemma filtercomap_bot [simp]: "filtercomap f bot = bot" by (auto simp: filter_eq_iff eventually_filtercomap) lemma filtercomap_top [simp]: "filtercomap f top = top" by (auto simp: filter_eq_iff eventually_filtercomap) lemma filtercomap_inf: "filtercomap f (inf F1 F2) = inf (filtercomap f F1) (filtercomap f F2)" unfolding filter_eq_iff proof safe fix P assume "eventually P (filtercomap f (F1 ⊓ F2))" then obtain Q R S where *: "eventually Q F1" "eventually R F2" "⋀x. Q x ⟹ R x ⟹ S x" "⋀x. S (f x) ⟹ P x" unfolding eventually_filtercomap eventually_inf by blast from * have "eventually (λx. Q (f x)) (filtercomap f F1)" "eventually (λx. R (f x)) (filtercomap f F2)" by (auto simp: eventually_filtercomap) with * show "eventually P (filtercomap f F1 ⊓ filtercomap f F2)" unfolding eventually_inf by blast next fix P assume "eventually P (inf (filtercomap f F1) (filtercomap f F2))" then obtain Q Q' R R' where *: "eventually Q F1" "eventually R F2" "⋀x. Q (f x) ⟹ Q' x" "⋀x. R (f x) ⟹ R' x" "⋀x. Q' x ⟹ R' x ⟹ P x" unfolding eventually_filtercomap eventually_inf by blast from * have "eventually (λx. Q x ∧ R x) (F1 ⊓ F2)" by (auto simp: eventually_inf) with * show "eventually P (filtercomap f (F1 ⊓ F2))" by (auto simp: eventually_filtercomap) qed lemma filtercomap_sup: "filtercomap f (sup F1 F2) ≥ sup (filtercomap f F1) (filtercomap f F2)" unfolding le_filter_def proof safe fix P assume "eventually P (filtercomap f (sup F1 F2))" thus "eventually P (sup (filtercomap f F1) (filtercomap f F2))" by (auto simp: filter_eq_iff eventually_filtercomap eventually_sup) qed lemma filtercomap_INF: "filtercomap f (INF b:B. F b) = (INF b:B. filtercomap f (F b))" proof - have *: "filtercomap f (INF b:B. F b) = (INF b:B. filtercomap f (F b))" if "finite B" for B using that by induction (simp_all add: filtercomap_inf) show ?thesis unfolding filter_eq_iff proof fix P have "eventually P (INF b:B. filtercomap f (F b)) ⟷ (∃X. (X ⊆ B ∧ finite X) ∧ eventually P (⨅b∈X. filtercomap f (F b)))" by (subst eventually_INF) blast also have "… ⟷ (∃X. (X ⊆ B ∧ finite X) ∧ eventually P (filtercomap f (INF b:X. F b)))" by (rule ex_cong) (simp add: *) also have "… ⟷ eventually P (filtercomap f (INFIMUM B F))" unfolding eventually_filtercomap by (subst eventually_INF) blast finally show "eventually P (filtercomap f (INFIMUM B F)) = eventually P (⨅b∈B. filtercomap f (F b))" .. qed qed lemma filtercomap_SUP_finite: "finite B ⟹ filtercomap f (SUP b:B. F b) ≥ (SUP b:B. filtercomap f (F b))" by (induction B rule: finite_induct) (auto intro: order_trans[OF _ order_trans[OF _ filtercomap_sup]] filtercomap_mono) lemma eventually_filtercomapI [intro]: assumes "eventually P F" shows "eventually (λx. P (f x)) (filtercomap f F)" using assms by (auto simp: eventually_filtercomap) lemma filtermap_filtercomap: "filtermap f (filtercomap f F) ≤ F" by (auto simp: le_filter_def eventually_filtermap eventually_filtercomap) lemma filtercomap_filtermap: "filtercomap f (filtermap f F) ≥ F" unfolding le_filter_def eventually_filtermap eventually_filtercomap by (auto elim!: eventually_mono) subsubsection ‹Standard filters› definition principal :: "'a set ⇒ 'a filter" where "principal S = Abs_filter (λP. ∀x∈S. P x)" lemma eventually_principal: "eventually P (principal S) ⟷ (∀x∈S. P x)" unfolding principal_def by (rule eventually_Abs_filter, rule is_filter.intro) auto lemma eventually_inf_principal: "eventually P (inf F (principal s)) ⟷ eventually (λx. x ∈ s ⟶ P x) F" unfolding eventually_inf eventually_principal by (auto elim: eventually_mono) lemma principal_UNIV[simp]: "principal UNIV = top" by (auto simp: filter_eq_iff eventually_principal) lemma principal_empty[simp]: "principal {} = bot" by (auto simp: filter_eq_iff eventually_principal) lemma principal_eq_bot_iff: "principal X = bot ⟷ X = {}" by (auto simp add: filter_eq_iff eventually_principal) lemma principal_le_iff[iff]: "principal A ≤ principal B ⟷ A ⊆ B" by (auto simp: le_filter_def eventually_principal) lemma le_principal: "F ≤ principal A ⟷ eventually (λx. x ∈ A) F" unfolding le_filter_def eventually_principal apply safe apply (erule_tac x="λx. x ∈ A" in allE) apply (auto elim: eventually_mono) done lemma principal_inject[iff]: "principal A = principal B ⟷ A = B" unfolding eq_iff by simp lemma sup_principal[simp]: "sup (principal A) (principal B) = principal (A ∪ B)" unfolding filter_eq_iff eventually_sup eventually_principal by auto lemma inf_principal[simp]: "inf (principal A) (principal B) = principal (A ∩ B)" unfolding filter_eq_iff eventually_inf eventually_principal by (auto intro: exI[of _ "λx. x ∈ A"] exI[of _ "λx. x ∈ B"]) lemma SUP_principal[simp]: "(SUP i : I. principal (A i)) = principal (⋃i∈I. A i)" unfolding filter_eq_iff eventually_Sup by (auto simp: eventually_principal) lemma INF_principal_finite: "finite X ⟹ (INF x:X. principal (f x)) = principal (⋂x∈X. f x)" by (induct X rule: finite_induct) auto lemma filtermap_principal[simp]: "filtermap f (principal A) = principal (f ` A)" unfolding filter_eq_iff eventually_filtermap eventually_principal by simp lemma filtercomap_principal[simp]: "filtercomap f (principal A) = principal (f -` A)" unfolding filter_eq_iff eventually_filtercomap eventually_principal by fast subsubsection ‹Order filters› definition at_top :: "('a::order) filter" where "at_top = (INF k. principal {k ..