2 Author: Tobias Nipkow, Cambridge University Computer Laboratory
3 Copyright 1994 University of Cambridge
6 header {* Notions about functions *}
9 imports Complete_Lattice
10 uses ("Tools/enriched_type.ML")
13 text{*As a simplification rule, it replaces all function equalities by
14 first-order equalities.*}
15 lemma fun_eq_iff: "f = g \<longleftrightarrow> (\<forall>x. f x = g x)"
17 apply (simp (no_asm_simp))
19 apply (simp (no_asm_simp))
23 "f x = u \<Longrightarrow> (\<And>x. P x \<Longrightarrow> g (f x) = x) \<Longrightarrow> P x \<Longrightarrow> x = g u"
27 subsection {* The Identity Function @{text id} *}
30 id :: "'a \<Rightarrow> 'a"
32 "id = (\<lambda>x. x)"
34 lemma id_apply [simp]: "id x = x"
37 lemma image_ident [simp]: "(%x. x) ` Y = Y"
40 lemma image_id [simp]: "id ` Y = Y"
43 lemma vimage_ident [simp]: "(%x. x) -` Y = Y"
46 lemma vimage_id [simp]: "id -` A = A"
50 subsection {* The Composition Operator @{text "f \<circ> g"} *}
53 comp :: "('b \<Rightarrow> 'c) \<Rightarrow> ('a \<Rightarrow> 'b) \<Rightarrow> 'a \<Rightarrow> 'c" (infixl "o" 55)
55 "f o g = (\<lambda>x. f (g x))"
58 comp (infixl "\<circ>" 55)
60 notation (HTML output)
61 comp (infixl "\<circ>" 55)
64 lemmas o_def = comp_def
66 lemma o_apply [simp]: "(f o g) x = f (g x)"
67 by (simp add: comp_def)
69 lemma o_assoc: "f o (g o h) = f o g o h"
70 by (simp add: comp_def)
72 lemma id_o [simp]: "id o g = g"
73 by (simp add: comp_def)
75 lemma o_id [simp]: "f o id = f"
76 by (simp add: comp_def)
79 "a o b = c o d \<Longrightarrow> a (b v) = c (d v)"
80 by (simp only: o_def) (fact fun_cong)
83 "a o b = c o d \<Longrightarrow> ((\<And>v. a (b v) = c (d v)) \<Longrightarrow> R) \<Longrightarrow> R"
84 by (erule meta_mp) (fact o_eq_dest)
86 lemma image_compose: "(f o g) ` r = f`(g`r)"
87 by (simp add: comp_def, blast)
89 lemma vimage_compose: "(g \<circ> f) -` x = f -` (g -` x)"
92 lemma UN_o: "UNION A (g o f) = UNION (f`A) g"
93 by (unfold comp_def, blast)
96 subsection {* The Forward Composition Operator @{text fcomp} *}
99 fcomp :: "('a \<Rightarrow> 'b) \<Rightarrow> ('b \<Rightarrow> 'c) \<Rightarrow> 'a \<Rightarrow> 'c" (infixl "\<circ>>" 60)
101 "f \<circ>> g = (\<lambda>x. g (f x))"
103 lemma fcomp_apply [simp]: "(f \<circ>> g) x = g (f x)"
104 by (simp add: fcomp_def)
106 lemma fcomp_assoc: "(f \<circ>> g) \<circ>> h = f \<circ>> (g \<circ>> h)"
107 by (simp add: fcomp_def)
109 lemma id_fcomp [simp]: "id \<circ>> g = g"
110 by (simp add: fcomp_def)
112 lemma fcomp_id [simp]: "f \<circ>> id = f"
113 by (simp add: fcomp_def)
118 no_notation fcomp (infixl "\<circ>>" 60)
121 subsection {* Mapping functions *}
123 definition map_fun :: "('c \<Rightarrow> 'a) \<Rightarrow> ('b \<Rightarrow> 'd) \<Rightarrow> ('a \<Rightarrow> 'b) \<Rightarrow> 'c \<Rightarrow> 'd" where
124 "map_fun f g h = g \<circ> h \<circ> f"
126 lemma map_fun_apply [simp]:
127 "map_fun f g h x = g (h (f x))"
128 by (simp add: map_fun_def)
