1 (* Title: HOL/Finite_Set.thy
2 Author: Tobias Nipkow, Lawrence C Paulson and Markus Wenzel
3 with contributions by Jeremy Avigad
6 header {* Finite sets *}
12 subsection {* Predicate for finite sets *}
14 inductive finite :: "'a set \<Rightarrow> bool"
16 emptyI [simp, intro!]: "finite {}"
17 | insertI [simp, intro!]: "finite A \<Longrightarrow> finite (insert a A)"
19 lemma finite_induct [case_names empty insert, induct set: finite]:
20 -- {* Discharging @{text "x \<notin> F"} entails extra work. *}
23 and insert: "\<And>x F. finite F \<Longrightarrow> x \<notin> F \<Longrightarrow> P F \<Longrightarrow> P (insert x F)"
25 using `finite F` proof induct
27 fix x F assume F: "finite F" and P: "P F"
31 hence "insert x F = F" by (rule insert_absorb)
32 with P show ?thesis by (simp only:)
35 from F this P show ?thesis by (rule insert)
40 subsubsection {* Choice principles *}
42 lemma ex_new_if_finite: -- "does not depend on def of finite at all"
43 assumes "\<not> finite (UNIV :: 'a set)" and "finite A"
44 shows "\<exists>a::'a. a \<notin> A"
46 from assms have "A \<noteq> UNIV" by blast
47 then show ?thesis by blast
50 text {* A finite choice principle. Does not need the SOME choice operator. *}
52 lemma finite_set_choice:
53 "finite A \<Longrightarrow> \<forall>x\<in>A. \<exists>y. P x y \<Longrightarrow> \<exists>f. \<forall>x\<in>A. P x (f x)"
54 proof (induct rule: finite_induct)
55 case empty then show ?case by simp
58 then obtain f b where f: "ALL x:A. P x (f x)" and ab: "P a b" by auto
59 show ?case (is "EX f. ?P f")
61 show "?P(%x. if x = a then b else f x)" using f ab by auto
66 subsubsection {* Finite sets are the images of initial segments of natural numbers *}
68 lemma finite_imp_nat_seg_image_inj_on:
70 shows "\<exists>(n::nat) f. A = f ` {i. i < n} \<and> inj_on f {i. i < n}"
71 using assms proof induct
75 show "\<exists>f. {} = f ` {i::nat. i < 0} \<and> inj_on f {i. i < 0}" by simp
79 have notinA: "a \<notin> A" by fact
80 from insert.hyps obtain n f
81 where "A = f ` {i::nat. i < n}" "inj_on f {i. i < n}" by blast
82 hence "insert a A = f(n:=a) ` {i. i < Suc n}"
83 "inj_on (f(n:=a)) {i. i < Suc n}" using notinA
84 by (auto simp add: image_def Ball_def inj_on_def less_Suc_eq)
88 lemma nat_seg_image_imp_finite:
89 "A = f ` {i::nat. i < n} \<Longrightarrow> finite A"
90 proof (induct n arbitrary: A)
91 case 0 thus ?case by simp
94 let ?B = "f ` {i. i < n}"
95 have finB: "finite ?B" by(rule Suc.hyps[OF refl])
98 assume "\<exists>k<n. f n = f k"
99 hence "A = ?B" using Suc.prems by(auto simp:less_Suc_eq)
100 thus ?thesis using finB by simp
102 assume "\<not>(\<exists> k<n. f n = f k)"
103 hence "A = insert (f n) ?B" using Suc.prems by(auto simp:less_Suc_eq)
104 thus ?thesis using finB by simp
108 lemma finite_conv_nat_seg_image:
109 "finite A \<longleftrightarrow> (\<exists>(n::nat) f. A = f ` {i::nat. i < n})"
110 by (blast intro: nat_seg_image_imp_finite dest: finite_imp_nat_seg_image_inj_on)
112 lemma finite_imp_inj_to_nat_seg:
114 shows "\<exists>f n::nat. f ` A = {i. i < n} \<and> inj_on f A"
116 from finite_imp_nat_seg_image_inj_on[OF `finite A`]
117 obtain f and n::nat where bij: "bij_betw f {i. i<n} A"
118 by (auto simp:bij_betw_def)
119 let ?f = "the_inv_into {i. i<n} f"
120 have "inj_on ?f A & ?f ` A = {i. i<n}"
121 by (fold bij_betw_def) (rule bij_betw_the_inv_into[OF bij])
122 thus ?thesis by blast
125 lemma finite_Collect_less_nat [iff]:
126 "finite {n::nat. n < k}"
127 by (fastsimp simp: finite_conv_nat_seg_image)
129 lemma finite_Collect_le_nat [iff]:
130 "finite {n::nat. n \<le> k}"
131 by (simp add: le_eq_less_or_eq Collect_disj_eq)
134 subsubsection {* Finiteness and common set operations *}
136 lemma rev_finite_subset:
137 "finite B \<Longrightarrow> A \<subseteq> B \<Longrightarrow> finite A"
138 proof (induct arbitrary: A rule: finite_induct)
140 then show ?case by simp
143 have A: "A \<subseteq> insert x F" and r: "A - {x} \<subseteq> F \<Longrightarrow> finite (A - {x})" by fact+
146 assume x: "x \<in> A"
147 with A have "A - {x} \<subseteq> F" by (simp add: subset_insert_iff)
148 with r have "finite (A - {x})" .
149 hence "finite (insert x (A - {x}))" ..
150 also have "insert x (A - {x}) = A" using x by (rule insert_Diff)
151 finally show ?thesis .
153 show "A \<subseteq> F ==> ?thesis" by fact
154 assume "x \<notin> A"
155 with A show "A \<subseteq> F" by (simp add: subset_insert_iff)
160 "A \<subseteq> B \<Longrightarrow> finite B \<Longrightarrow> finite A"
161 by (rule rev_finite_subset)
164 assumes "finite F" and "finite G"
165 shows "finite (F \<union> G)"
166 using assms by induct simp_all
168 lemma finite_Un [iff]:
169 "finite (F \<union> G) \<longleftrightarrow> finite F \<and> finite G"
170 by (blast intro: finite_UnI finite_subset [of _ "F \<union> G"])
172 lemma finite_insert [simp]: "finite (insert a A) \<longleftrightarrow> finite A"
174 have "finite {a} \<and> finite A \<longleftrightarrow> finite A" by simp
175 then have "finite ({a} \<union> A) \<longleftrightarrow> finite A" by (simp only: finite_Un)
176 then show ?thesis by simp
179 lemma finite_Int [simp, intro]:
180 "finite F \<or> finite G \<Longrightarrow> finite (F \<inter> G)"
181 by (blast intro: finite_subset)
183 lemma finite_Collect_conjI [simp, intro]:
184 "finite {x. P x} \<or> finite {x. Q x} \<Longrightarrow> finite {x. P x \<and> Q x}"
185 by (simp add: Collect_conj_eq)
187 lemma finite_Collect_disjI [simp]:
188 "finite {x. P x \<or> Q x} \<longleftrightarrow> finite {x. P x} \<and> finite {x. Q x}"
189 by (simp add: Collect_disj_eq)
191 lemma finite_Diff [simp, intro]:
192 "finite A \<Longrightarrow> finite (A - B)"
193 by (rule finite_subset, rule Diff_subset)
195 lemma finite_Diff2 [simp]:
197 shows "finite (A - B) \<longleftrightarrow> finite A"
199 have "finite A \<longleftrightarrow> finite((A - B) \<union> (A \<inter> B))" by (simp add: Un_Diff_Int)
200 also have "\<dots> \<longleftrightarrow> finite (A - B)" using `finite B` by simp
201 finally show ?thesis ..
204 lemma finite_Diff_insert [iff]:
205 "finite (A - insert a B) \<longleftrightarrow> finite (A - B)"
207 have "finite (A - B) \<longleftrightarrow> finite (A - B - {a})" by simp
208 moreover have "A - insert a B = A - B - {a}" by auto
209 ultimately show ?thesis by simp
212 lemma finite_compl[simp]:
213 "finite (A :: 'a set) \<Longrightarrow> finite (- A) \<longleftrightarrow> finite (UNIV :: 'a set)"
214 by (simp add: Compl_eq_Diff_UNIV)
216 lemma finite_Collect_not[simp]:
217 "finite {x :: 'a. P x} \<Longrightarrow> finite {x. \<not> P x} \<longleftrightarrow> finite (UNIV :: 'a set)"
218 by (simp add: Collect_neg_eq)
220 lemma finite_Union [simp, intro]:
221 "finite A \<Longrightarrow> (\<And>M. M \<in> A \<Longrightarrow> finite M) \<Longrightarrow> finite(\<Union>A)"
222 by (induct rule: finite_induct) simp_all
224 lemma finite_UN_I [intro]:
225 "finite A \<Longrightarrow> (\<And>a. a \<in> A \<Longrightarrow> finite (B a)) \<Longrightarrow> finite (\<Union>a\<in>A. B a)"
226 by (induct rule: finite_induct) simp_all
228 lemma finite_UN [simp]:
229 "finite A \<Longrightarrow> finite (UNION A B) \<longleftrightarrow> (\<forall>x\<in>A. finite (B x))"
230 by (blast intro: finite_subset)
232 lemma finite_Inter [intro]:
233 "\<exists>A\<in>M. finite A \<Longrightarrow> finite (\<Inter>M)"
234 by (blast intro: Inter_lower finite_subset)
236 lemma finite_INT [intro]:
237 "\<exists>x\<in>I. finite (A x) \<Longrightarrow> finite (\<Inter>x\<in>I. A x)"
238 by (blast intro: INT_lower finite_subset)
240 lemma finite_imageI [simp, intro]:
241 "finite F \<Longrightarrow> finite (h ` F)"
242 by (induct rule: finite_induct) simp_all
244 lemma finite_image_set [simp]:
245 "finite {x. P x} \<Longrightarrow> finite { f x | x. P x }"
246 by (simp add: image_Collect [symmetric])
249 assumes "finite (f ` A)" and "inj_on f A"
251 using assms proof (induct "f ` A" arbitrary: A)
252 case empty then show ?case by simp
255 then have B_A: "insert x B = f ` A" by simp
256 then obtain y where "x = f y" and "y \<in> A" by blast
257 from B_A `x \<notin> B` have "B = f ` A - {x}" by blast
258 with B_A `x \<notin> B` `x = f y` `inj_on f A` `y \<in> A` have "B = f ` (A - {y})" by (simp add: inj_on_image_set_diff)
259 moreover from `inj_on f A` have "inj_on f (A - {y})" by (rule inj_on_diff)
260 ultimately have "finite (A - {y})" by (rule insert.hyps)
261 then show "finite A" by simp
265 "finite A \<Longrightarrow> B \<subseteq> f ` A \<Longrightarrow> finite B"
266 by (erule finite_subset) (rule finite_imageI)
268 lemma finite_range_imageI:
269 "finite (range g) \<Longrightarrow> finite (range (\<lambda>x. f (g x)))"
270 by (drule finite_imageI) (simp add: range_composition)
272 lemma finite_subset_image:
274 shows "B \<subseteq> f ` A \<Longrightarrow> \<exists>C\<subseteq>A. finite C \<and> B = f ` C"
275 using assms proof induct
276 case empty then show ?case by simp
278 case insert then show ?case
279 by (clarsimp simp del: image_insert simp add: image_insert [symmetric])
283 lemma finite_vimageI:
284 "finite F \<Longrightarrow> inj h \<Longrightarrow> finite (h -` F)"
285 apply (induct rule: finite_induct)
287 apply (subst vimage_insert)
288 apply (simp add: finite_subset [OF inj_vimage_singleton])
291 lemma finite_vimageD:
292 assumes fin: "finite (h -` F)" and surj: "surj h"
295 have "finite (h ` (h -` F))" using fin by (rule finite_imageI)
296 also have "h ` (h -` F) = F" using surj by (rule surj_image_vimage_eq)
297 finally show "finite F" .