})" lemma at_top_sub: "at_top = (INF k:{c::'a::linorder..}. principal {k ..})" by (auto intro!: INF_eq max.cobounded1 max.cobounded2 simp: at_top_def) lemma eventually_at_top_linorder: "eventually P at_top ⟷ (∃N::'a::linorder. ∀n≥N. P n)" unfolding at_top_def by (subst eventually_INF_base) (auto simp: eventually_principal intro: max.cobounded1 max.cobounded2) lemma eventually_filtercomap_at_top_linorder: "eventually P (filtercomap f at_top) ⟷ (∃N::'a::linorder. ∀x. f x ≥ N ⟶ P x)" by (auto simp: eventually_filtercomap eventually_at_top_linorder) lemma eventually_at_top_linorderI: fixes c::"'a::linorder" assumes "⋀x. c ≤ x ⟹ P x" shows "eventually P at_top" using assms by (auto simp: eventually_at_top_linorder) lemma eventually_ge_at_top [simp]: "eventually (λx. (c::_::linorder) ≤ x) at_top" unfolding eventually_at_top_linorder by auto lemma eventually_at_top_dense: "eventually P at_top ⟷ (∃N::'a::{no_top, linorder}. ∀n>N. P n)" proof - have "eventually P (INF k. principal {k <..}) ⟷ (∃N::'a. ∀n>N. P n)" by (subst eventually_INF_base) (auto simp: eventually_principal intro: max.cobounded1 max.cobounded2) also have "(INF k. principal {k::'a <..}) = at_top" unfolding at_top_def by (intro INF_eq) (auto intro: less_imp_le simp: Ici_subset_Ioi_iff gt_ex) finally show ?thesis . qed lemma eventually_filtercomap_at_top_dense: "eventually P (filtercomap f at_top) ⟷ (∃N::'a::{no_top, linorder}. ∀x. f x > N ⟶ P x)" by (auto simp: eventually_filtercomap eventually_at_top_dense) lemma eventually_at_top_not_equal [simp]: "eventually (λx::'a::{no_top, linorder}. x ≠ c) at_top" unfolding eventually_at_top_dense by auto lemma eventually_gt_at_top [simp]: "eventually (λx. (c::_::{no_top, linorder}) < x) at_top" unfolding eventually_at_top_dense by auto lemma eventually_all_ge_at_top: assumes "eventually P (at_top :: ('a :: linorder) filter)" shows "eventually (λx. ∀y≥x. P y) at_top" proof - from assms obtain x where "⋀y. y ≥ x ⟹ P y" by (auto simp: eventually_at_top_linorder) hence "∀z≥y. P z" if "y ≥ x" for y using that by simp thus ?thesis by (auto simp: eventually_at_top_linorder) qed definition at_bot :: "('a::order) filter" where "at_bot = (INF k. principal {.. k})" lemma at_bot_sub: "at_bot = (INF k:{.. c::'a::linorder}. principal {.. k})" by (auto intro!: INF_eq min.cobounded1 min.cobounded2 simp: at_bot_def) lemma eventually_at_bot_linorder: fixes P :: "'a::linorder ⇒ bool" shows "eventually P at_bot ⟷ (∃N. ∀n≤N. P n)" unfolding at_bot_def by (subst eventually_INF_base) (auto simp: eventually_principal intro: min.cobounded1 min.cobounded2) lemma eventually_filtercomap_at_bot_linorder: "eventually P (filtercomap f at_bot) ⟷ (∃N::'a::linorder. ∀x. f x ≤ N ⟶ P x)" by (auto simp: eventually_filtercomap eventually_at_bot_linorder) lemma eventually_le_at_bot [simp]: "eventually (λx. x ≤ (c::_::linorder)) at_bot" unfolding eventually_at_bot_linorder by auto lemma eventually_at_bot_dense: "eventually P at_bot ⟷ (∃N::'a::{no_bot, linorder}. ∀n<N. P n)" proof - have "eventually P (INF k. principal {..< k}) ⟷ (∃N::'a. ∀n<N. P n)" by (subst eventually_INF_base) (auto simp: eventually_principal intro: min.cobounded1 min.cobounded2) also have "(INF k. principal {..< k::'a}) = at_bot" unfolding at_bot_def by (intro INF_eq) (auto intro: less_imp_le simp: Iic_subset_Iio_iff lt_ex) finally show ?thesis . qed lemma eventually_filtercomap_at_bot_dense: "eventually P (filtercomap f at_bot) ⟷ (∃N::'a::{no_bot, linorder}. ∀x. f x < N ⟶ P x)" by (auto simp: eventually_filtercomap eventually_at_bot_dense) lemma eventually_at_bot_not_equal [simp]: "eventually (λx::'a::{no_bot, linorder}. x ≠ c) at_bot" unfolding eventually_at_bot_dense by auto lemma eventually_gt_at_bot [simp]: "eventually (λx. x < (c::_::unbounded_dense_linorder)) at_bot" unfolding eventually_at_bot_dense by auto lemma trivial_limit_at_bot_linorder [simp]: "¬ trivial_limit (at_bot ::('a::linorder) filter)" unfolding trivial_limit_def by (metis eventually_at_bot_linorder order_refl) lemma trivial_limit_at_top_linorder [simp]: "¬ trivial_limit (at_top ::('a::linorder) filter)" unfolding trivial_limit_def by (metis eventually_at_top_linorder