131 subsection {* Injectivity and Bijectivity *}
133 definition inj_on :: "('a \<Rightarrow> 'b) \<Rightarrow> 'a set \<Rightarrow> bool" where -- "injective"
134 "inj_on f A \<longleftrightarrow> (\<forall>x\<in>A. \<forall>y\<in>A. f x = f y \<longrightarrow> x = y)"
136 definition bij_betw :: "('a \<Rightarrow> 'b) \<Rightarrow> 'a set \<Rightarrow> 'b set \<Rightarrow> bool" where -- "bijective"
137 "bij_betw f A B \<longleftrightarrow> inj_on f A \<and> f ` A = B"
139 text{*A common special case: functions injective, surjective or bijective over
140 the entire domain type.*}
143 "inj f \<equiv> inj_on f UNIV"
145 abbreviation surj :: "('a \<Rightarrow> 'b) \<Rightarrow> bool" where -- "surjective"
146 "surj f \<equiv> (range f = UNIV)"
149 "bij f \<equiv> bij_betw f UNIV UNIV"
152 assumes "\<And>x y. f x = f y \<Longrightarrow> x = y"
154 using assms unfolding inj_on_def by auto
156 theorem range_ex1_eq: "inj f \<Longrightarrow> b : range f = (EX! x. b = f x)"
157 by (unfold inj_on_def, blast)
159 lemma injD: "[| inj(f); f(x) = f(y) |] ==> x=y"
160 by (simp add: inj_on_def)
162 lemma inj_on_eq_iff: "inj_on f A ==> x:A ==> y:A ==> (f(x) = f(y)) = (x=y)"
163 by (force simp add: inj_on_def)
166 "(\<And> a. a : A \<Longrightarrow> f a = g a) \<Longrightarrow> inj_on f A = inj_on g A"
167 unfolding inj_on_def by auto
169 lemma inj_on_strict_subset:
170 "\<lbrakk> inj_on f B; A < B \<rbrakk> \<Longrightarrow> f`A < f`B"
171 unfolding inj_on_def unfolding image_def by blast
174 "inj f \<Longrightarrow> inj g \<Longrightarrow> inj (f \<circ> g)"
175 by (simp add: inj_on_def)
177 lemma inj_fun: "inj f \<Longrightarrow> inj (\<lambda>x y. f x)"
178 by (simp add: inj_on_def fun_eq_iff)
180 lemma inj_eq: "inj f ==> (f(x) = f(y)) = (x=y)"
181 by (simp add: inj_on_eq_iff)
183 lemma inj_on_id[simp]: "inj_on id A"
184 by (simp add: inj_on_def)
186 lemma inj_on_id2[simp]: "inj_on (%x. x) A"
187 by (simp add: inj_on_def)
189 lemma inj_on_Int: "\<lbrakk>inj_on f A; inj_on f B\<rbrakk> \<Longrightarrow> inj_on f (A \<inter> B)"
190 unfolding inj_on_def by blast
193 "\<lbrakk>I \<noteq> {}; \<And> i. i \<in> I \<Longrightarrow> inj_on f (A i)\<rbrakk> \<Longrightarrow> inj_on f (\<Inter> i \<in> I. A i)"
194 unfolding inj_on_def by blast
197 "\<lbrakk>S \<noteq> {}; \<And> A. A \<in> S \<Longrightarrow> inj_on f A\<rbrakk> \<Longrightarrow> inj_on f (Inter S)"
198 unfolding inj_on_def by blast
200 lemma inj_on_UNION_chain:
201 assumes CH: "\<And> i j. \<lbrakk>i \<in> I; j \<in> I\<rbrakk> \<Longrightarrow> A i \<le> A j \<or> A j \<le> A i" and
202 INJ: "\<And> i. i \<in> I \<Longrightarrow> inj_on f (A i)"
203 shows "inj_on f (\<Union> i \<in> I. A i)"
204 proof(unfold inj_on_def UNION_def, auto)
206 assume *: "i \<in> I" "j \<in> I" and **: "x \<in> A i" "y \<in> A j"
210 {assume "A i \<le> A j"
211 with ** have "x \<in> A j" by auto
212 with INJ * ** *** have ?thesis