300 lemma finite_vimage_iff: "bij h \<Longrightarrow> finite (h -` F) \<longleftrightarrow> finite F"
301 unfolding bij_def by (auto elim: finite_vimageD finite_vimageI)
303 lemma finite_Collect_bex [simp]:
305 shows "finite {x. \<exists>y\<in>A. Q x y} \<longleftrightarrow> (\<forall>y\<in>A. finite {x. Q x y})"
307 have "{x. \<exists>y\<in>A. Q x y} = (\<Union>y\<in>A. {x. Q x y})" by auto
308 with assms show ?thesis by simp
311 lemma finite_Collect_bounded_ex [simp]:
312 assumes "finite {y. P y}"
313 shows "finite {x. \<exists>y. P y \<and> Q x y} \<longleftrightarrow> (\<forall>y. P y \<longrightarrow> finite {x. Q x y})"
315 have "{x. EX y. P y & Q x y} = (\<Union>y\<in>{y. P y}. {x. Q x y})" by auto
316 with assms show ?thesis by simp
320 "finite A \<Longrightarrow> finite B \<Longrightarrow> finite (A <+> B)"
321 by (simp add: Plus_def)
324 fixes A :: "'a set" and B :: "'b set"
325 assumes fin: "finite (A <+> B)"
326 shows "finite A" "finite B"
328 have "Inl ` A \<subseteq> A <+> B" by auto
329 then have "finite (Inl ` A :: ('a + 'b) set)" using fin by (rule finite_subset)
330 then show "finite A" by (rule finite_imageD) (auto intro: inj_onI)
332 have "Inr ` B \<subseteq> A <+> B" by auto
333 then have "finite (Inr ` B :: ('a + 'b) set)" using fin by (rule finite_subset)
334 then show "finite B" by (rule finite_imageD) (auto intro: inj_onI)
337 lemma finite_Plus_iff [simp]:
338 "finite (A <+> B) \<longleftrightarrow> finite A \<and> finite B"
339 by (auto intro: finite_PlusD finite_Plus)
341 lemma finite_Plus_UNIV_iff [simp]:
342 "finite (UNIV :: ('a + 'b) set) \<longleftrightarrow> finite (UNIV :: 'a set) \<and> finite (UNIV :: 'b set)"
343 by (subst UNIV_Plus_UNIV [symmetric]) (rule finite_Plus_iff)
345 lemma finite_SigmaI [simp, intro]:
346 "finite A \<Longrightarrow> (\<And>a. a\<in>A \<Longrightarrow> finite (B a)) ==> finite (SIGMA a:A. B a)"
347 by (unfold Sigma_def) blast
349 lemma finite_cartesian_product:
350 "finite A \<Longrightarrow> finite B \<Longrightarrow> finite (A \<times> B)"
351 by (rule finite_SigmaI)
353 lemma finite_Prod_UNIV:
354 "finite (UNIV :: 'a set) \<Longrightarrow> finite (UNIV :: 'b set) \<Longrightarrow> finite (UNIV :: ('a \<times> 'b) set)"
355 by (simp only: UNIV_Times_UNIV [symmetric] finite_cartesian_product)
357 lemma finite_cartesian_productD1:
358 assumes "finite (A \<times> B)" and "B \<noteq> {}"
361 from assms obtain n f where "A \<times> B = f ` {i::nat. i < n}"
362 by (auto simp add: finite_conv_nat_seg_image)
363 then have "fst ` (A \<times> B) = fst ` f ` {i::nat. i < n}" by simp
364 with `B \<noteq> {}` have "A = (fst \<circ> f) ` {i::nat. i < n}"
365 by (simp add: image_compose)
366 then have "\<exists>n f. A = f ` {i::nat. i < n}" by blast
368 by (auto simp add: finite_conv_nat_seg_image)
371 lemma finite_cartesian_productD2:
372 assumes "finite (A \<times> B)" and "A \<noteq> {}"
375 from assms obtain n f where "A \<times> B = f ` {i::nat. i < n}"
376 by (auto simp add: finite_conv_nat_seg_image)
377 then have "snd ` (A \<times> B) = snd ` f ` {i::nat. i < n}" by simp
378 with `A \<noteq> {}` have "B = (snd \<circ> f) ` {i::nat. i < n}"
379 by (simp add: image_compose)
380 then have "\<exists>n f. B = f ` {i::nat. i < n}" by blast
382 by (auto simp add: finite_conv_nat_seg_image)
385 lemma finite_Pow_iff [iff]:
386 "finite (Pow A) \<longleftrightarrow> finite A"
388 assume "finite (Pow A)"
389 then have "finite ((%x. {x}) ` A)" by (blast intro: finite_subset)
390 then show "finite A" by (rule finite_imageD [unfolded inj_on_def]) simp
393 then show "finite (Pow A)"
394 by induct (simp_all add: Pow_insert)
397 corollary finite_Collect_subsets [simp, intro]:
398 "finite A \<Longrightarrow> finite {B. B \<subseteq> A}"
399 by (simp add: Pow_def [symmetric])
401 lemma finite_UnionD: "finite(\<Union>A) \<Longrightarrow> finite A"
402 by (blast intro: finite_subset [OF subset_Pow_Union])
405 subsubsection {* Further induction rules on finite sets *}
407 lemma finite_ne_induct [case_names singleton insert, consumes 2]:
408 assumes "finite F" and "F \<noteq> {}"
409 assumes "\<And>x. P {x}"
410 and "\<And>x F. finite F \<Longrightarrow> F \<noteq> {} \<Longrightarrow> x \<notin> F \<Longrightarrow> P F \<Longrightarrow> P (insert x F)"
412 using assms proof induct
413 case empty then show ?case by simp
415 case (insert x F) then show ?case by cases auto
418 lemma finite_subset_induct [consumes 2, case_names empty insert]:
419 assumes "finite F" and "F \<subseteq> A"
420 assumes empty: "P {}"
421 and insert: "\<And>a F. finite F \<Longrightarrow> a \<in> A \<Longrightarrow> a \<notin> F \<Longrightarrow> P F \<Longrightarrow> P (insert a F)"
423 using `finite F` `F \<subseteq> A` proof induct
427 assume "finite F" and "x \<notin> F" and
428 P: "F \<subseteq> A \<Longrightarrow> P F" and i: "insert x F \<subseteq> A"
429 show "P (insert x F)"
431 from i show "x \<in> A" by blast
432 from i have "F \<subseteq> A" by blast
434 show "finite F" by fact
435 show "x \<notin> F" by fact
439 lemma finite_empty_induct:
442 and remove: "\<And>a A. finite A \<Longrightarrow> a \<in> A \<Longrightarrow> P A \<Longrightarrow> P (A - {a})"
445 have "\<And>B. B \<subseteq> A \<Longrightarrow> P (A - B)"
448 assume "B \<subseteq> A"
449 with `finite A` have "finite B" by (rule rev_finite_subset)
450 from this `B \<subseteq> A` show "P (A - B)"
453 from `P A` show ?case by simp
456 have "P (A - B - {b})"
458 from `finite A` show "finite (A - B)" by induct auto
459 from insert show "b \<in> A - B" by simp
460 from insert show "P (A - B)" by simp
462 also have "A - B - {b} = A - insert b B" by (rule Diff_insert [symmetric])
466 then have "P (A - A)" by blast
467 then show ?thesis by simp
471 subsection {* Class @{text finite} *}
474 assumes finite_UNIV: "finite (UNIV \<Colon> 'a set)"
477 lemma finite [simp]: "finite (A \<Colon> 'a set)"
478 by (rule subset_UNIV finite_UNIV finite_subset)+
480 lemma finite_code [code]: "finite (A \<Colon> 'a set) = True"
485 lemma UNIV_unit [no_atp]:
486 "UNIV = {()}" by auto
488 instance unit :: finite proof
489 qed (simp add: UNIV_unit)
491 lemma UNIV_bool [no_atp]:
492 "UNIV = {False, True}" by auto
494 instance bool :: finite proof
495 qed (simp add: UNIV_bool)
497 instance prod :: (finite, finite) finite proof
498 qed (simp only: UNIV_Times_UNIV [symmetric] finite_cartesian_product finite)
500 lemma finite_option_UNIV [simp]:
501 "finite (UNIV :: 'a option set) = finite (UNIV :: 'a set)"
502 by (auto simp add: UNIV_option_conv elim: finite_imageD intro: inj_Some)
504 instance option :: (finite) finite proof
505 qed (simp add: UNIV_option_conv)
507 lemma inj_graph: "inj (%f. {(x, y). y = f x})"
508 by (rule inj_onI, auto simp add: set_eq_iff fun_eq_iff)
510 instance "fun" :: (finite, finite) finite
512 show "finite (UNIV :: ('a => 'b) set)"
513 proof (rule finite_imageD)
514 let ?graph = "%f::'a => 'b. {(x, y). y = f x}"
515 have "range ?graph \<subseteq> Pow UNIV" by simp
516 moreover have "finite (Pow (UNIV :: ('a * 'b) set))"
517 by (simp only: finite_Pow_iff finite)
518 ultimately show "finite (range ?graph)"
519 by (rule finite_subset)
520 show "inj ?graph" by (rule inj_graph)
524 instance sum :: (finite, finite) finite proof
525 qed (simp only: UNIV_Plus_UNIV [symmetric] finite_Plus finite)
528 subsection {* A basic fold functional for finite sets *}
530 text {* The intended behaviour is
531 @{text "fold f z {x\<^isub>1, ..., x\<^isub>n} = f x\<^isub>1 (\<dots> (f x\<^isub>n z)\<dots>)"}
532 if @{text f} is ``left-commutative'':
535 locale fun_left_comm =
536 fixes f :: "'a \<Rightarrow> 'b \<Rightarrow> 'b"
537 assumes commute_comp: "f y \<circ> f x = f x \<circ> f y"
540 lemma fun_left_comm: "f x (f y z) = f y (f x z)"
541 using commute_comp by (simp add: fun_eq_iff)
545 inductive fold_graph :: "('a \<Rightarrow> 'b \<Rightarrow> 'b) \<Rightarrow> 'b \<Rightarrow> 'a set \<Rightarrow> 'b \<Rightarrow> bool"
546 for f :: "'a \<Rightarrow> 'b \<Rightarrow> 'b" and z :: 'b where
547 emptyI [intro]: "fold_graph f z {} z" |
548 insertI [intro]: "x \<notin> A \<Longrightarrow> fold_graph f z A y
549 \<Longrightarrow> fold_graph f z (insert x A) (f x y)"
551 inductive_cases empty_fold_graphE [elim!]: "fold_graph f z {} x"
553 definition fold :: "('a \<Rightarrow> 'b \<Rightarrow> 'b) \<Rightarrow> 'b \<Rightarrow> 'a set \<Rightarrow> 'b" where
554 "fold f z A = (THE y. fold_graph f z A y)"
556 text{*A tempting alternative for the definiens is
557 @{term "if finite A then THE y. fold_graph f z A y else e"}.
558 It allows the removal of finiteness assumptions from the theorems
559 @{text fold_comm}, @{text fold_reindex} and @{text fold_distrib}.