order_refl) subsection ‹Sequentially› abbreviation sequentially :: "nat filter" where "sequentially ≡ at_top" lemma eventually_sequentially: "eventually P sequentially ⟷ (∃N. ∀n≥N. P n)" by (rule eventually_at_top_linorder) lemma sequentially_bot [simp, intro]: "sequentially ≠ bot" unfolding filter_eq_iff eventually_sequentially by auto lemmas trivial_limit_sequentially = sequentially_bot lemma eventually_False_sequentially [simp]: "¬ eventually (λn. False) sequentially" by (simp add: eventually_False) lemma le_sequentially: "F ≤ sequentially ⟷ (∀N. eventually (λn. N ≤ n) F)" by (simp add: at_top_def le_INF_iff le_principal) lemma eventually_sequentiallyI [intro?]: assumes "⋀x. c ≤ x ⟹ P x" shows "eventually P sequentially" using assms by (auto simp: eventually_sequentially) lemma eventually_sequentially_Suc [simp]: "eventually (λi. P (Suc i)) sequentially ⟷ eventually P sequentially" unfolding eventually_sequentially by (metis Suc_le_D Suc_le_mono le_Suc_eq) lemma eventually_sequentially_seg [simp]: "eventually (λn. P (n + k)) sequentially ⟷ eventually P sequentially" using eventually_sequentially_Suc[of "λn. P (n + k)" for k] by (induction k) auto subsection ‹The cofinite filter› definition "cofinite = Abs_filter (λP. finite {x. ¬ P x})" abbreviation Inf_many :: "('a ⇒ bool) ⇒ bool" (binder "∃⇩_{∞}" 10) where "Inf_many P ≡ frequently P cofinite" abbreviation Alm_all :: "('a ⇒ bool) ⇒ bool" (binder "∀⇩_{∞}" 10) where "Alm_all P ≡ eventually P cofinite" notation (ASCII) Inf_many (binder "INFM " 10) and Alm_all (binder "MOST " 10) lemma eventually_cofinite: "eventually P cofinite ⟷ finite {x. ¬ P x}" unfolding cofinite_def proof (rule eventually_Abs_filter, rule is_filter.intro) fix P Q :: "'a ⇒ bool" assume "finite {x. ¬ P x}" "finite {x. ¬ Q x}" from finite_UnI[OF this] show "finite {x. ¬ (P x ∧ Q x)}" by (rule rev_finite_subset) auto next fix P Q :: "'a ⇒ bool" assume P: "finite {x. ¬ P x}" and *: "∀x. P x ⟶ Q x" from * show "finite {x. ¬ Q x}" by (intro finite_subset[OF _ P]) auto qed simp lemma frequently_cofinite: "frequently P cofinite ⟷ ¬ finite {x. P x}" by (simp add: frequently_def eventually_cofinite) lemma cofinite_bot[simp]: "cofinite = (bot::'a filter) ⟷ finite (UNIV :: 'a set)" unfolding trivial_limit_def eventually_cofinite by simp lemma cofinite_eq_sequentially: "cofinite = sequentially" unfolding filter_eq_iff eventually_sequentially eventually_cofinite proof safe fix P :: "nat ⇒ bool" assume [simp]: "finite {x. ¬ P x}" show "∃N. ∀n≥N. P n" proof cases assume "{x. ¬ P x} ≠ {}" then show ?thesis by (intro exI[of _ "Suc (Max {x. ¬ P x})"]) (auto simp: Suc_le_eq) qed auto next fix P :: "nat ⇒ bool" and N :: nat assume "∀n≥N. P n" then have "{x. ¬ P x} ⊆ {..< N}" by (auto simp: not_le) then show "finite {x. ¬ P x}" by (blast intro: finite_subset) qed subsubsection ‹Product of filters› lemma filtermap_sequentually_ne_bot: "filtermap f sequentially ≠ bot" by (auto simp add: filter_eq_iff eventually_filtermap eventually_sequentially) definition prod_filter :: "'a filter ⇒ 'b filter ⇒ ('a × 'b) filter" (infixr "×⇩_{F}" 80) where "prod_filter F G = (INF (P, Q):{(P, Q). eventually P F ∧ eventually Q G}. principal {(x, y). P x ∧ Q y})" lemma eventually_prod_filter: "eventually P (F ×⇩_{F}G) ⟷ (∃Pf Pg. eventually Pf F ∧ eventually Pg G ∧ (∀x y. Pf x ⟶ Pg y ⟶ P (x, y)))" unfolding prod_filter_def proof (subst eventually_INF_base, goal_cases) case 2 moreover have "eventually Pf F ⟹ eventually Qf F ⟹ eventually Pg G ⟹ eventually Qg G ⟹ ∃P Q. eventually P F ∧ eventually Q G ∧ Collect P × Collect Q ⊆ Collect Pf × Collect Pg ∩ Collect Qf × Collect Qg" for Pf Pg Qf Qg by (intro conjI exI[of _ "inf Pf Qf"] exI[of _ "inf Pg Qg"]) (auto simp: inf_fun_def eventually_conj) ultimately show ?case by auto qed (auto simp: eventually_principal intro: eventually_True) lemma eventually_prod1: assumes "B ≠ bot" shows "(∀⇩_{F}(x, y) in A ×⇩_{F}B. P x) ⟷ (∀⇩_{F}x in A. P x)" unfolding eventually_prod_filter proof safe fix R Q assume *: "∀⇩_{F}x in A. R x" "∀⇩_{F}x in B. Q x" "∀x y. R x ⟶ Q y ⟶ P x" with ‹B ≠ bot› obtain y where "Q y" by (auto dest: eventually_happens) with * show "eventually P A" by (force elim: eventually_mono) next assume "eventually P A" then show "∃Pf Pg. eventually Pf A ∧ eventually Pg B ∧ (∀x y. Pf x ⟶ Pg y ⟶ P x)" by (intro exI[of _ P] exI[of _ "λx. True"]) auto qed lemma eventually_prod2: assumes "A ≠ bot" shows "(∀⇩_{F}(x, y) in A ×⇩_{F}B. P y) ⟷ (∀⇩_{F}y in B. P y)" unfolding eventually_prod_filter proof safe fix R Q assume *: "∀⇩_{F}x in A. R x" "∀⇩_{F}x in B. Q x" "∀x y. R x ⟶ Q y ⟶ P y" with ‹A ≠ bot› obtain x where "R x" by (auto dest: eventually_happens) with * show "eventually P B" by (force elim: eventually_mono) next