213 by(auto simp add: inj_on_def)
216 {assume "A j \<le> A i"
217 with ** have "y \<in> A i" by auto
218 with INJ * ** *** have ?thesis
219 by(auto simp add: inj_on_def)
221 ultimately show ?thesis using CH * by blast
225 lemma surj_id: "surj id"
228 lemma bij_id[simp]: "bij id"
229 by (simp add: bij_betw_def)
232 "(!! x y. [| x:A; y:A; f(x) = f(y) |] ==> x=y) ==> inj_on f A"
233 by (simp add: inj_on_def)
235 lemma inj_on_inverseI: "(!!x. x:A ==> g(f(x)) = x) ==> inj_on f A"
236 by (auto dest: arg_cong [of concl: g] simp add: inj_on_def)
238 lemma inj_onD: "[| inj_on f A; f(x)=f(y); x:A; y:A |] ==> x=y"
239 by (unfold inj_on_def, blast)
241 lemma inj_on_iff: "[| inj_on f A; x:A; y:A |] ==> (f(x)=f(y)) = (x=y)"
242 by (blast dest!: inj_onD)
245 "[| inj_on f A; inj_on g (f`A) |] ==> inj_on (g o f) A"
246 by (simp add: comp_def inj_on_def)
248 lemma inj_on_imageI: "inj_on (g o f) A \<Longrightarrow> inj_on g (f ` A)"
249 apply(simp add:inj_on_def image_def)
253 lemma inj_on_image_iff: "\<lbrakk> ALL x:A. ALL y:A. (g(f x) = g(f y)) = (g x = g y);
254 inj_on f A \<rbrakk> \<Longrightarrow> inj_on g (f ` A) = inj_on g A"
255 apply(unfold inj_on_def)
259 lemma inj_on_contraD: "[| inj_on f A; ~x=y; x:A; y:A |] ==> ~ f(x)=f(y)"
260 by (unfold inj_on_def, blast)
262 lemma inj_singleton: "inj (%s. {s})"
263 by (simp add: inj_on_def)
265 lemma inj_on_empty[iff]: "inj_on f {}"
266 by(simp add: inj_on_def)
268 lemma subset_inj_on: "[| inj_on f B; A <= B |] ==> inj_on f A"
269 by (unfold inj_on_def, blast)
273 (inj_on f A & inj_on f B & f`(A-B) Int f`(B-A) = {})"
274 apply(unfold inj_on_def)
275 apply (blast intro:sym)
278 lemma inj_on_insert[iff]:
279 "inj_on f (insert a A) = (inj_on f A & f a ~: f`(A-{a}))"
280 apply(unfold inj_on_def)
281 apply (blast intro:sym)
284 lemma inj_on_diff: "inj_on f A ==> inj_on f (A-B)"
285 apply(unfold inj_on_def)
289 lemma comp_inj_on_iff:
290 "inj_on f A \<Longrightarrow> inj_on f' (f ` A) \<longleftrightarrow> inj_on (f' o f) A"
291 by(auto simp add: comp_inj_on inj_on_def)
293 lemma inj_on_imageI2:
294 "inj_on (f' o f) A \<Longrightarrow> inj_on f A"
295 by(auto simp add: comp_inj_on inj_on_def)
297 lemma surj_def: "surj f \<longleftrightarrow> (\<forall>y. \<exists>x. y = f x)"
300 lemma surjI: assumes *: "\<And> x. g (f x) = x" shows "surj g"
301 using *[symmetric] by auto
303 lemma surjD: "surj f \<Longrightarrow> \<exists>x. y = f x"
304 by (simp add: surj_def)
306 lemma surjE: "surj f \<Longrightarrow> (\<And>x. y = f x \<Longrightarrow> C) \<Longrightarrow> C"
307 by (simp add: surj_def, blast)
309 lemma comp_surj: "[| surj f; surj g |] ==> surj (g o f)"
310 apply (simp add: comp_def surj_def, clarify)
311 apply (drule_tac x = y in spec, clarify)
312 apply (drule_tac x = x in spec, blast)
315 lemma bij_betw_imp_surj: "bij_betw f A UNIV \<Longrightarrow> surj f"
316 unfolding bij_betw_def by auto
318 lemma bij_betw_empty1:
319 assumes "bij_betw f {} A"