560 The proofs become ugly. It is not worth the effort. (???) *}
562 lemma finite_imp_fold_graph: "finite A \<Longrightarrow> \<exists>x. fold_graph f z A x"
563 by (induct rule: finite_induct) auto
566 subsubsection{*From @{const fold_graph} to @{term fold}*}
568 context fun_left_comm
571 lemma fold_graph_insertE_aux:
572 "fold_graph f z A y \<Longrightarrow> a \<in> A \<Longrightarrow> \<exists>y'. y = f a y' \<and> fold_graph f z (A - {a}) y'"
573 proof (induct set: fold_graph)
574 case (insertI x A y) show ?case
575 proof (cases "x = a")
576 assume "x = a" with insertI show ?case by auto
578 assume "x \<noteq> a"
579 then obtain y' where y: "y = f a y'" and y': "fold_graph f z (A - {a}) y'"
580 using insertI by auto
581 have 1: "f x y = f a (f x y')"
582 unfolding y by (rule fun_left_comm)
583 have 2: "fold_graph f z (insert x A - {a}) (f x y')"
584 using y' and `x \<noteq> a` and `x \<notin> A`
585 by (simp add: insert_Diff_if fold_graph.insertI)
586 from 1 2 show ?case by fast
590 lemma fold_graph_insertE:
591 assumes "fold_graph f z (insert x A) v" and "x \<notin> A"
592 obtains y where "v = f x y" and "fold_graph f z A y"
593 using assms by (auto dest: fold_graph_insertE_aux [OF _ insertI1])
595 lemma fold_graph_determ:
596 "fold_graph f z A x \<Longrightarrow> fold_graph f z A y \<Longrightarrow> y = x"
597 proof (induct arbitrary: y set: fold_graph)
598 case (insertI x A y v)
599 from `fold_graph f z (insert x A) v` and `x \<notin> A`
600 obtain y' where "v = f x y'" and "fold_graph f z A y'"
601 by (rule fold_graph_insertE)
602 from `fold_graph f z A y'` have "y' = y" by (rule insertI)
603 with `v = f x y'` show "v = f x y" by simp
607 "fold_graph f z A y \<Longrightarrow> fold f z A = y"
608 by (unfold fold_def) (blast intro: fold_graph_determ)
610 lemma fold_graph_fold:
612 shows "fold_graph f z A (fold f z A)"
614 from assms have "\<exists>x. fold_graph f z A x" by (rule finite_imp_fold_graph)
615 moreover note fold_graph_determ
616 ultimately have "\<exists>!x. fold_graph f z A x" by (rule ex_ex1I)
617 then have "fold_graph f z A (The (fold_graph f z A))" by (rule theI')
618 then show ?thesis by (unfold fold_def)
621 text{* The base case for @{text fold}: *}
623 lemma (in -) fold_empty [simp]: "fold f z {} = z"
624 by (unfold fold_def) blast
626 text{* The various recursion equations for @{const fold}: *}
628 lemma fold_insert [simp]:
629 "finite A ==> x \<notin> A ==> fold f z (insert x A) = f x (fold f z A)"
630 apply (rule fold_equality)
631 apply (erule fold_graph.insertI)
632 apply (erule fold_graph_fold)
636 "finite A \<Longrightarrow> f x (fold f z A) = fold f (f x z) A"
637 proof (induct rule: finite_induct)
638 case empty then show ?case by simp
640 case (insert y A) then show ?case
641 by (simp add: fun_left_comm[of x])
645 "finite A \<Longrightarrow> x \<notin> A \<Longrightarrow> fold f z (insert x A) = fold f (f x z) A"
646 by (simp add: fold_fun_comm)
649 assumes "finite A" and "x \<in> A"
650 shows "fold f z A = f x (fold f z (A - {x}))"
652 have A: "A = insert x (A - {x})" using `x \<in> A` by blast
653 then have "fold f z A = fold f z (insert x (A - {x}))" by simp
654 also have "\<dots> = f x (fold f z (A - {x}))"
655 by (rule fold_insert) (simp add: `finite A`)+
656 finally show ?thesis .
659 lemma fold_insert_remove:
661 shows "fold f z (insert x A) = f x (fold f z (A - {x}))"
663 from `finite A` have "finite (insert x A)" by auto
664 moreover have "x \<in> insert x A" by auto
665 ultimately have "fold f z (insert x A) = f x (fold f z (insert x A - {x}))"
667 then show ?thesis by simp
672 text{* A simplified version for idempotent functions: *}
674 locale fun_left_comm_idem = fun_left_comm +
675 assumes fun_left_idem: "f x (f x z) = f x z"
678 text{* The nice version: *}
679 lemma fun_comp_idem : "f x o f x = f x"
680 by (simp add: fun_left_idem fun_eq_iff)
682 lemma fold_insert_idem:
683 assumes fin: "finite A"
684 shows "fold f z (insert x A) = f x (fold f z A)"
687 then obtain B where "A = insert x B" and "x \<notin> B" by (rule set_insert)
688 then show ?thesis using assms by (simp add:fun_left_idem)
690 assume "x \<notin> A" then show ?thesis using assms by simp
693 declare fold_insert[simp del] fold_insert_idem[simp]
695 lemma fold_insert_idem2:
696 "finite A \<Longrightarrow> fold f z (insert x A) = fold f (f x z) A"
697 by(simp add:fold_fun_comm)
702 subsubsection {* Expressing set operations via @{const fold} *}
704 lemma (in fun_left_comm) fun_left_comm_apply:
705 "fun_left_comm (\<lambda>x. f (g x))"
707 qed (simp_all add: commute_comp)
709 lemma (in fun_left_comm_idem) fun_left_comm_idem_apply:
710 "fun_left_comm_idem (\<lambda>x. f (g x))"
711 by (rule fun_left_comm_idem.intro, rule fun_left_comm_apply, unfold_locales)
712 (simp_all add: fun_left_idem)
714 lemma fun_left_comm_idem_insert:
715 "fun_left_comm_idem insert"
719 lemma fun_left_comm_idem_remove:
720 "fun_left_comm_idem (\<lambda>x A. A - {x})"
724 lemma (in semilattice_inf) fun_left_comm_idem_inf:
725 "fun_left_comm_idem inf"
727 qed (auto simp add: inf_left_commute)
729 lemma (in semilattice_sup) fun_left_comm_idem_sup:
730 "fun_left_comm_idem sup"
732 qed (auto simp add: sup_left_commute)
734 lemma union_fold_insert:
736 shows "A \<union> B = fold insert B A"
738 interpret fun_left_comm_idem insert by (fact fun_left_comm_idem_insert)
739 from `finite A` show ?thesis by (induct A arbitrary: B) simp_all
742 lemma minus_fold_remove:
744 shows "B - A = fold (\<lambda>x A. A - {x}) B A"
746 interpret fun_left_comm_idem "\<lambda>x A. A - {x}" by (fact fun_left_comm_idem_remove)
747 from `finite A` show ?thesis by (induct A arbitrary: B) auto
750 context complete_lattice
753 lemma inf_Inf_fold_inf:
755 shows "inf B (Inf A) = fold inf B A"
757 interpret fun_left_comm_idem inf by (fact fun_left_comm_idem_inf)
758 from `finite A` show ?thesis by (induct A arbitrary: B)
759 (simp_all add: Inf_insert inf_commute fold_fun_comm)
762 lemma sup_Sup_fold_sup:
764 shows "sup B (Sup A) = fold sup B A"
766 interpret fun_left_comm_idem sup by (fact fun_left_comm_idem_sup)
767 from `finite A` show ?thesis by (induct A arbitrary: B)
768 (simp_all add: Sup_insert sup_commute fold_fun_comm)
773 shows "Inf A = fold inf top A"
774 using assms inf_Inf_fold_inf [of A top] by (simp add: inf_absorb2)
778 shows "Sup A = fold sup bot A"
779 using assms sup_Sup_fold_sup [of A bot] by (simp add: sup_absorb2)
781 lemma inf_INFI_fold_inf:
783 shows "inf B (INFI A f) = fold (\<lambda>A. inf (f A)) B A" (is "?inf = ?fold")
785 interpret fun_left_comm_idem inf by (fact fun_left_comm_idem_inf)
786 interpret fun_left_comm_idem "\<lambda>A. inf (f A)" by (fact fun_left_comm_idem_apply)
787 from `finite A` show "?fold = ?inf"
788 by (induct A arbitrary: B)
789 (simp_all add: INFI_def Inf_insert inf_left_commute)
792 lemma sup_SUPR_fold_sup:
794 shows "sup B (SUPR A f) = fold (\<lambda>A. sup (f A)) B A" (is "?sup = ?fold")
796 interpret fun_left_comm_idem sup by (fact fun_left_comm_idem_sup)
797 interpret fun_left_comm_idem "\<lambda>A. sup (f A)" by (fact fun_left_comm_idem_apply)
798 from `finite A` show "?fold = ?sup"
799 by (induct A arbitrary: B)
800 (simp_all add: SUPR_def Sup_insert sup_left_commute)
805 shows "INFI A f = fold (\<lambda>A. inf (f A)) top A"
806 using assms inf_INFI_fold_inf [of A top] by simp
810 shows "SUPR A f = fold (\<lambda>A. sup (f A)) bot A"
811 using assms sup_SUPR_fold_sup [of A bot] by simp
816 subsection {* The derived combinator @{text fold_image} *}
818 definition fold_image :: "('b \<Rightarrow> 'b \<Rightarrow> 'b) \<Rightarrow> ('a \<Rightarrow> 'b) \<Rightarrow> 'b \<Rightarrow> 'a set \<Rightarrow> 'b"
819 where "fold_image f g = fold (%x y. f (g x) y)"
821 lemma fold_image_empty[simp]: "fold_image f g z {} = z"
822 by(simp add:fold_image_def)
824 context ab_semigroup_mult
827 lemma fold_image_insert[simp]:
828 assumes "finite A" and "a \<notin> A"
829 shows "fold_image times g z (insert a A) = g a * (fold_image times g z A)"
831 interpret I: fun_left_comm "%x y. (g x) * y" proof
832 qed (simp add: fun_eq_iff mult_ac)
833 show ?thesis using assms by (simp add: fold_image_def)
838 "finite A ==> (!!z. x * (fold times g z A) = fold times g (x * z) A)"
839 apply (induct set: finite)
841 apply (simp add: mult_left_commute [of x])
844 lemma fold_nest_Un_Int:
845 "finite A ==> finite B
846 ==> fold times g (fold times g z B) A = fold times g (fold times g z (A Int B)) (A Un B)"
847 apply (induct set: finite)
849 apply (simp add: fold_commute Int_insert_left insert_absorb)
852 lemma fold_nest_Un_disjoint:
853 "finite A ==> finite B ==> A Int B = {}
854 ==> fold times g z (A Un B) = fold times g (fold times g z B) A"
855 by (simp add: fold_nest_Un_Int)
858 lemma fold_image_reindex:
859 assumes fin: "finite A"
860 shows "inj_on h A \<Longrightarrow> fold_image times g z (h`A) = fold_image times (g\<circ>h) z A"