assume "eventually P B" then show "∃Pf Pg. eventually Pf A ∧ eventually Pg B ∧ (∀x y. Pf x ⟶ Pg y ⟶ P y)" by (intro exI[of _ P] exI[of _ "λx. True"]) auto qed lemma INF_filter_bot_base: fixes F :: "'a ⇒ 'b filter" assumes *: "⋀i j. i ∈ I ⟹ j ∈ I ⟹ ∃k∈I. F k ≤ F i ⊓ F j" shows "(INF i:I. F i) = bot ⟷ (∃i∈I. F i = bot)" proof (cases "∃i∈I. F i = bot") case True then have "(INF i:I. F i) ≤ bot" by (auto intro: INF_lower2) with True show ?thesis by (auto simp: bot_unique) next case False moreover have "(INF i:I. F i) ≠ bot" proof (cases "I = {}") case True then show ?thesis by (auto simp add: filter_eq_iff) next case False': False show ?thesis proof (rule INF_filter_not_bot) fix J assume "finite J" "J ⊆ I" then have "∃k∈I. F k ≤ (⨅i∈J. F i)" proof (induct J) case empty then show ?case using ‹I ≠ {}› by auto next case (insert i J) then obtain k where "k ∈ I" "F k ≤ (⨅i∈J. F i)" by auto with insert *[of i k] show ?case by auto qed with False show "(⨅i∈J. F i) ≠ ⊥" by (auto simp: bot_unique) qed qed ultimately show ?thesis by auto qed lemma Collect_empty_eq_bot: "Collect P = {} ⟷ P = ⊥" by auto lemma prod_filter_eq_bot: "A ×⇩_{F}B = bot ⟷ A = bot ∨ B = bot" unfolding prod_filter_def proof (subst INF_filter_bot_base; clarsimp simp: principal_eq_bot_iff Collect_empty_eq_bot bot_fun_def simp del: Collect_empty_eq) fix A1 A2 B1 B2 assume "∀⇩_{F}x in A. A1 x" "∀⇩_{F}x in A. A2 x" "∀⇩_{F}x in B. B1 x" "∀⇩_{F}x in B. B2 x" then show "∃x. eventually x A ∧ (∃y. eventually y B ∧ Collect x × Collect y ⊆ Collect A1 × Collect B1 ∧ Collect x × Collect y ⊆ Collect A2 × Collect B2)" by (intro exI[of _ "λx. A1 x ∧ A2 x"] exI[of _ "λx. B1 x ∧ B2 x"] conjI) (auto simp: eventually_conj_iff) next show "(∃x. eventually x A ∧ (∃y. eventually y B ∧ (x = (λx. False) ∨ y = (λx. False)))) = (A = ⊥ ∨ B = ⊥)" by (auto simp: trivial_limit_def intro: eventually_True) qed lemma prod_filter_mono: "F ≤ F' ⟹ G ≤ G' ⟹ F ×⇩_{F}G ≤ F' ×⇩_{F}G'" by (auto simp: le_filter_def eventually_prod_filter) lemma prod_filter_mono_iff: assumes nAB: "A ≠ bot" "B ≠ bot" shows "A ×⇩_{F}B ≤ C ×⇩_{F}D ⟷ A ≤ C ∧ B ≤ D" proof safe assume *: "A ×⇩_{F}B ≤ C ×⇩_{F}D" with assms have "A ×⇩_{F}B ≠ bot" by (auto simp: bot_unique prod_filter_eq_bot) with * have "C ×⇩_{F}D ≠ bot" by (auto simp: bot_unique) then have nCD: "C ≠ bot" "D ≠ bot" by (auto simp: prod_filter_eq_bot) show "A ≤ C" proof (rule filter_leI) fix P assume "eventually P C" with *[THEN filter_leD, of "λ(x, y). P x"] show "eventually P A" using nAB nCD by (simp add: eventually_prod1 eventually_prod2) qed show "B ≤ D" proof (rule filter_leI) fix P assume "eventually P D" with *[THEN filter_leD, of "λ(x, y). P y"] show "eventually P B" using nAB nCD by (simp add: eventually_prod1 eventually_prod2) qed qed (intro prod_filter_mono) lemma eventually_prod_same: "eventually P (F ×⇩_{F}F) ⟷ (∃Q. eventually Q F ∧ (∀x y. Q x ⟶ Q y ⟶ P (x, y)))" unfolding eventually_prod_filter apply safe apply (rule_tac x="inf Pf Pg" in exI) apply (auto simp: inf_fun_def intro!: eventually_conj) done lemma eventually_prod_sequentially: "eventually P (sequentially ×⇩_{F}sequentially) ⟷ (∃N. ∀m ≥ N. ∀n ≥ N. P (n, m))" unfolding eventually_prod_same eventually_sequentially by auto lemma principal_prod_principal: "principal A ×⇩_{F}principal B = principal (A × B)" apply (simp add: filter_eq_iff eventually_prod_filter eventually_principal) apply safe apply blast apply (intro conjI exI[of _ "λx. x ∈ A"] exI[of _ "λx. x ∈ B"]) apply auto done lemma prod_filter_INF: assumes "I ≠ {}" "J ≠ {}" shows "(INF i:I. A i) ×⇩_{F}(INF j:J. B j) = (INF i:I. INF j:J. A i ×⇩_{F}B j)" proof (safe intro!: antisym INF_greatest) from ‹I ≠ {}› obtain i where "i ∈ I" by auto from ‹J ≠ {}› obtain j where "j ∈ J" by auto show "(⨅i∈I. ⨅j∈J. A i ×⇩_{F}B j) ≤ (⨅i∈I. A i) ×⇩_{F}(⨅j∈J. B j)" unfolding prod_filter_def proof (safe intro!: INF_greatest) fix P Q assume P: "∀⇩_{F}x in ⨅i∈I. A i. P x" and Q: "∀⇩_{F}x in ⨅j∈J. B j. Q x" let ?X = "(⨅i∈I. ⨅j∈J. ⨅(P, Q)∈{(P, Q). (∀⇩_{F}x in A i. P x) ∧ (∀⇩_{F}x in B j. Q x)}. principal {(x, y). P x ∧ Q y})" have "?X ≤ principal {x. P (fst x)} ⊓ principal {x. Q (snd x)}" proof (intro inf_greatest) have "?X ≤ (⨅i∈I. ⨅P∈{P. eventually P (A i)}. principal {x. P (fst x)})" by (auto intro!: INF_greatest INF_lower2[of j] INF_lower2 ‹j∈J› INF_lower2[of "(_, λx. True)"]) also have "… ≤ principal {x. P (fst x)}" unfolding le_principal proof (rule eventually_INF_mono[OF P]) fix i P assume "i ∈ I" "eventually P (A i)" then show "∀⇩_{F}x in ⨅P∈{P. eventually P (A i)}. principal {x. P (fst x)}. x ∈ {x. P (fst x)}" unfolding le_principal[symmetric] by (auto intro!: INF_lower) qed auto finally show "?X ≤ principal {x. P (fst x)}" . have "?X ≤ (⨅i∈J. ⨅P∈{P. eventually P (B