321 using assms unfolding bij_betw_def by blast
323 lemma bij_betw_empty2:
324 assumes "bij_betw f A {}"
326 using assms unfolding bij_betw_def by blast
328 lemma inj_on_imp_bij_betw:
329 "inj_on f A \<Longrightarrow> bij_betw f A (f ` A)"
330 unfolding bij_betw_def by simp
332 lemma bij_def: "bij f \<longleftrightarrow> inj f \<and> surj f"
333 unfolding bij_betw_def ..
335 lemma bijI: "[| inj f; surj f |] ==> bij f"
336 by (simp add: bij_def)
338 lemma bij_is_inj: "bij f ==> inj f"
339 by (simp add: bij_def)
341 lemma bij_is_surj: "bij f ==> surj f"
342 by (simp add: bij_def)
344 lemma bij_betw_imp_inj_on: "bij_betw f A B \<Longrightarrow> inj_on f A"
345 by (simp add: bij_betw_def)
347 lemma bij_betw_trans:
348 "bij_betw f A B \<Longrightarrow> bij_betw g B C \<Longrightarrow> bij_betw (g o f) A C"
349 by(auto simp add:bij_betw_def comp_inj_on)
351 lemma bij_comp: "bij f \<Longrightarrow> bij g \<Longrightarrow> bij (g o f)"
352 by (rule bij_betw_trans)
354 lemma bij_betw_comp_iff:
355 "bij_betw f A A' \<Longrightarrow> bij_betw f' A' A'' \<longleftrightarrow> bij_betw (f' o f) A A''"
356 by(auto simp add: bij_betw_def inj_on_def)
358 lemma bij_betw_comp_iff2:
359 assumes BIJ: "bij_betw f' A' A''" and IM: "f ` A \<le> A'"
360 shows "bij_betw f A A' \<longleftrightarrow> bij_betw (f' o f) A A''"
362 proof(auto simp add: bij_betw_comp_iff)
363 assume *: "bij_betw (f' \<circ> f) A A''"
364 thus "bij_betw f A A'"
366 proof(auto simp add: bij_betw_def)
367 assume "inj_on (f' \<circ> f) A"
368 thus "inj_on f A" using inj_on_imageI2 by blast
370 fix a' assume **: "a' \<in> A'"
371 hence "f' a' \<in> A''" using BIJ unfolding bij_betw_def by auto
372 then obtain a where 1: "a \<in> A \<and> f'(f a) = f' a'" using *
373 unfolding bij_betw_def by force
374 hence "f a \<in> A'" using IM by auto
375 hence "f a = a'" using BIJ ** 1 unfolding bij_betw_def inj_on_def by auto
376 thus "a' \<in> f ` A" using 1 by auto
380 lemma bij_betw_inv: assumes "bij_betw f A B" shows "EX g. bij_betw g B A"
382 have i: "inj_on f A" and s: "f ` A = B"
383 using assms by(auto simp:bij_betw_def)
384 let ?P = "%b a. a:A \<and> f a = b" let ?g = "%b. The (?P b)"
385 { fix a b assume P: "?P b a"
386 hence ex1: "\<exists>a. ?P b a" using s unfolding image_def by blast
387 hence uex1: "\<exists>!a. ?P b a" by(blast dest:inj_onD[OF i])
388 hence " ?g b = a" using the1_equality[OF uex1, OF P] P by simp
392 fix x y assume "x:B" "y:B" "?g x = ?g y"
393 from s `x:B` obtain a1 where a1: "?P x a1" unfolding image_def by blast
394 from s `y:B` obtain a2 where a2: "?P y a2" unfolding image_def by blast
395 from g[OF a1] a1 g[OF a2] a2 `?g x = ?g y` show "x=y" by simp
397 moreover have "?g ` B = A"
398 proof(auto simp:image_def)
400 with s obtain a where P: "?P b a" unfolding image_def by blast
401 thus "?g b \<in> A" using g[OF P] by auto
404 then obtain b where P: "?P b a" using s unfolding image_def by blast