861 using fin by induct auto
865 Fusion theorem, as described in Graham Hutton's paper,
866 A Tutorial on the Universality and Expressiveness of Fold,
867 JFP 9:4 (355-372), 1999.
871 assumes "ab_semigroup_mult g"
872 assumes fin: "finite A"
873 and hyp: "\<And>x y. h (g x y) = times x (h y)"
874 shows "h (fold g j w A) = fold times j (h w) A"
876 class_interpret ab_semigroup_mult [g] by fact
877 show ?thesis using fin hyp by (induct set: finite) simp_all
881 lemma fold_image_cong:
882 "finite A \<Longrightarrow>
883 (!!x. x:A ==> g x = h x) ==> fold_image times g z A = fold_image times h z A"
884 apply (subgoal_tac "ALL C. C <= A --> (ALL x:C. g x = h x) --> fold_image times g z C = fold_image times h z C")
886 apply (erule finite_induct, simp)
887 apply (simp add: subset_insert_iff, clarify)
888 apply (subgoal_tac "finite C")
889 prefer 2 apply (blast dest: finite_subset [COMP swap_prems_rl])
890 apply (subgoal_tac "C = insert x (C - {x})")
894 apply (erule (1) notE impE)
895 apply (simp add: Ball_def del: insert_Diff_single)
900 context comm_monoid_mult
904 "finite S \<Longrightarrow> (\<forall>x\<in>S. f x = 1) \<Longrightarrow> fold_image op * f 1 S = 1"
905 apply (induct rule: finite_induct)
908 lemma fold_image_Un_Int:
909 "finite A ==> finite B ==>
910 fold_image times g 1 A * fold_image times g 1 B =
911 fold_image times g 1 (A Un B) * fold_image times g 1 (A Int B)"
912 apply (induct rule: finite_induct)
913 by (induct set: finite)
914 (auto simp add: mult_ac insert_absorb Int_insert_left)
916 lemma fold_image_Un_one:
917 assumes fS: "finite S" and fT: "finite T"
918 and I0: "\<forall>x \<in> S\<inter>T. f x = 1"
919 shows "fold_image (op *) f 1 (S \<union> T) = fold_image (op *) f 1 S * fold_image (op *) f 1 T"
921 have "fold_image op * f 1 (S \<inter> T) = 1"
922 apply (rule fold_image_1)
923 using fS fT I0 by auto
924 with fold_image_Un_Int[OF fS fT] show ?thesis by simp
927 corollary fold_Un_disjoint:
928 "finite A ==> finite B ==> A Int B = {} ==>
929 fold_image times g 1 (A Un B) =
930 fold_image times g 1 A * fold_image times g 1 B"
931 by (simp add: fold_image_Un_Int)
933 lemma fold_image_UN_disjoint:
934 "\<lbrakk> finite I; ALL i:I. finite (A i);
935 ALL i:I. ALL j:I. i \<noteq> j --> A i Int A j = {} \<rbrakk>
936 \<Longrightarrow> fold_image times g 1 (UNION I A) =
937 fold_image times (%i. fold_image times g 1 (A i)) 1 I"
938 apply (induct rule: finite_induct)
941 apply (subgoal_tac "ALL i:F. x \<noteq> i")
943 apply (subgoal_tac "A x Int UNION F A = {}")
945 apply (simp add: fold_Un_disjoint)
948 lemma fold_image_Sigma: "finite A ==> ALL x:A. finite (B x) ==>
949 fold_image times (%x. fold_image times (g x) 1 (B x)) 1 A =
950 fold_image times (split g) 1 (SIGMA x:A. B x)"
951 apply (subst Sigma_def)
952 apply (subst fold_image_UN_disjoint, assumption, simp)
954 apply (erule fold_image_cong)
955 apply (subst fold_image_UN_disjoint, simp, simp)
960 lemma fold_image_distrib: "finite A \<Longrightarrow>
961 fold_image times (%x. g x * h x) 1 A =
962 fold_image times g 1 A * fold_image times h 1 A"
963 by (erule finite_induct) (simp_all add: mult_ac)
965 lemma fold_image_related:
967 and Rop: "\<forall>x1 y1 x2 y2. R x1 x2 \<and> R y1 y2 \<longrightarrow> R (x1 * y1) (x2 * y2)"
968 and fS: "finite S" and Rfg: "\<forall>x\<in>S. R (h x) (g x)"
969 shows "R (fold_image (op *) h e S) (fold_image (op *) g e S)"
970 using fS by (rule finite_subset_induct) (insert assms, auto)
972 lemma fold_image_eq_general:
973 assumes fS: "finite S"
974 and h: "\<forall>y\<in>S'. \<exists>!x. x\<in> S \<and> h(x) = y"
975 and f12: "\<forall>x\<in>S. h x \<in> S' \<and> f2(h x) = f1 x"
976 shows "fold_image (op *) f1 e S = fold_image (op *) f2 e S'"
978 from h f12 have hS: "h ` S = S'" by auto
979 {fix x y assume H: "x \<in> S" "y \<in> S" "h x = h y"
980 from f12 h H have "x = y" by auto }
981 hence hinj: "inj_on h S" unfolding inj_on_def Ex1_def by blast
982 from f12 have th: "\<And>x. x \<in> S \<Longrightarrow> (f2 \<circ> h) x = f1 x" by auto
983 from hS have "fold_image (op *) f2 e S' = fold_image (op *) f2 e (h ` S)" by simp
984 also have "\<dots> = fold_image (op *) (f2 o h) e S"
985 using fold_image_reindex[OF fS hinj, of f2 e] .
986 also have "\<dots> = fold_image (op *) f1 e S " using th fold_image_cong[OF fS, of "f2 o h" f1 e]
988 finally show ?thesis ..
991 lemma fold_image_eq_general_inverses:
992 assumes fS: "finite S"
993 and kh: "\<And>y. y \<in> T \<Longrightarrow> k y \<in> S \<and> h (k y) = y"
994 and hk: "\<And>x. x \<in> S \<Longrightarrow> h x \<in> T \<and> k (h x) = x \<and> g (h x) = f x"
995 shows "fold_image (op *) f e S = fold_image (op *) g e T"
996 (* metis solves it, but not yet available here *)
997 apply (rule fold_image_eq_general[OF fS, of T h g f e])
1003 apply (drule hk) apply simp
1005 apply (erule conjunct1[OF conjunct2[OF hk]])
1014 subsection {* A fold functional for non-empty sets *}
1016 text{* Does not require start value. *}
1019 fold1Set :: "('a => 'a => 'a) => 'a set => 'a => bool"
1020 for f :: "'a => 'a => 'a"
1022 fold1Set_insertI [intro]:
1023 "\<lbrakk> fold_graph f a A x; a \<notin> A \<rbrakk> \<Longrightarrow> fold1Set f (insert a A) x"
1025 definition fold1 :: "('a => 'a => 'a) => 'a set => 'a" where
1026 "fold1 f A == THE x. fold1Set f A x"
1028 lemma fold1Set_nonempty:
1029 "fold1Set f A x \<Longrightarrow> A \<noteq> {}"
1030 by(erule fold1Set.cases, simp_all)
1032 inductive_cases empty_fold1SetE [elim!]: "fold1Set f {} x"
1034 inductive_cases insert_fold1SetE [elim!]: "fold1Set f (insert a X) x"
1037 lemma fold1Set_sing [iff]: "(fold1Set f {a} b) = (a = b)"
1038 by (blast elim: fold_graph.cases)
1040 lemma fold1_singleton [simp]: "fold1 f {a} = a"
1041 by (unfold fold1_def) blast
1043 lemma finite_nonempty_imp_fold1Set:
1044 "\<lbrakk> finite A; A \<noteq> {} \<rbrakk> \<Longrightarrow> EX x. fold1Set f A x"
1045 apply (induct A rule: finite_induct)
1046 apply (auto dest: finite_imp_fold_graph [of _ f])
1049 text{*First, some lemmas about @{const fold_graph}.*}
1051 context ab_semigroup_mult
1054 lemma fun_left_comm: "fun_left_comm (op *)" proof
1055 qed (simp add: fun_eq_iff mult_ac)
1057 lemma fold_graph_insert_swap:
1058 assumes fold: "fold_graph times (b::'a) A y" and "b \<notin> A"
1059 shows "fold_graph times z (insert b A) (z * y)"
1061 interpret fun_left_comm "op *::'a \<Rightarrow> 'a \<Rightarrow> 'a" by (rule fun_left_comm)
1062 from assms show ?thesis
1063 proof (induct rule: fold_graph.induct)
1064 case emptyI show ?case by (subst mult_commute [of z b], fast)
1066 case (insertI x A y)
1067 have "fold_graph times z (insert x (insert b A)) (x * (z * y))"
1068 using insertI by force --{*how does @{term id} get unfolded?*}
1069 thus ?case by (simp add: insert_commute mult_ac)
1073 lemma fold_graph_permute_diff:
1074 assumes fold: "fold_graph times b A x"
1075 shows "!!a. \<lbrakk>a \<in> A; b \<notin> A\<rbrakk> \<Longrightarrow> fold_graph times a (insert b (A-{a})) x"
1077 proof (induct rule: fold_graph.induct)
1078 case emptyI thus ?case by simp
1080 case (insertI x A y)
1081 have "a = x \<or> a \<in> A" using insertI by simp
1085 with insertI show ?thesis
1086 by (simp add: id_def [symmetric], blast intro: fold_graph_insert_swap)
1088 assume ainA: "a \<in> A"
1089 hence "fold_graph times a (insert x (insert b (A - {a}))) (x * y)"
1090 using insertI by force
1092 have "insert x (insert b (A - {a})) = insert b (insert x A - {a})"
1093 using ainA insertI by blast
1094 ultimately show ?thesis by simp
1098 lemma fold1_eq_fold:
1099 assumes "finite A" "a \<notin> A" shows "fold1 times (insert a A) = fold times a A"
1101 interpret fun_left_comm "op *::'a \<Rightarrow> 'a \<Rightarrow> 'a" by (rule fun_left_comm)
1102 from assms show ?thesis
1103 apply (simp add: fold1_def fold_def)
1104 apply (rule the_equality)
1105 apply (best intro: fold_graph_determ theI dest: finite_imp_fold_graph [of _ times])
1106 apply (rule sym, clarify)
1107 apply (case_tac "Aa=A")
1108 apply (best intro: fold_graph_determ)
1109 apply (subgoal_tac "fold_graph times a A x")
1110 apply (best intro: fold_graph_determ)
1111 apply (subgoal_tac "insert aa (Aa - {a}) = A")
1112 prefer 2 apply (blast elim: equalityE)
1113 apply (auto dest: fold_graph_permute_diff [where a=a])
1117 lemma nonempty_iff: "(A \<noteq> {}) = (\<exists>x B. A = insert x B & x \<notin> B)"
1120 apply (drule_tac x=x in spec)
1121 apply (drule_tac x="A-{x}" in spec, auto)
1125 assumes nonempty: "A \<noteq> {}" and A: "finite A" "x \<notin> A"
1126 shows "fold1 times (insert x A) = x * fold1 times A"
1128 interpret fun_left_comm "op *::'a \<Rightarrow> 'a \<Rightarrow> 'a" by (rule fun_left_comm)
1129 from nonempty obtain a A' where "A = insert a A' & a ~: A'"
1130 by (auto simp add: nonempty_iff)
1132 by (simp add: insert_commute [of x] fold1_eq_fold eq_commute)
1137 context ab_semigroup_idem_mult
1140 lemma fun_left_comm_idem: "fun_left_comm_idem (op *)" proof
1141 qed (simp add: fun_eq_iff mult_left_commute, rule mult_left_idem)
1143 lemma fold1_insert_idem [simp]:
1144 assumes nonempty: "A \<noteq> {}" and A: "finite A"
1145 shows "fold1 times (insert x A) = x * fold1 times A"
1147 interpret fun_left_comm_idem "op *::'a \<Rightarrow> 'a \<Rightarrow> 'a"
1148 by (rule fun_left_comm_idem)
1149 from nonempty obtain a A' where A': "A = insert a A' & a ~: A'"
1150 by (auto simp add: nonempty_iff)
1157 with A' a show ?thesis by simp
1159 assume "A' \<noteq> {}"
1160 with A A' a show ?thesis
1161 by (simp add: fold1_insert mult_assoc [symmetric])
1164 assume "a \<noteq> x"
1165 with A A' show ?thesis
1166 by (simp add: insert_commute fold1_eq_fold)
1170 lemma hom_fold1_commute:
1171 assumes hom: "!!x y. h (x * y) = h x * h y"
1172 and N: "finite N" "N \<noteq> {}" shows "h (fold1 times N) = fold1 times (h ` N)"
1173 using N proof (induct rule: finite_ne_induct)
1174 case singleton thus ?case by simp
1177 then have "h (fold1 times (insert n N)) = h (n * fold1 times N)" by simp
1178 also have "\<dots> = h n * h (fold1 times N)" by(rule hom)
1179 also have "h (fold1 times N) = fold1 times (h ` N)" by(rule insert)
1180 also have "times (h n) \<dots> = fold1 times (insert (h n) (h ` N))"
1181 using insert by(simp)
1182 also have "insert (h n) (h ` N) = h ` insert n N" by simp
1183 finally show ?case .