i)}. principal {x. P (snd x)})" by (auto intro!: INF_greatest INF_lower2[of i] INF_lower2 ‹i∈I› INF_lower2[of "(λx. True, _)"]) also have "… ≤ principal {x. Q (snd x)}" unfolding le_principal proof (rule eventually_INF_mono[OF Q]) fix j Q assume "j ∈ J" "eventually Q (B j)" then show "∀⇩_{F}x in ⨅P∈{P. eventually P (B j)}. principal {x. P (snd x)}. x ∈ {x. Q (snd x)}" unfolding le_principal[symmetric] by (auto intro!: INF_lower) qed auto finally show "?X ≤ principal {x. Q (snd x)}" . qed also have "… = principal {(x, y). P x ∧ Q y}" by auto finally show "?X ≤ principal {(x, y). P x ∧ Q y}" . qed qed (intro prod_filter_mono INF_lower) lemma filtermap_Pair: "filtermap (λx. (f x, g x)) F ≤ filtermap f F ×⇩_{F}filtermap g F" by (simp add: le_filter_def eventually_filtermap eventually_prod_filter) (auto elim: eventually_elim2) lemma eventually_prodI: "eventually P F ⟹ eventually Q G ⟹ eventually (λx. P (fst x) ∧ Q (snd x)) (F ×⇩_{F}G)" unfolding prod_filter_def by (intro eventually_INF1[of "(P, Q)"]) (auto simp: eventually_principal) lemma prod_filter_INF1: "I ≠ {} ⟹ (INF i:I. A i) ×⇩_{F}B = (INF i:I. A i ×⇩_{F}B)" using prod_filter_INF[of I "{B}" A "λx. x"] by simp lemma prod_filter_INF2: "J ≠ {} ⟹ A ×⇩_{F}(INF i:J. B i) = (INF i:J. A ×⇩_{F}B i)" using prod_filter_INF[of "{A}" J "λx. x" B] by simp subsection ‹Limits› definition filterlim :: "('a ⇒ 'b) ⇒ 'b filter ⇒ 'a filter ⇒ bool" where "filterlim f F2 F1 ⟷ filtermap f F1 ≤ F2" syntax "_LIM" :: "pttrns ⇒ 'a ⇒ 'b ⇒ 'a ⇒ bool" ("(3LIM (_)/ (_)./ (_) :> (_))" [1000, 10, 0, 10] 10) translations "LIM x F1. f :> F2" == "CONST filterlim (λx. f) F2 F1" lemma filterlim_top [simp]: "filterlim f top F" by (simp add: filterlim_def) lemma filterlim_iff: "(LIM x F1. f x :> F2) ⟷ (∀P. eventually P F2 ⟶ eventually (λx. P (f x)) F1)" unfolding filterlim_def le_filter_def eventually_filtermap .. lemma filterlim_compose: "filterlim g F3 F2 ⟹ filterlim f F2 F1 ⟹ filterlim (λx. g (f x)) F3 F1" unfolding filterlim_def filtermap_filtermap[symmetric] by (metis filtermap_mono order_trans) lemma filterlim_mono: "filterlim f F2 F1 ⟹ F2 ≤ F2' ⟹ F1' ≤ F1 ⟹ filterlim f F2' F1'" unfolding filterlim_def by (metis filtermap_mono order_trans) lemma filterlim_ident: "LIM x F. x :> F" by (simp add: filterlim_def filtermap_ident) lemma filterlim_cong: "F1 = F1' ⟹ F2 = F2' ⟹ eventually (λx. f x = g x) F2 ⟹ filterlim f F1 F2 = filterlim g F1' F2'" by (auto simp: filterlim_def le_filter_def eventually_filtermap elim: eventually_elim2) lemma filterlim_mono_eventually: assumes "filterlim f F G" and ord: "F ≤ F'" "G' ≤ G" assumes eq: "eventually (λx. f x = f' x) G'" shows "filterlim f' F' G'" apply (rule filterlim_cong[OF refl refl eq, THEN iffD1]) apply (rule filterlim_mono[OF _ ord]) apply fact done lemma filtermap_mono_strong: "inj f ⟹ filtermap f F ≤ filtermap f G ⟷ F ≤ G" apply (auto intro!: filtermap_mono) [] apply (auto simp: le_filter_def eventually_filtermap) apply (erule_tac x="λx. P (inv f x)" in allE) apply auto done lemma filtermap_eq_strong: "inj f ⟹ filtermap f F = filtermap f G ⟷ F = G" by (simp add: filtermap_mono_strong eq_iff) lemma filtermap_fun_inverse: assumes g: "filterlim g F G" assumes f: "filterlim f G F" assumes ev: "eventually (λx. f (g x) = x) G" shows "filtermap f F = G" proof (rule antisym) show "filtermap f F ≤ G" using f unfolding filterlim_def . have "G = filtermap f (filtermap g G)" using ev by (auto elim: eventually_elim2 simp: filter_eq_iff eventually_filtermap) also have "… ≤ filtermap f F" using g by (intro filtermap_mono) (simp add: filterlim_def) finally show "G ≤ filtermap f F" . qed lemma filterlim_principal: "(LIM x F. f x :> principal S) ⟷ (eventually (λx. f x ∈ S) F)" unfolding filterlim_def eventually_filtermap le_principal .. lemma filterlim_inf: "(LIM x F1. f x :> inf F2 F3) ⟷ ((LIM x F1. f x :> F2) ∧ (LIM x F1. f x :> F3))" unfolding filterlim_def by simp lemma filterlim_INF: "(LIM x F. f x :> (INF b:B. G b)) ⟷ (∀b∈B. LIM x F. f x :> G b)" unfolding filterlim_def le_INF_iff .. lemma filterlim_INF_INF: "(⋀m. m ∈ J ⟹ ∃i∈I. filtermap f (F i) ≤ G m) ⟹ LIM x (INF i:I. F i). f x :> (INF j:J. G j)" unfolding filterlim_def by (rule order_trans[OF filtermap_INF INF_mono]) lemma filterlim_base: "(⋀m x. m ∈ J ⟹ i m ∈ I) ⟹ (⋀m x. m ∈ J ⟹ x ∈ F (i m) ⟹ f x ∈ G m) ⟹ LIM x (INF i:I. principal (F i)). f x :> (INF j:J. principal (G j))" by (force intro!: filterlim_INF_INF simp: image_subset_iff) lemma filterlim_base_iff: assumes "I ≠ {}" and chain: "⋀i j. i ∈ I ⟹ j ∈ I ⟹ F i ⊆ F j ∨ F j ⊆ F i" shows "(LIM x (INF i:I. principal (F i)). f x :> INF j:J. principal (G j)) ⟷ (∀j∈J. ∃i∈I. ∀x∈F i. f x ∈ G j)" unfolding filterlim_INF filterlim_principal proof (subst eventually_INF_base) fix i j assume "i ∈ I" "j ∈ I" with chain[OF this] show "∃x∈I. principal (F x) ≤ inf (principal (F i)) (principal (F j))" by auto qed (auto simp: eventually_principal ‹I ≠ {}›) lemma filterlim_filtermap: "filterlim f F1 (filtermap g F2) = filterlim (λx. f (g x)) F1 F2" unfolding filterlim_def filtermap_filtermap .. lemma filterlim_sup: "filterlim f F F1 ⟹ filterlim f F F2 ⟹ filterlim f F (sup F1 F2)" unfolding filterlim_def filtermap_sup by auto lemma filterlim_sequentially_Suc: "(LIM x sequentially. f (Suc x) :> F) ⟷ (LIM x sequentially. f x :> F)" unfolding filterlim_iff by (subst eventually_sequentially_Suc) simp lemma filterlim_Suc: "filterlim Suc sequentially sequentially" by (simp add: filterlim_iff eventually_sequentially) lemma filterlim_If: "LIM x inf F (principal {x. P x}). f x :> G ⟹ LIM x inf F (principal {x. ¬ P x}). g x :> G ⟹ LIM x F. if P x then f x else g x :> G" unfolding filterlim_iff eventually_inf_principal by (auto simp: eventually_conj_iff) lemma filterlim_Pair: "LIM x F. f x :> G ⟹ LIM x F. g x :> H ⟹ LIM x F. (f x, g x) :> G ×⇩_{F}H" unfolding filterlim_def by (rule order_trans[OF filtermap_Pair prod_filter_mono]) subsection ‹Limits to @{const at_top} and @{const at_bot}› lemma filterlim_at_top: fixes f :: "'a ⇒ ('b::linorder)" shows "(LIM x F. f x :> at_top) ⟷ (∀Z. eventually (λx. Z ≤ f x) F)" by (auto simp: filterlim_iff eventually_at_top_linorder elim!: eventually_mono) lemma filterlim_at_top_mono: "LIM x F. f x :> at_top ⟹ eventually (λx. f x ≤ (g x::'a::linorder)) F ⟹ LIM x F. g x :> at_top" by (auto simp: filterlim_at_top elim: eventually_elim2 intro: order_trans) lemma filterlim_at_top_dense: fixes f :: "'a ⇒ ('b::unbounded_dense_linorder)" shows "(LIM x F. f x :> at_top) ⟷ (∀Z. eventually (λx. Z < f x) F)" by (metis eventually_mono[of _ F] eventually_gt_at_top order_less_imp_le filterlim_at_top[of f F] filterlim_iff[of f at_top F]) lemma filterlim_at_top_ge: fixes f :: "'a ⇒ ('b::linorder)" and c :: "'b" shows "(LIM x F. f x :> at_top) ⟷ (∀Z≥c. eventually (λx. Z ≤ f x) F)" unfolding at_top_sub[of c] filterlim_INF by (auto simp add: filterlim_principal) lemma filterlim_at_top_at_top: fixes f :: "'a::linorder ⇒ 'b::linorder" assumes mono: "⋀x y. Q x ⟹ Q y ⟹ x ≤ y ⟹ f x ≤ f y" assumes bij: "⋀x. P x ⟹ f (g x) = x" "⋀x. P x ⟹ Q (g x)" assumes Q: "eventually Q at_top" assumes P: "eventually P at_top" shows "filterlim f at_top at_top" proof - from P obtain x where x: "⋀y. x ≤ y ⟹ P y" unfolding eventually_at_top_linorder by auto show ?thesis proof (intro filterlim_at_top_ge[THEN iffD2] allI impI) fix z assume "x ≤ z" with x have "P z" by auto have "eventually (λx. g z ≤ x) at_top" by (rule eventually_ge_at_top) with Q show "eventually (λx. z ≤ f x) at_top" by eventually_elim (metis mono bij ‹P z›) qed qed lemma filterlim_at_top_gt: fixes f :: "'a ⇒ ('b::unbounded_dense_linorder)" and c :: "'b" shows "(LIM x F. f x :> at_top) ⟷ (∀Z>c. eventually (λx. Z ≤ f x) F)" by (metis filterlim_at_top order_less_le_trans gt_ex filterlim_at_top_ge) lemma filterlim_at_bot: fixes f :: "'a ⇒ ('b::linorder)" shows "(LIM x F. f x :> at_bot) ⟷ (∀Z. eventually (λx. f x ≤ Z) F)" by (auto simp: filterlim_iff eventually_at_bot_linorder elim!: eventually_mono) lemma filterlim_at_bot_dense: fixes f :: "'a ⇒ ('b::{dense_linorder, no_bot})" shows "(LIM x F. f x :> at_bot) ⟷ (∀Z. eventually (λx. f x < Z) F)" proof (auto simp add: filterlim_at_bot[of f F]) fix Z :: 'b from lt_ex [of Z] obtain Z' where 1: "Z' < Z" .. assume "∀Z. eventually (λx. f x ≤ Z) F" hence "eventually (λx. f x ≤ Z') F" by auto thus "eventually (λx. f x < Z) F" apply (rule eventually_mono) using 1 by auto next fix Z :: 'b show "∀Z. eventually (λx. f x < Z) F ⟹ eventually (λx. f x ≤ Z) F" by (drule spec [of _ Z], erule eventually_mono, auto simp add: less_imp_le) qed lemma filterlim_at_bot_le: fixes f :: "'a ⇒ ('b::linorder)" and c :: "'b" shows "(LIM x F. f x :> at_bot) ⟷ (∀Z≤c. eventually (λx. Z ≥ f x) F)" unfolding filterlim_at_bot proof safe fix Z assume *: "∀Z≤c. eventually (λx. Z ≥ f x) F" with *[THEN spec, of "min Z c"] show "eventually (λx. Z ≥ f x) F" by (auto elim!: eventually_mono) qed simp lemma filterlim_at_bot_lt: fixes f :: "'a ⇒ ('b::unbounded_dense_linorder)" and c :: "'b" shows "(LIM x F. f x :> at_bot) ⟷ (∀Z<c. eventually (λx. Z ≥ f x) F)" by (metis filterlim_at_bot filterlim_at_bot_le lt_ex order_le_less_trans) lemma filterlim_filtercomap [intro]: "filterlim f F (filtercomap f F)" unfolding filterlim_def by (rule filtermap_filtercomap) subsection ‹Setup @{typ "'a filter"} for lifting and transfer› context includes lifting_syntax begin definition rel_filter :: "('a ⇒ 'b ⇒ bool) ⇒ 'a filter ⇒ 'b filter ⇒ bool" where "rel_filter R F G = ((R ===> op =) ===> op =) (Rep_filter F) (Rep_filter