405 then have "b:B" using s unfolding image_def by blast
406 with g[OF P] show "\<exists>b\<in>B. a = ?g b" by blast
408 ultimately show ?thesis by(auto simp:bij_betw_def)
412 "(\<And> a. a \<in> A \<Longrightarrow> f a = g a) \<Longrightarrow> bij_betw f A A' = bij_betw g A A'"
413 unfolding bij_betw_def inj_on_def by force
415 lemma bij_betw_id[intro, simp]:
417 unfolding bij_betw_def id_def by auto
419 lemma bij_betw_id_iff:
420 "bij_betw id A B \<longleftrightarrow> A = B"
421 by(auto simp add: bij_betw_def)
423 lemma bij_betw_combine:
424 assumes "bij_betw f A B" "bij_betw f C D" "B \<inter> D = {}"
425 shows "bij_betw f (A \<union> C) (B \<union> D)"
426 using assms unfolding bij_betw_def inj_on_Un image_Un by auto
428 lemma bij_betw_UNION_chain:
429 assumes CH: "\<And> i j. \<lbrakk>i \<in> I; j \<in> I\<rbrakk> \<Longrightarrow> A i \<le> A j \<or> A j \<le> A i" and
430 BIJ: "\<And> i. i \<in> I \<Longrightarrow> bij_betw f (A i) (A' i)"
431 shows "bij_betw f (\<Union> i \<in> I. A i) (\<Union> i \<in> I. A' i)"
432 proof(unfold bij_betw_def, auto simp add: image_def)
433 have "\<And> i. i \<in> I \<Longrightarrow> inj_on f (A i)"
434 using BIJ bij_betw_def[of f] by auto
435 thus "inj_on f (\<Union> i \<in> I. A i)"
436 using CH inj_on_UNION_chain[of I A f] by auto
439 assume *: "i \<in> I" "x \<in> A i"
440 hence "f x \<in> A' i" using BIJ bij_betw_def[of f] by auto
441 thus "\<exists>j \<in> I. f x \<in> A' j" using * by blast
444 assume *: "i \<in> I" "x' \<in> A' i"
445 hence "\<exists>x \<in> A i. x' = f x" using BIJ bij_betw_def[of f] by blast
446 thus "\<exists>j \<in> I. \<exists>x \<in> A j. x' = f x"
450 lemma bij_betw_Disj_Un:
451 assumes DISJ: "A \<inter> B = {}" and DISJ': "A' \<inter> B' = {}" and
452 B1: "bij_betw f A A'" and B2: "bij_betw f B B'"
453 shows "bij_betw f (A \<union> B) (A' \<union> B')"
455 have 1: "inj_on f A \<and> inj_on f B"
456 using B1 B2 by (auto simp add: bij_betw_def)
457 have 2: "f`A = A' \<and> f`B = B'"
458 using B1 B2 by (auto simp add: bij_betw_def)
459 hence "f`(A - B) \<inter> f`(B - A) = {}"
460 using DISJ DISJ' by blast
461 hence "inj_on f (A \<union> B)"
462 using 1 by (auto simp add: inj_on_Un)
465 have "f`(A \<union> B) = A' \<union> B'"
467 ultimately show ?thesis
468 unfolding bij_betw_def by auto
471 lemma bij_betw_subset:
472 assumes BIJ: "bij_betw f A A'" and
473 SUB: "B \<le> A" and IM: "f ` B = B'"
474 shows "bij_betw f B B'"
476 by(unfold bij_betw_def inj_on_def, auto simp add: inj_on_def)
478 lemma surj_image_vimage_eq: "surj f ==> f ` (f -` A) = A"
481 lemma inj_vimage_image_eq: "inj f ==> f -` (f ` A) = A"
482 by (simp add: inj_on_def, blast)
484 lemma vimage_subsetD: "surj f ==> f -` B <= A ==> B <= f ` A"
485 by (blast intro: sym)
487 lemma vimage_subsetI: "inj f ==> B <= f ` A ==> f -` B <= A"
488 by (unfold inj_on_def, blast)
490 lemma vimage_subset_eq: "bij f ==> (f -` B <= A) = (B <= f ` A)"
491 apply (unfold bij_def)