1186 lemma fold1_eq_fold_idem:
1188 shows "fold1 times (insert a A) = fold times a A"
1189 proof (cases "a \<in> A")
1191 with assms show ?thesis by (simp add: fold1_eq_fold)
1193 interpret fun_left_comm_idem times by (fact fun_left_comm_idem)
1194 case True then obtain b B
1195 where A: "A = insert a B" and "a \<notin> B" by (rule set_insert)
1196 with assms have "finite B" by auto
1197 then have "fold times a (insert a B) = fold times (a * a) B"
1198 using `a \<notin> B` by (rule fold_insert2)
1200 using `a \<notin> B` `finite B` by (simp add: fold1_eq_fold A)
1206 text{* Now the recursion rules for definitions: *}
1208 lemma fold1_singleton_def: "g = fold1 f \<Longrightarrow> g {a} = a"
1211 lemma (in ab_semigroup_mult) fold1_insert_def:
1212 "\<lbrakk> g = fold1 times; finite A; x \<notin> A; A \<noteq> {} \<rbrakk> \<Longrightarrow> g (insert x A) = x * g A"
1213 by (simp add:fold1_insert)
1215 lemma (in ab_semigroup_idem_mult) fold1_insert_idem_def:
1216 "\<lbrakk> g = fold1 times; finite A; A \<noteq> {} \<rbrakk> \<Longrightarrow> g (insert x A) = x * g A"
1219 subsubsection{* Determinacy for @{term fold1Set} *}
1221 (*Not actually used!!*)
1223 context ab_semigroup_mult
1226 lemma fold_graph_permute:
1227 "[|fold_graph times id b (insert a A) x; a \<notin> A; b \<notin> A|]
1228 ==> fold_graph times id a (insert b A) x"
1230 apply (auto dest: fold_graph_permute_diff)
1233 lemma fold1Set_determ:
1234 "fold1Set times A x ==> fold1Set times A y ==> y = x"
1235 proof (clarify elim!: fold1Set.cases)
1237 assume Ax: "fold_graph times id a A x"
1238 assume By: "fold_graph times id b B y"
1239 assume anotA: "a \<notin> A"
1240 assume bnotB: "b \<notin> B"
1241 assume eq: "insert a A = insert b B"
1245 hence "A=B" using anotA bnotB eq by (blast elim!: equalityE)
1246 thus ?thesis using Ax By same by (blast intro: fold_graph_determ)
1248 assume diff: "a\<noteq>b"
1250 have B: "B = insert a ?D" and A: "A = insert b ?D"
1251 and aB: "a \<in> B" and bA: "b \<in> A"
1252 using eq anotA bnotB diff by (blast elim!:equalityE)+
1254 have "fold_graph times id a (insert b ?D) y"
1255 by (auto intro: fold_graph_permute simp add: insert_absorb)
1257 have "fold_graph times id a (insert b ?D) x"
1258 by (simp add: A [symmetric] Ax)
1259 ultimately show ?thesis by (blast intro: fold_graph_determ)
1263 lemma fold1Set_equality: "fold1Set times A y ==> fold1 times A = y"
1264 by (unfold fold1_def) (blast intro: fold1Set_determ)
1270 empty_fold_graphE [rule del] fold_graph.intros [rule del]
1271 empty_fold1SetE [rule del] insert_fold1SetE [rule del]
1272 -- {* No more proofs involve these relations. *}
1274 subsubsection {* Lemmas about @{text fold1} *}
1276 context ab_semigroup_mult
1280 assumes A: "finite A" "A \<noteq> {}"
1281 shows "finite B \<Longrightarrow> B \<noteq> {} \<Longrightarrow> A Int B = {} \<Longrightarrow>
1282 fold1 times (A Un B) = fold1 times A * fold1 times B"
1283 using A by (induct rule: finite_ne_induct)
1284 (simp_all add: fold1_insert mult_assoc)
1287 assumes A: "finite (A)" "A \<noteq> {}" and elem: "\<And>x y. x * y \<in> {x,y}"
1288 shows "fold1 times A \<in> A"
1290 proof (induct rule:finite_ne_induct)
1291 case singleton thus ?case by simp
1293 case insert thus ?case using elem by (force simp add:fold1_insert)
1298 lemma (in ab_semigroup_idem_mult) fold1_Un2:
1299 assumes A: "finite A" "A \<noteq> {}"
1300 shows "finite B \<Longrightarrow> B \<noteq> {} \<Longrightarrow>
1301 fold1 times (A Un B) = fold1 times A * fold1 times B"
1303 proof(induct rule:finite_ne_induct)
1304 case singleton thus ?case by simp
1306 case insert thus ?case by (simp add: mult_assoc)
1310 subsection {* Locales as mini-packages for fold operations *}
1312 subsubsection {* The natural case *}
1315 fixes f :: "'a \<Rightarrow> 'b \<Rightarrow> 'b"
1316 fixes F :: "'a set \<Rightarrow> 'b \<Rightarrow> 'b"
1317 assumes commute_comp: "f y \<circ> f x = f x \<circ> f y"
1318 assumes eq_fold: "finite A \<Longrightarrow> F A s = fold f s A"
1323 by (simp add: eq_fold fun_eq_iff)
1325 lemma insert [simp]:
1326 assumes "finite A" and "x \<notin> A"
1327 shows "F (insert x A) = F A \<circ> f x"
1329 interpret fun_left_comm f proof
1330 qed (insert commute_comp, simp add: fun_eq_iff)
1331 from fold_insert2 assms
1332 have "\<And>s. fold f s (insert x A) = fold f (f x s) A" .
1333 with `finite A` show ?thesis by (simp add: eq_fold fun_eq_iff)
1337 assumes "finite A" and "x \<in> A"
1338 shows "F A = F (A - {x}) \<circ> f x"
1340 from `x \<in> A` obtain B where A: "A = insert x B" and "x \<notin> B"
1341 by (auto dest: mk_disjoint_insert)
1342 moreover from `finite A` this have "finite B" by simp
1343 ultimately show ?thesis by simp
1346 lemma insert_remove:
1348 shows "F (insert x A) = F (A - {x}) \<circ> f x"
1349 using assms by (cases "x \<in> A") (simp_all add: remove insert_absorb)
1351 lemma commute_left_comp:
1352 "f y \<circ> (f x \<circ> g) = f x \<circ> (f y \<circ> g)"
1353 by (simp add: o_assoc commute_comp)
1355 lemma commute_comp':
1357 shows "f x \<circ> F A = F A \<circ> f x"
1358 using assms by (induct A)
1359 (simp, simp del: o_apply add: o_assoc, simp del: o_apply add: o_assoc [symmetric] commute_comp)
1361 lemma commute_left_comp':
1363 shows "f x \<circ> (F A \<circ> g) = F A \<circ> (f x \<circ> g)"
1364 using assms by (simp add: o_assoc commute_comp')
1366 lemma commute_comp'':
1367 assumes "finite A" and "finite B"
1368 shows "F B \<circ> F A = F A \<circ> F B"
1369 using assms by (induct A)
1370 (simp_all add: o_assoc, simp add: o_assoc [symmetric] commute_comp')
1372 lemma commute_left_comp'':
1373 assumes "finite A" and "finite B"
1374 shows "F B \<circ> (F A \<circ> g) = F A \<circ> (F B \<circ> g)"
1375 using assms by (simp add: o_assoc commute_comp'')
1377 lemmas commute_comps = o_assoc [symmetric] commute_comp commute_left_comp
1378 commute_comp' commute_left_comp' commute_comp'' commute_left_comp''
1381 assumes "finite A" and "finite B"
1382 shows "F (A \<union> B) \<circ> F (A \<inter> B) = F A \<circ> F B"
1383 using assms by (induct A)
1384 (simp_all del: o_apply add: insert_absorb Int_insert_left commute_comps,
1388 assumes "finite A" and "finite B"
1389 and "A \<inter> B = {}"
1390 shows "F (A \<union> B) = F A \<circ> F B"
1392 from union_inter `finite A` `finite B` have "F (A \<union> B) \<circ> F (A \<inter> B) = F A \<circ> F B" .