G)" lemma rel_filter_eventually: "rel_filter R F G ⟷ ((R ===> op =) ===> op =) (λP. eventually P F) (λP. eventually P G)" by(simp add: rel_filter_def eventually_def) lemma filtermap_id [simp, id_simps]: "filtermap id = id" by(simp add: fun_eq_iff id_def filtermap_ident) lemma filtermap_id' [simp]: "filtermap (λx. x) = (λF. F)" using filtermap_id unfolding id_def . lemma Quotient_filter [quot_map]: assumes Q: "Quotient R Abs Rep T" shows "Quotient (rel_filter R) (filtermap Abs) (filtermap Rep) (rel_filter T)" unfolding Quotient_alt_def proof(intro conjI strip) from Q have *: "⋀x y. T x y ⟹ Abs x = y" unfolding Quotient_alt_def by blast fix F G assume "rel_filter T F G" thus "filtermap Abs F = G" unfolding filter_eq_iff by(auto simp add: eventually_filtermap rel_filter_eventually * rel_funI del: iffI elim!: rel_funD) next from Q have *: "⋀x. T (Rep x) x" unfolding Quotient_alt_def by blast fix F show "rel_filter T (filtermap Rep F) F" by(auto elim: rel_funD intro: * intro!: ext arg_cong[where f="λP. eventually P F"] rel_funI del: iffI simp add: eventually_filtermap rel_filter_eventually) qed(auto simp add: map_fun_def o_def eventually_filtermap filter_eq_iff fun_eq_iff rel_filter_eventually fun_quotient[OF fun_quotient[OF Q identity_quotient] identity_quotient, unfolded Quotient_alt_def]) lemma eventually_parametric [transfer_rule]: "((A ===> op =) ===> rel_filter A ===> op =) eventually eventually" by(simp add: rel_fun_def rel_filter_eventually) lemma frequently_parametric [transfer_rule]: "((A ===> op =) ===> rel_filter A ===> op =) frequently frequently" unfolding frequently_def[abs_def] by transfer_prover lemma rel_filter_eq [relator_eq]: "rel_filter op = = op =" by(auto simp add: rel_filter_eventually rel_fun_eq fun_eq_iff filter_eq_iff) lemma rel_filter_mono [relator_mono]: "A ≤ B ⟹ rel_filter A ≤ rel_filter B" unfolding rel_filter_eventually[abs_def] by(rule le_funI)+(intro fun_mono fun_mono[THEN le_funD, THEN le_funD] order.refl) lemma rel_filter_conversep [simp]: "rel_filter A¯¯ = (rel_filter A)¯¯" apply (simp add: rel_filter_eventually fun_eq_iff rel_fun_def) apply (safe; metis) done lemma is_filter_parametric_aux: assumes "is_filter F" assumes [transfer_rule]: "bi_total A" "bi_unique A" and [transfer_rule]: "((A ===> op =) ===> op =) F G" shows "is_filter G" proof - interpret is_filter F by fact show ?thesis proof have "F (λ_. True) = G (λx. True)" by transfer_prover thus "G (λx. True)" by(simp add: True) next fix P' Q' assume "G P'" "G Q'" moreover from bi_total_fun[OF ‹bi_unique A› bi_total_eq, unfolded bi_total_def] obtain P Q where [transfer_rule]: "(A ===> op =) P P'" "(A ===> op =) Q Q'" by blast have "F P = G P'" "F Q = G Q'" by transfer_prover+ ultimately have "F (λx. P x ∧ Q x)" by(simp add: conj) moreover have "F (λx. P x ∧ Q x) = G (λx. P' x ∧ Q' x)" by transfer_prover ultimately show "G (λx. P' x ∧ Q' x)" by simp next fix P' Q' assume "∀x. P' x ⟶ Q' x" "G P'" moreover from bi_total_fun[OF ‹bi_unique A› bi_total_eq, unfolded bi_total_def] obtain P Q where [transfer_rule]: "(A ===> op =) P P'" "(A ===> op =) Q Q'" by blast have "F P = G P'" by transfer_prover moreover have "(∀x. P x ⟶ Q x) ⟷ (∀x. P' x ⟶ Q' x)" by transfer_prover ultimately have "F Q" by(simp add: mono) moreover have "F Q = G Q'" by transfer_prover ultimately show "G Q'" by simp qed qed lemma is_filter_parametric [transfer_rule]: "⟦ bi_total A; bi_unique A ⟧ ⟹ (((A ===> op =) ===> op =) ===> op =) is_filter is_filter" apply(rule rel_funI) apply(rule iffI) apply(erule (3) is_filter_parametric_aux) apply(erule is_filter_parametric_aux[where A="conversep A"]) apply (simp_all add: rel_fun_def) apply metis done lemma left_total_rel_filter [transfer_rule]: assumes [transfer_rule]: "bi_total A" "bi_unique A" shows "left_total (rel_filter A)" proof(rule left_totalI) fix F :: "'a filter" from bi_total_fun[OF bi_unique_fun[OF ‹bi_total A› bi_unique_eq] bi_total_eq] obtain G where [transfer_rule]: "((A ===> op =) ===> op =) (λP. eventually P F) G" unfolding bi_total_def by blast moreover have "is_filter (λP. eventually P F) ⟷ is_filter G" by transfer_prover hence "is_filter G" by(simp add: eventually_def is_filter_Rep_filter) ultimately have "rel_filter A F (Abs_filter G)" by(simp add: rel_filter_eventually eventually_Abs_filter) thus "∃G. rel_filter A F G" .. qed lemma right_total_rel_filter [transfer_rule]: "⟦ bi_total A; bi_unique A ⟧ ⟹ right_total (rel_filter A)" using left_total_rel_filter[of "A¯¯"] by simp lemma bi_total_rel_filter [transfer_rule]: assumes "bi_total A" "bi_unique A" shows "bi_total (rel_filter A)" unfolding bi_total_alt_def using assms by(simp add: left_total_rel_filter right_total_rel_filter) lemma left_unique_rel_filter [transfer_rule]: assumes "left_unique A" shows "left_unique (rel_filter A)" proof(rule left_uniqueI) fix F F' G assume [transfer_rule]: "rel_filter A F G" "rel_filter A F' G" show "F = F'" unfolding filter_eq_iff proof fix P :: "'a ⇒ bool" obtain P' where [transfer_rule]: "(A ===> op =) P P'" using left_total_fun[OF assms left_total_eq] unfolding left_total_def by blast have "eventually P F = eventually P' G" and "eventually P F' = eventually P' G" by transfer_prover+ thus "eventually P F = eventually P F'" by simp qed qed lemma right_unique_rel_filter [transfer_rule]: "right_unique A ⟹ right_unique (rel_filter A)" using left_unique_rel_filter[of "A¯¯"] by simp lemma bi_unique_rel_filter [transfer_rule]: "bi_unique A ⟹ bi_unique (rel_filter A)" by(simp add: bi_unique_alt_def left_unique_rel_filter right_unique_rel_filter) lemma top_filter_parametric [transfer_rule]: "bi_total A ⟹ (rel_filter A) top top" by(simp add: rel_filter_eventually All_transfer) lemma bot_filter_parametric [transfer_rule]: "(rel_filter A) bot bot" by(simp add: rel_filter_eventually rel_fun_def) lemma sup_filter_parametric [transfer_rule]: "(rel_filter A ===> rel_filter A ===> rel_filter A) sup sup" by(fastforce simp add: rel_filter_eventually[abs_def] eventually_sup dest: rel_funD) lemma Sup_filter_parametric [transfer_rule]: "(rel_set (rel_filter A) ===> rel_filter A) Sup Sup" proof(rule rel_funI) fix S T assume [transfer_rule]: "rel_set (rel_filter A) S T" show "rel_filter A (Sup S) (Sup T)" by(simp add: rel_filter_eventually eventually_Sup) transfer_prover qed lemma principal_parametric [transfer_rule]: "(rel_set A ===> rel_filter A) principal principal" proof(rule rel_funI) fix S S' assume [transfer_rule]: "rel_set A S S'" show "rel_filter A (principal S) (principal S')" by(simp add: rel_filter_eventually eventually_principal) transfer_prover qed lemma filtermap_parametric [transfer_rule]: "((A ===> B) ===> rel_filter A ===> rel_filter B) filtermap filtermap" proof (intro rel_funI) fix f g F G assume [transfer_rule]: "(A ===> B) f g" "rel_filter A F G" show "rel_filter B (filtermap f F) (filtermap g G)" unfolding rel_filter_eventually eventually_filtermap by transfer_prover qed (* TODO: Are those assumptions needed? *) lemma filtercomap_parametric [transfer_rule]: assumes [transfer_rule]: "bi_unique B" "bi_total A" shows "((A ===> B) ===> rel_filter B ===> rel_filter A) filtercomap filtercomap" proof (intro rel_funI) fix f g F G assume [transfer_rule]: "(A ===> B) f g" "rel_filter B F G" show "rel_filter A (filtercomap f F) (filtercomap g G)" unfolding rel_filter_eventually eventually_filtercomap by transfer_prover qed context fixes A :: "'a ⇒ 'b ⇒ bool" assumes [transfer_rule]: "bi_unique A" begin lemma le_filter_parametric [transfer_rule]: "(rel_filter A ===> rel_filter A ===> op =) op ≤ op ≤" unfolding le_filter_def[abs_def] by transfer_prover lemma less_filter_parametric [transfer_rule]: "(rel_filter A ===> rel_filter A ===> op =) op < op <" unfolding less_filter_def[abs_def] by transfer_prover context assumes [transfer_rule]: "bi_total A" begin lemma Inf_filter_parametric [transfer_rule]: "(rel_set (rel_filter A) ===> rel_filter A) Inf Inf" unfolding Inf_filter_def[abs_def] by transfer_prover lemma inf_filter_parametric [transfer_rule]: "(rel_filter A ===> rel_filter A ===> rel_filter A) inf inf" proof(intro rel_funI)+ fix F F' G G' assume [transfer_rule]: "rel_filter A F F'" "rel_filter A G G'" have "rel_filter A (Inf {F, G}) (Inf {F', G'})" by transfer_prover thus "rel_filter A (inf F G) (inf F' G')" by simp qed end end end text ‹Code generation for filters› definition abstract_filter :: "(unit ⇒ 'a filter) ⇒ 'a filter" where [simp]: "abstract_filter f = f ()" code_datatype principal abstract_filter hide_const (open) abstract_filter declare [[code drop: filterlim prod_filter filtermap eventually "inf :: _ filter ⇒ _" "sup :: _ filter ⇒ _" "less_eq :: _ filter ⇒ _" Abs_filter]] declare filterlim_principal [code] declare principal_prod_principal [code] declare filtermap_principal [code] declare filtercomap_principal [code] declare eventually_principal [code] declare inf_principal [code] declare sup_principal [code] declare principal_le_iff [code] lemma Rep_filter_iff_eventually [simp, code]: "Rep_filter F P ⟷ eventually P F" by (simp add: eventually_def) lemma bot_eq_principal_empty [code]: "bot = principal {}" by simp lemma top_eq_principal_UNIV [code]: "top = principal UNIV" by simp instantiation filter :: (equal) equal begin definition equal_filter :: "'a filter ⇒ 'a filter ⇒ bool" where "equal_filter F F' ⟷ F = F'" lemma equal_filter [code]: "HOL.equal (principal A) (principal B) ⟷ A = B" by (simp add: equal_filter_def) instance by standard (simp add: equal_filter_def) end end