492 apply (blast del: subsetI intro: vimage_subsetI vimage_subsetD)
495 lemma inj_on_Un_image_eq_iff: "inj_on f (A \<union> B) \<Longrightarrow> f ` A = f ` B \<longleftrightarrow> A = B"
496 by(blast dest: inj_onD)
498 lemma inj_on_image_Int:
499 "[| inj_on f C; A<=C; B<=C |] ==> f`(A Int B) = f`A Int f`B"
500 apply (simp add: inj_on_def, blast)
503 lemma inj_on_image_set_diff:
504 "[| inj_on f C; A<=C; B<=C |] ==> f`(A-B) = f`A - f`B"
505 apply (simp add: inj_on_def, blast)
508 lemma image_Int: "inj f ==> f`(A Int B) = f`A Int f`B"
509 by (simp add: inj_on_def, blast)
511 lemma image_set_diff: "inj f ==> f`(A-B) = f`A - f`B"
512 by (simp add: inj_on_def, blast)
514 lemma inj_image_mem_iff: "inj f ==> (f a : f`A) = (a : A)"
515 by (blast dest: injD)
517 lemma inj_image_subset_iff: "inj f ==> (f`A <= f`B) = (A<=B)"
518 by (simp add: inj_on_def, blast)
520 lemma inj_image_eq_iff: "inj f ==> (f`A = f`B) = (A = B)"
521 by (blast dest: injD)
523 (*injectivity's required. Left-to-right inclusion holds even if A is empty*)
525 "[| inj_on f C; ALL x:A. B x <= C; j:A |]
526 ==> f ` (INTER A B) = (INT x:A. f ` B x)"
527 apply (simp add: inj_on_def, blast)
530 (*Compare with image_INT: no use of inj_on, and if f is surjective then
531 it doesn't matter whether A is empty*)
532 lemma bij_image_INT: "bij f ==> f ` (INTER A B) = (INT x:A. f ` B x)"
533 apply (simp add: bij_def)
534 apply (simp add: inj_on_def surj_def, blast)
537 lemma surj_Compl_image_subset: "surj f ==> -(f`A) <= f`(-A)"
540 lemma inj_image_Compl_subset: "inj f ==> f`(-A) <= -(f`A)"
541 by (auto simp add: inj_on_def)
543 lemma bij_image_Compl_eq: "bij f ==> f`(-A) = -(f`A)"
544 apply (simp add: bij_def)
545 apply (rule equalityI)
546 apply (simp_all (no_asm_simp) add: inj_image_Compl_subset surj_Compl_image_subset)
549 lemma inj_vimage_singleton: "inj f \<Longrightarrow> f -` {a} \<subseteq> {THE x. f x = a}"
550 -- {* The inverse image of a singleton under an injective function
551 is included in a singleton. *}
552 apply (auto simp add: inj_on_def)
553 apply (blast intro: the_equality [symmetric])
556 lemma (in ordered_ab_group_add) inj_uminus[simp, intro]: "inj_on uminus A"
557 by (auto intro!: inj_onI)
559 lemma (in linorder) strict_mono_imp_inj_on: "strict_mono f \<Longrightarrow> inj_on f A"
560 by (auto intro!: inj_onI dest: strict_mono_eq)
563 subsection{*Function Updating*}
566 fun_upd :: "('a => 'b) => 'a => 'b => ('a => 'b)" where
567 "fun_upd f a b == % x. if x=a then b else f x"
569 nonterminal updbinds and updbind
572 "_updbind" :: "['a, 'a] => updbind" ("(2_ :=/ _)")
573 "" :: "updbind => updbinds" ("_")
574 "_updbinds":: "[updbind, updbinds] => updbinds" ("_,/ _")
575 "_Update" :: "['a, updbinds] => 'a" ("_/'((_)')" [1000, 0] 900)
578 "_Update f (_updbinds b bs)" == "_Update (_Update f b) bs"
579 "f(x:=y)" == "CONST fun_upd f x y"
581 (* Hint: to define the sum of two functions (or maps), use sum_case.