1393 with `A \<inter> B = {}` show ?thesis by simp
1399 subsubsection {* The natural case with idempotency *}
1401 locale folding_idem = folding +
1402 assumes idem_comp: "f x \<circ> f x = f x"
1405 lemma idem_left_comp:
1406 "f x \<circ> (f x \<circ> g) = f x \<circ> g"
1407 by (simp add: o_assoc idem_comp)
1410 assumes "finite A" and "x \<in> A"
1411 shows "F A \<circ> f x = F A"
1412 using assms by (induct A)
1413 (auto simp add: commute_comps idem_comp, simp add: commute_left_comp' [symmetric] commute_comp')
1415 lemma subset_comp_idem:
1416 assumes "finite A" and "B \<subseteq> A"
1417 shows "F A \<circ> F B = F A"
1419 from assms have "finite B" by (blast dest: finite_subset)
1420 then show ?thesis using `B \<subseteq> A` by (induct B)
1421 (simp_all add: o_assoc in_comp_idem `finite A`)
1424 declare insert [simp del]
1426 lemma insert_idem [simp]:
1428 shows "F (insert x A) = F A \<circ> f x"
1429 using assms by (cases "x \<in> A") (simp_all add: insert in_comp_idem insert_absorb)
1432 assumes "finite A" and "finite B"
1433 shows "F (A \<union> B) = F A \<circ> F B"
1435 from assms have "finite (A \<union> B)" and "A \<inter> B \<subseteq> A \<union> B" by auto
1436 then have "F (A \<union> B) \<circ> F (A \<inter> B) = F (A \<union> B)" by (rule subset_comp_idem)
1437 with assms show ?thesis by (simp add: union_inter)
1443 subsubsection {* The image case with fixed function *}
1445 no_notation times (infixl "*" 70)
1446 no_notation Groups.one ("1")
1448 locale folding_image_simple = comm_monoid +
1449 fixes g :: "('b \<Rightarrow> 'a)"
1450 fixes F :: "'b set \<Rightarrow> 'a"
1451 assumes eq_fold_g: "finite A \<Longrightarrow> F A = fold_image f g 1 A"
1456 by (simp add: eq_fold_g)
1458 lemma insert [simp]:
1459 assumes "finite A" and "x \<notin> A"
1460 shows "F (insert x A) = g x * F A"
1462 interpret fun_left_comm "%x y. (g x) * y" proof
1463 qed (simp add: ac_simps fun_eq_iff)
1464 with assms have "fold_image (op *) g 1 (insert x A) = g x * fold_image (op *) g 1 A"
1465 by (simp add: fold_image_def)
1466 with `finite A` show ?thesis by (simp add: eq_fold_g)
1470 assumes "finite A" and "x \<in> A"
1471 shows "F A = g x * F (A - {x})"
1473 from `x \<in> A` obtain B where A: "A = insert x B" and "x \<notin> B"
1474 by (auto dest: mk_disjoint_insert)
1475 moreover from `finite A` this have "finite B" by simp
1476 ultimately show ?thesis by simp
1479 lemma insert_remove:
1481 shows "F (insert x A) = g x * F (A - {x})"
1482 using assms by (cases "x \<in> A") (simp_all add: remove insert_absorb)
1485 assumes "finite A" and "\<forall>x\<in>A. g x = 1"
1487 using assms by (induct A) simp_all
1490 assumes "finite A" and "finite B"
1491 shows "F (A \<union> B) * F (A \<inter> B) = F A * F B"
1492 using assms proof (induct A)
1493 case empty then show ?case by simp
1495 case (insert x A) then show ?case
1496 by (auto simp add: insert_absorb Int_insert_left commute [of _ "g x"] assoc left_commute)
1499 corollary union_inter_neutral:
1500 assumes "finite A" and "finite B"
1501 and I0: "\<forall>x \<in> A\<inter>B. g x = 1"
1502 shows "F (A \<union> B) = F A * F B"
1503 using assms by (simp add: union_inter [symmetric] neutral)
1505 corollary union_disjoint:
1506 assumes "finite A" and "finite B"
1507 assumes "A \<inter> B = {}"
1508 shows "F (A \<union> B) = F A * F B"
1509 using assms by (simp add: union_inter_neutral)
1514 subsubsection {* The image case with flexible function *}
1516 locale folding_image = comm_monoid +
1517 fixes F :: "('b \<Rightarrow> 'a) \<Rightarrow> 'b set \<Rightarrow> 'a"
1518 assumes eq_fold: "\<And>g. finite A \<Longrightarrow> F g A = fold_image f g 1 A"
1520 sublocale folding_image < folding_image_simple "op *" 1 g "F g" proof
1523 context folding_image
1526 lemma reindex: (* FIXME polymorhism *)
1527 assumes "finite A" and "inj_on h A"
1528 shows "F g (h ` A) = F (g \<circ> h) A"
1529 using assms by (induct A) auto
1532 assumes "finite A" and "\<And>x. x \<in> A \<Longrightarrow> g x = h x"
1533 shows "F g A = F h A"
1535 from assms have "ALL C. C <= A --> (ALL x:C. g x = h x) --> F g C = F h C"
1536 apply - apply (erule finite_induct) apply simp
1537 apply (simp add: subset_insert_iff, clarify)
1538 apply (subgoal_tac "finite C")
1539 prefer 2 apply (blast dest: finite_subset [COMP swap_prems_rl])
1540 apply (subgoal_tac "C = insert x (C - {x})")
1541 prefer 2 apply blast
1542 apply (erule ssubst)
1544 apply (erule (1) notE impE)
1545 apply (simp add: Ball_def del: insert_Diff_single)
1547 with assms show ?thesis by simp
1550 lemma UNION_disjoint:
1551 assumes "finite I" and "\<forall>i\<in>I. finite (A i)"
1552 and "\<forall>i\<in>I. \<forall>j\<in>I. i \<noteq> j \<longrightarrow> A i \<inter> A j = {}"
1553 shows "F g (UNION I A) = F (F g \<circ> A) I"
1554 apply (insert assms)
1555 apply (induct rule: finite_induct)
1558 apply (subgoal_tac "\<forall>i\<in>Fa. x \<noteq> i")
1559 prefer 2 apply blast
1560 apply (subgoal_tac "A x Int UNION Fa A = {}")
1561 prefer 2 apply blast
1562 apply (simp add: union_disjoint)
1567 shows "F (\<lambda>x. g x * h x) A = F g A * F h A"
1568 using assms by (rule finite_induct) (simp_all add: assoc commute left_commute)
1572 and Rop: "\<forall>x1 y1 x2 y2. R x1 x2 \<and> R y1 y2 \<longrightarrow> R (x1 * y1) (x2 * y2)"
1573 and fS: "finite S" and Rfg: "\<forall>x\<in>S. R (h x) (g x)"
1574 shows "R (F h S) (F g S)"
1575 using fS by (rule finite_subset_induct) (insert assms, auto)
1578 assumes fS: "finite S"
1579 and h: "\<forall>y\<in>S'. \<exists>!x. x \<in> S \<and> h x = y"
1580 and f12: "\<forall>x\<in>S. h x \<in> S' \<and> f2 (h x) = f1 x"
1581 shows "F f1 S = F f2 S'"
1583 from h f12 have hS: "h ` S = S'" by blast
1584 {fix x y assume H: "x \<in> S" "y \<in> S" "h x = h y"
1585 from f12 h H have "x = y" by auto }
1586 hence hinj: "inj_on h S" unfolding inj_on_def Ex1_def by blast
1587 from f12 have th: "\<And>x. x \<in> S \<Longrightarrow> (f2 \<circ> h) x = f1 x" by auto
1588 from hS have "F f2 S' = F f2 (h ` S)" by simp
1589 also have "\<dots> = F (f2 o h) S" using reindex [OF fS hinj, of f2] .
1590 also have "\<dots> = F f1 S " using th cong [OF fS, of "f2 o h" f1]
1592 finally show ?thesis ..
1595 lemma eq_general_inverses:
1596 assumes fS: "finite S"
1597 and kh: "\<And>y. y \<in> T \<Longrightarrow> k y \<in> S \<and> h (k y) = y"
1598 and hk: "\<And>x. x \<in> S \<Longrightarrow> h x \<in> T \<and> k (h x) = x \<and> g (h x) = j x"
1599 shows "F j S = F g T"
1600 (* metis solves it, but not yet available here *)
1601 apply (rule eq_general [OF fS, of T h g j])
1607 apply (drule hk) apply simp
1609 apply (erule conjunct1[OF conjunct2[OF hk]])
1618 subsubsection {* The image case with fixed function and idempotency *}
1620 locale folding_image_simple_idem = folding_image_simple +
1621 assumes idem: "x * x = x"
1623 sublocale folding_image_simple_idem < semilattice proof
1626 context folding_image_simple_idem
1630 assumes "finite A" and "x \<in> A"
1631 shows "g x * F A = F A"
1632 using assms by (induct A) (auto simp add: left_commute)
1635 assumes "finite A" and "B \<subseteq> A"
1636 shows "F B * F A = F A"
1638 from assms have "finite B" by (blast dest: finite_subset)
1639 then show ?thesis using `B \<subseteq> A` by (induct B)
1640 (auto simp add: assoc in_idem `finite A`)
1643 declare insert [simp del]
1645 lemma insert_idem [simp]:
1647 shows "F (insert x A) = g x * F A"
1648 using assms by (cases "x \<in> A") (simp_all add: insert in_idem insert_absorb)
1651 assumes "finite A" and "finite B"
1652 shows "F (A \<union> B) = F A * F B"
1654 from assms have "finite (A \<union> B)" and "A \<inter> B \<subseteq> A \<union> B" by auto
1655 then have "F (A \<inter> B) * F (A \<union> B) = F (A \<union> B)" by (rule subset_idem)
1656 with assms show ?thesis by (simp add: union_inter [of A B, symmetric] commute)
1662 subsubsection {* The image case with flexible function and idempotency *}
1664 locale folding_image_idem = folding_image +
1665 assumes idem: "x * x = x"
1667 sublocale folding_image_idem < folding_image_simple_idem "op *" 1 g "F g" proof
1671 subsubsection {* The neutral-less case *}
1673 locale folding_one = abel_semigroup +
1674 fixes F :: "'a set \<Rightarrow> 'a"
1675 assumes eq_fold: "finite A \<Longrightarrow> F A = fold1 f A"
1678 lemma singleton [simp]:
1680 by (simp add: eq_fold)
1683 assumes "finite A" and "x \<notin> A"
1684 shows "F (insert x A) = fold (op *) x A"
1686 interpret ab_semigroup_mult "op *" proof qed (simp_all add: ac_simps)
1687 with assms show ?thesis by (simp add: eq_fold fold1_eq_fold)
1690 lemma insert [simp]:
1691 assumes "finite A" and "x \<notin> A" and "A \<noteq> {}"
1692 shows "F (insert x A) = x * F A"
1694 from `A \<noteq> {}` obtain b where "b \<in> A" by blast
1695 then obtain B where *: "A = insert b B" "b \<notin> B" by (blast dest: mk_disjoint_insert)
1696 with `finite A` have "finite B" by simp
1697 interpret fold: folding "op *" "\<lambda>a b. fold (op *) b a" proof
1698 qed (simp_all add: fun_eq_iff ac_simps)
1699 thm fold.commute_comp' [of B b, simplified fun_eq_iff, simplified]
1700 from `finite B` fold.commute_comp' [of B x]
1701 have "op * x \<circ> (\<lambda>b. fold op * b B) = (\<lambda>b. fold op * b B) \<circ> op * x" by simp
1702 then have A: "x * fold op * b B = fold op * (b * x) B" by (simp add: fun_eq_iff commute)
1703 from `finite B` * fold.insert [of B b]
1704 have "(\<lambda>x. fold op * x (insert b B)) = (\<lambda>x. fold op * x B) \<circ> op * b" by simp
1705 then have B: "fold op * x (insert b B) = fold op * (b * x) B" by (simp add: fun_eq_iff)
1706 from A B assms * show ?thesis by (simp add: eq_fold' del: fold.insert)
1710 assumes "finite A" and "x \<in> A"
1711 shows "F A = (if A - {x} = {} then x else x * F (A - {x}))"
1713 from assms obtain B where "A = insert x B" and "x \<notin> B" by (blast dest: mk_disjoint_insert)
1714 with assms show ?thesis by simp
1717 lemma insert_remove:
1719 shows "F (insert x A) = (if A - {x} = {} then x else x * F (A - {x}))"
1720 using assms by (cases "x \<in> A") (simp_all add: insert_absorb remove)
1722 lemma union_disjoint:
1723 assumes "finite A" "A \<noteq> {}" and "finite B" "B \<noteq> {}" and "A \<inter> B = {}"
1724 shows "F (A \<union> B) = F A * F B"
1725 using assms by (induct A rule: finite_ne_induct) (simp_all add: ac_simps)
1728 assumes "finite A" and "finite B" and "A \<inter> B \<noteq> {}"
1729 shows "F (A \<union> B) * F (A \<inter> B) = F A * F B"
1731 from assms have "A \<noteq> {}" and "B \<noteq> {}" by auto
1732 from `finite A` `A \<noteq> {}` `A \<inter> B \<noteq> {}` show ?thesis proof (induct A rule: finite_ne_induct)
1733 case (singleton x) then show ?case by (simp add: insert_absorb ac_simps)
1735 case (insert x A) show ?case proof (cases "x \<in> B")
1736 case True then have "B \<noteq> {}" by auto
1737 with insert True `finite B` show ?thesis by (cases "A \<inter> B = {}")
1738 (simp_all add: insert_absorb ac_simps union_disjoint)
1740 case False with insert have "F (A \<union> B) * F (A \<inter> B) = F A * F B" by simp
1741 moreover from False `finite B` insert have "finite (A \<union> B)" "x \<notin> A \<union> B" "A \<union> B \<noteq> {}"
1743 ultimately show ?thesis using False `finite A` `x \<notin> A` `A \<noteq> {}` by (simp add: assoc)
1749 assumes "finite A" "A \<noteq> {}" and elem: "\<And>x y. x * y \<in> {x, y}"
1751 using `finite A` `A \<noteq> {}` proof (induct rule: finite_ne_induct)
1752 case singleton then show ?case by simp
1754 case insert with elem show ?case by force
1760 subsubsection {* The neutral-less case with idempotency *}
1762 locale folding_one_idem = folding_one +
1763 assumes idem: "x * x = x"
1765 sublocale folding_one_idem < semilattice proof
1768 context folding_one_idem
1772 assumes "finite A" and "x \<in> A"
1773 shows "x * F A = F A"
1775 from assms have "A \<noteq> {}" by auto
1776 with `finite A` show ?thesis using `x \<in> A` by (induct A rule: finite_ne_induct) (auto simp add: ac_simps)
1780 assumes "finite A" "B \<noteq> {}" and "B \<subseteq> A"
1781 shows "F B * F A = F A"
1783 from assms have "finite B" by (blast dest: finite_subset)
1784 then show ?thesis using `B \<noteq> {}` `B \<subseteq> A` by (induct B rule: finite_ne_induct)
1785 (simp_all add: assoc in_idem `finite A`)
1788 lemma eq_fold_idem':
1790 shows "F (insert a A) = fold (op *) a A"
1792 interpret ab_semigroup_idem_mult "op *" proof qed (simp_all add: ac_simps)
1793 with assms show ?thesis by (simp add: eq_fold fold1_eq_fold_idem)
1796 lemma insert_idem [simp]:
1797 assumes "finite A" and "A \<noteq> {}"
1798 shows "F (insert x A) = x * F A"
1799 proof (cases "x \<in> A")
1800 case False from `finite A` `x \<notin> A` `A \<noteq> {}` show ?thesis by (rule insert)
1803 from `finite A` `A \<noteq> {}` show ?thesis by (simp add: in_idem insert_absorb True)
1807 assumes "finite A" "A \<noteq> {}" and "finite B" "B \<noteq> {}"
1808 shows "F (A \<union> B) = F A * F B"
1809 proof (cases "A \<inter> B = {}")
1810 case True with assms show ?thesis by (simp add: union_disjoint)
1813 from assms have "finite (A \<union> B)" and "A \<inter> B \<subseteq> A \<union> B" by auto
1814 with False have "F (A \<inter> B) * F (A \<union> B) = F (A \<union> B)" by (auto intro: subset_idem)
1815 with assms False show ?thesis by (simp add: union_inter [of A B, symmetric] commute)
1819 assumes hom: "\<And>x y. h (x * y) = h x * h y"
1820 and N: "finite N" "N \<noteq> {}" shows "h (F N) = F (h ` N)"
1821 using N proof (induct rule: finite_ne_induct)
1822 case singleton thus ?case by simp
1825 then have "h (F (insert n N)) = h (n * F N)" by simp
1826 also have "\<dots> = h n * h (F N)" by (rule hom)
1827 also have "h (F N) = F (h ` N)" by(rule insert)
1828 also have "h n * \<dots> = F (insert (h n) (h ` N))"
1829 using insert by(simp)
1830 also have "insert (h n) (h ` N) = h ` insert n N" by simp
1831 finally show ?case .
1836 notation times (infixl "*" 70)
1837 notation Groups.one ("1")
1840 subsection {* Finite cardinality *}
1842 text {* This definition, although traditional, is ugly to work with:
1843 @{text "card A == LEAST n. EX f. A = {f i | i. i < n}"}.
1844 But now that we have @{text fold_image} things are easy:
1847 definition card :: "'a set \<Rightarrow> nat" where
1848 "card A = (if finite A then fold_image (op +) (\<lambda>x. 1) 0 A else 0)"
1850 interpretation card: folding_image_simple "op +" 0 "\<lambda>x. 1" card proof
1851 qed (simp add: card_def)
1853 lemma card_infinite [simp]:
1854 "\<not> finite A \<Longrightarrow> card A = 0"
1855 by (simp add: card_def)
1859 by (fact card.empty)
1861 lemma card_insert_disjoint:
1862 "finite A ==> x \<notin> A ==> card (insert x A) = Suc (card A)"
1865 lemma card_insert_if:
1866 "finite A ==> card (insert x A) = (if x \<in> A then card A else Suc (card A))"
1867 by auto (simp add: card.insert_remove card.remove)
1869 lemma card_ge_0_finite:
1870 "card A > 0 \<Longrightarrow> finite A"
1871 by (rule ccontr) simp
1873 lemma card_0_eq [simp, no_atp]:
1874 "finite A \<Longrightarrow> card A = 0 \<longleftrightarrow> A = {}"
1875 by (auto dest: mk_disjoint_insert)
1877 lemma finite_UNIV_card_ge_0:
1878 "finite (UNIV :: 'a set) \<Longrightarrow> card (UNIV :: 'a set) > 0"
1879 by (rule ccontr) simp
1881 lemma card_eq_0_iff:
1882 "card A = 0 \<longleftrightarrow> A = {} \<or> \<not> finite A"
1885 lemma card_gt_0_iff:
1886 "0 < card A \<longleftrightarrow> A \<noteq> {} \<and> finite A"
1887 by (simp add: neq0_conv [symmetric] card_eq_0_iff)
1889 lemma card_Suc_Diff1: "finite A ==> x: A ==> Suc (card (A - {x})) = card A"
1890 apply(rule_tac t = A in insert_Diff [THEN subst], assumption)
1891 apply(simp del:insert_Diff_single)
1894 lemma card_Diff_singleton:
1895 "finite A ==> x: A ==> card (A - {x}) = card A - 1"
1896 by (simp add: card_Suc_Diff1 [symmetric])
1898 lemma card_Diff_singleton_if:
1899 "finite A ==> card (A-{x}) = (if x : A then card A - 1 else card A)"
1900 by (simp add: card_Diff_singleton)
1902 lemma card_Diff_insert[simp]:
1903 assumes "finite A" and "a:A" and "a ~: B"
1904 shows "card(A - insert a B) = card(A - B) - 1"
1906 have "A - insert a B = (A - B) - {a}" using assms by blast
1907 then show ?thesis using assms by(simp add:card_Diff_singleton)
1910 lemma card_insert: "finite A ==> card (insert x A) = Suc (card (A - {x}))"
1911 by (simp add: card_insert_if card_Suc_Diff1 del:card_Diff_insert)
1913 lemma card_insert_le: "finite A ==> card A <= card (insert x A)"
1914 by (simp add: card_insert_if)
1916 lemma card_Collect_less_nat[simp]: "card{i::nat. i < n} = n"
1917 by (induct n) (simp_all add:less_Suc_eq Collect_disj_eq)
1919 lemma card_Collect_le_nat[simp]: "card{i::nat. i <= n} = Suc n"
1920 using card_Collect_less_nat[of "Suc n"] by(simp add: less_Suc_eq_le)
1923 assumes "finite B" and "A \<subseteq> B"
1924 shows "card A \<le> card B"
1926 from assms have "finite A" by (auto intro: finite_subset)
1927 then show ?thesis using assms proof (induct A arbitrary: B)
1928 case empty then show ?case by simp
1931 then have "x \<in> B" by simp
1932 from insert have "A \<subseteq> B - {x}" and "finite (B - {x})" by auto
1933 with insert.hyps have "card A \<le> card (B - {x})" by auto
1934 with `finite A` `x \<notin> A` `finite B` `x \<in> B` show ?case by simp (simp only: card.remove)
1938 lemma card_seteq: "finite B ==> (!!A. A <= B ==> card B <= card A ==> A = B)"
1939 apply (induct rule: finite_induct)
1942 apply (subgoal_tac "finite A & A - {x} <= F")
1943 prefer 2 apply (blast intro: finite_subset, atomize)
1944 apply (drule_tac x = "A - {x}" in spec)
1945 apply (simp add: card_Diff_singleton_if split add: split_if_asm)
1946 apply (case_tac "card A", auto)
1949 lemma psubset_card_mono: "finite B ==> A < B ==> card A < card B"
1950 apply (simp add: psubset_eq linorder_not_le [symmetric])
1951 apply (blast dest: card_seteq)
1954 lemma card_Un_Int: "finite A ==> finite B
1955 ==> card A + card B = card (A Un B) + card (A Int B)"
1956 by (fact card.union_inter [symmetric])
1958 lemma card_Un_disjoint: "finite A ==> finite B
1959 ==> A Int B = {} ==> card (A Un B) = card A + card B"
1960 by (fact card.union_disjoint)
1962 lemma card_Diff_subset:
1963 assumes "finite B" and "B \<subseteq> A"
1964 shows "card (A - B) = card A - card B"
1965 proof (cases "finite A")
1966 case False with assms show ?thesis by simp
1968 case True with assms show ?thesis by (induct B arbitrary: A) simp_all
1971 lemma card_Diff_subset_Int:
1972 assumes AB: "finite (A \<inter> B)" shows "card (A - B) = card A - card (A \<inter> B)"
1974 have "A - B = A - A \<inter> B" by auto
1976 by (simp add: card_Diff_subset AB)
1979 lemma diff_card_le_card_Diff:
1980 assumes "finite B" shows "card A - card B \<le> card(A - B)"
1982 have "card A - card B \<le> card A - card (A \<inter> B)"
1983 using card_mono[OF assms Int_lower2, of A] by arith
1984 also have "\<dots> = card(A-B)" using assms by(simp add: card_Diff_subset_Int)
1985 finally show ?thesis .
1988 lemma card_Diff1_less: "finite A ==> x: A ==> card (A - {x}) < card A"
1989 apply (rule Suc_less_SucD)
1990 apply (simp add: card_Suc_Diff1 del:card_Diff_insert)
1993 lemma card_Diff2_less:
1994 "finite A ==> x: A ==> y: A ==> card (A - {x} - {y}) < card A"
1995 apply (case_tac "x = y")
1996 apply (simp add: card_Diff1_less del:card_Diff_insert)
1997 apply (rule less_trans)
1998 prefer 2 apply (auto intro!: card_Diff1_less simp del:card_Diff_insert)
2001 lemma card_Diff1_le: "finite A ==> card (A - {x}) <= card A"
2002 apply (case_tac "x : A")
2003 apply (simp_all add: card_Diff1_less less_imp_le)
2006 lemma card_psubset: "finite B ==> A \<subseteq> B ==> card A < card B ==> A < B"
2007 by (erule psubsetI, blast)
2009 lemma insert_partition:
2010 "\<lbrakk> x \<notin> F; \<forall>c1 \<in> insert x F. \<forall>c2 \<in> insert x F. c1 \<noteq> c2 \<longrightarrow> c1 \<inter> c2 = {} \<rbrakk>
2011 \<Longrightarrow> x \<inter> \<Union> F = {}"
2014 lemma finite_psubset_induct[consumes 1, case_names psubset]:
2015 assumes fin: "finite A"
2016 and major: "\<And>A. finite A \<Longrightarrow> (\<And>B. B \<subset> A \<Longrightarrow> P B) \<Longrightarrow> P A"
2019 proof (induct A taking: card rule: measure_induct_rule)
2021 have fin: "finite A" by fact
2022 have ih: "\<And>B. \<lbrakk>card B < card A; finite B\<rbrakk> \<Longrightarrow> P B" by fact
2024 assume asm: "B \<subset> A"
2025 from asm have "card B < card A" using psubset_card_mono fin by blast
2027 from asm have "B \<subseteq> A" by auto
2028 then have "finite B" using fin finite_subset by blast
2030 have "P B" using ih by simp
2032 with fin show "P A" using major by blast
2035 text{* main cardinality theorem *}
2036 lemma card_partition [rule_format]:
2038 finite (\<Union> C) -->
2039 (\<forall>c\<in>C. card c = k) -->
2040 (\<forall>c1 \<in> C. \<forall>c2 \<in> C. c1 \<noteq> c2 --> c1 \<inter> c2 = {}) -->
2041 k * card(C) = card (\<Union> C)"
2042 apply (erule finite_induct, simp)
2043 apply (simp add: card_Un_disjoint insert_partition
2044 finite_subset [of _ "\<Union> (insert x F)"])
2047 lemma card_eq_UNIV_imp_eq_UNIV:
2048 assumes fin: "finite (UNIV :: 'a set)"
2049 and card: "card A = card (UNIV :: 'a set)"
2050 shows "A = (UNIV :: 'a set)"
2052 show "A \<subseteq> UNIV" by simp
2053 show "UNIV \<subseteq> A"
2058 assume "x \<notin> A"
2059 then have "A \<subset> UNIV" by auto
2060 with fin have "card A < card (UNIV :: 'a set)" by (fact psubset_card_mono)
2061 with card show False by simp
2066 text{*The form of a finite set of given cardinality*}
2069 assumes "card A = Suc k"
2070 shows "\<exists>b B. A = insert b B & b \<notin> B & card B = k & (k=0 \<longrightarrow> B={})"
2072 have fin: "finite A" using assms by (auto intro: ccontr)
2073 moreover have "card A \<noteq> 0" using assms by auto
2074 ultimately obtain b where b: "b \<in> A" by auto
2076 proof (intro exI conjI)
2077 show "A = insert b (A-{b})" using b by blast
2078 show "b \<notin> A - {b}" by blast
2079 show "card (A - {b}) = k" and "k = 0 \<longrightarrow> A - {b} = {}"
2080 using assms b fin by(fastsimp dest:mk_disjoint_insert)+
2086 (\<exists>b B. A = insert b B & b \<notin> B & card B = k & (k=0 \<longrightarrow> B={}))"
2088 apply(erule card_eq_SucD)
2090 apply(subst card_insert)
2091 apply(auto intro:ccontr)
2094 lemma finite_fun_UNIVD2:
2095 assumes fin: "finite (UNIV :: ('a \<Rightarrow> 'b) set)"
2096 shows "finite (UNIV :: 'b set)"
2098 from fin have "finite (range (\<lambda>f :: 'a \<Rightarrow> 'b. f arbitrary))"
2099 by(rule finite_imageI)
2100 moreover have "UNIV = range (\<lambda>f :: 'a \<Rightarrow> 'b. f arbitrary)"
2101 by(rule UNIV_eq_I) auto
2102 ultimately show "finite (UNIV :: 'b set)" by simp
2105 lemma card_UNIV_unit: "card (UNIV :: unit set) = 1"
2106 unfolding UNIV_unit by simp
2109 subsubsection {* Cardinality of image *}
2111 lemma card_image_le: "finite A ==> card (f ` A) <= card A"
2112 apply (induct rule: finite_induct)
2114 apply (simp add: le_SucI card_insert_if)
2118 assumes "inj_on f A"
2119 shows "card (f ` A) = card A"
2120 proof (cases "finite A")
2121 case True then show ?thesis using assms by (induct A) simp_all
2123 case False then have "\<not> finite (f ` A)" using assms by (auto dest: finite_imageD)
2124 with False show ?thesis by simp
2127 lemma bij_betw_same_card: "bij_betw f A B \<Longrightarrow> card A = card B"
2128 by(auto simp: card_image bij_betw_def)
2130 lemma endo_inj_surj: "finite A ==> f ` A \<subseteq> A ==> inj_on f A ==> f ` A = A"
2131 by (simp add: card_seteq card_image)
2133 lemma eq_card_imp_inj_on:
2134 "[| finite A; card(f ` A) = card A |] ==> inj_on f A"
2135 apply (induct rule:finite_induct)
2137 apply(frule card_image_le[where f = f])
2138 apply(simp add:card_insert_if split:if_splits)
2141 lemma inj_on_iff_eq_card:
2142 "finite A ==> inj_on f A = (card(f ` A) = card A)"
2143 by(blast intro: card_image eq_card_imp_inj_on)
2146 lemma card_inj_on_le:
2147 "[|inj_on f A; f ` A \<subseteq> B; finite B |] ==> card A \<le> card B"
2148 apply (subgoal_tac "finite A")
2149 apply (force intro: card_mono simp add: card_image [symmetric])
2150 apply (blast intro: finite_imageD dest: finite_subset)
2154 "[|inj_on f A; f ` A \<subseteq> B; inj_on g B; g ` B \<subseteq> A;
2155 finite A; finite B |] ==> card A = card B"
2156 by (auto intro: le_antisym card_inj_on_le)
2158 lemma bij_betw_finite:
2159 assumes "bij_betw f A B"
2160 shows "finite A \<longleftrightarrow> finite B"
2161 using assms unfolding bij_betw_def
2162 using finite_imageD[of f A] by auto
2165 subsubsection {* Pigeonhole Principles *}
2167 lemma pigeonhole: "card A > card(f ` A) \<Longrightarrow> ~ inj_on f A "
2168 by (auto dest: card_image less_irrefl_nat)
2170 lemma pigeonhole_infinite:
2171 assumes "~ finite A" and "finite(f`A)"
2172 shows "EX a0:A. ~finite{a:A. f a = f a0}"
2174 have "finite(f`A) \<Longrightarrow> ~ finite A \<Longrightarrow> EX a0:A. ~finite{a:A. f a = f a0}"
2175 proof(induct "f`A" arbitrary: A rule: finite_induct)
2176 case empty thus ?case by simp
2181 assume "finite{a:A. f a = b}"
2182 hence "~ finite(A - {a:A. f a = b})" using `\<not> finite A` by simp
2183 also have "A - {a:A. f a = b} = {a:A. f a \<noteq> b}" by blast
2184 finally have "~ finite({a:A. f a \<noteq> b})" .
2185 from insert(3)[OF _ this]
2186 show ?thesis using insert(2,4) by simp (blast intro: rev_finite_subset)
2188 assume 1: "~finite{a:A. f a = b}"
2189 hence "{a \<in> A. f a = b} \<noteq> {}" by force
2190 thus ?thesis using 1 by blast
2193 from this[OF assms(2,1)] show ?thesis .
2196 lemma pigeonhole_infinite_rel:
2197 assumes "~finite A" and "finite B" and "ALL a:A. EX b:B. R a b"
2198 shows "EX b:B. ~finite{a:A. R a b}"
2200 let ?F = "%a. {b:B. R a b}"
2201 from finite_Pow_iff[THEN iffD2, OF `finite B`]
2202 have "finite(?F ` A)" by(blast intro: rev_finite_subset)
2203 from pigeonhole_infinite[where f = ?F, OF assms(1) this]
2204 obtain a0 where "a0\<in>A" and 1: "\<not> finite {a\<in>A. ?F a = ?F a0}" ..
2205 obtain b0 where "b0 : B" and "R a0 b0" using `a0:A` assms(3) by blast
2206 { assume "finite{a:A. R a b0}"
2207 then have "finite {a\<in>A. ?F a = ?F a0}"
2208 using `b0 : B` `R a0 b0` by(blast intro: rev_finite_subset)
2210 with 1 `b0 : B` show ?thesis by blast
2214 subsubsection {* Cardinality of sums *}
2217 assumes "finite A" and "finite B"
2218 shows "card (A <+> B) = card A + card B"
2220 have "Inl`A \<inter> Inr`B = {}" by fast
2221 with assms show ?thesis
2223 by (simp add: card_Un_disjoint card_image)
2226 lemma card_Plus_conv_if:
2227 "card (A <+> B) = (if finite A \<and> finite B then card A + card B else 0)"
2228 by (auto simp add: card_Plus)
2231 subsubsection {* Cardinality of the Powerset *}
2233 lemma card_Pow: "finite A ==> card (Pow A) = Suc (Suc 0) ^ card A" (* FIXME numeral 2 (!?) *)
2234 apply (induct rule: finite_induct)
2235 apply (simp_all add: Pow_insert)
2236 apply (subst card_Un_disjoint, blast)
2237 apply (blast, blast)
2238 apply (subgoal_tac "inj_on (insert x) (Pow F)")
2239 apply (simp add: card_image Pow_insert)
2240 apply (unfold inj_on_def)
2241 apply (blast elim!: equalityE)
2244 text {* Relates to equivalence classes. Based on a theorem of F. Kamm\"uller. *}
2246 lemma dvd_partition:
2247 "finite (Union C) ==>
2248 ALL c : C. k dvd card c ==>
2249 (ALL c1: C. ALL c2: C. c1 \<noteq> c2 --> c1 Int c2 = {}) ==>
2250 k dvd card (Union C)"
2251 apply (frule finite_UnionD)
2252 apply (rotate_tac -1)
2253 apply (induct rule: finite_induct)
2256 apply (subst card_Un_disjoint)
2257 apply (auto simp add: disjoint_eq_subset_Compl)
2261 subsubsection {* Relating injectivity and surjectivity *}
2263 lemma finite_surj_inj: "finite A \<Longrightarrow> A \<subseteq> f ` A \<Longrightarrow> inj_on f A"
2264 apply(rule eq_card_imp_inj_on, assumption)
2265 apply(frule finite_imageI)
2266 apply(drule (1) card_seteq)
2267 apply(erule card_image_le)
2271 lemma finite_UNIV_surj_inj: fixes f :: "'a \<Rightarrow> 'a"
2272 shows "finite(UNIV:: 'a set) \<Longrightarrow> surj f \<Longrightarrow> inj f"
2273 by (blast intro: finite_surj_inj subset_UNIV)
2275 lemma finite_UNIV_inj_surj: fixes f :: "'a \<Rightarrow> 'a"
2276 shows "finite(UNIV:: 'a set) \<Longrightarrow> inj f \<Longrightarrow> surj f"
2277 by(fastsimp simp:surj_def dest!: endo_inj_surj)
2279 corollary infinite_UNIV_nat[iff]: "~finite(UNIV::nat set)"
2281 assume "finite(UNIV::nat set)"
2282 with finite_UNIV_inj_surj[of Suc]
2283 show False by simp (blast dest: Suc_neq_Zero surjD)
2286 (* Often leads to bogus ATP proofs because of reduced type information, hence no_atp *)
2287 lemma infinite_UNIV_char_0[no_atp]:
2288 "\<not> finite (UNIV::'a::semiring_char_0 set)"
2290 assume "finite (UNIV::'a set)"
2291 with subset_UNIV have "finite (range of_nat::'a set)"
2292 by (rule finite_subset)
2293 moreover have "inj (of_nat::nat \<Rightarrow> 'a)"
2294 by (simp add: inj_on_def)
2295 ultimately have "finite (UNIV::nat set)"
2296 by (rule finite_imageD)