582 A nice infix syntax could be defined (in Datatype.thy or below) by
584 sum_case (infixr "'(+')"80)
587 lemma fun_upd_idem_iff: "(f(x:=y) = f) = (f x = y)"
588 apply (simp add: fun_upd_def, safe)
590 apply (rule_tac [2] ext, auto)
593 (* f x = y ==> f(x:=y) = f *)
594 lemmas fun_upd_idem = fun_upd_idem_iff [THEN iffD2, standard]
596 (* f(x := f x) = f *)
597 lemmas fun_upd_triv = refl [THEN fun_upd_idem]
598 declare fun_upd_triv [iff]
600 lemma fun_upd_apply [simp]: "(f(x:=y))z = (if z=x then y else f z)"
601 by (simp add: fun_upd_def)
603 (* fun_upd_apply supersedes these two, but they are useful
604 if fun_upd_apply is intentionally removed from the simpset *)
605 lemma fun_upd_same: "(f(x:=y)) x = y"
608 lemma fun_upd_other: "z~=x ==> (f(x:=y)) z = f z"
611 lemma fun_upd_upd [simp]: "f(x:=y,x:=z) = f(x:=z)"
612 by (simp add: fun_eq_iff)
614 lemma fun_upd_twist: "a ~= c ==> (m(a:=b))(c:=d) = (m(c:=d))(a:=b)"
617 lemma inj_on_fun_updI: "\<lbrakk> inj_on f A; y \<notin> f`A \<rbrakk> \<Longrightarrow> inj_on (f(x:=y)) A"
618 by (fastsimp simp:inj_on_def image_def)
621 "f(x:=y) ` A = (if x \<in> A then insert y (f ` (A-{x})) else f ` A)"
624 lemma fun_upd_comp: "f \<circ> (g(x := y)) = (f \<circ> g)(x := f y)"
628 subsection {* @{text override_on} *}
631 override_on :: "('a \<Rightarrow> 'b) \<Rightarrow> ('a \<Rightarrow> 'b) \<Rightarrow> 'a set \<Rightarrow> 'a \<Rightarrow> 'b"
633 "override_on f g A = (\<lambda>a. if a \<in> A then g a else f a)"
635 lemma override_on_emptyset[simp]: "override_on f g {} = f"
636 by(simp add:override_on_def)
638 lemma override_on_apply_notin[simp]: "a ~: A ==> (override_on f g A) a = f a"
639 by(simp add:override_on_def)
641 lemma override_on_apply_in[simp]: "a : A ==> (override_on f g A) a = g a"
642 by(simp add:override_on_def)
645 subsection {* @{text swap} *}
648 swap :: "'a \<Rightarrow> 'a \<Rightarrow> ('a \<Rightarrow> 'b) \<Rightarrow> ('a \<Rightarrow> 'b)"
650 "swap a b f = f (a := f b, b:= f a)"
652 lemma swap_self [simp]: "swap a a f = f"
653 by (simp add: swap_def)
655 lemma swap_commute: "swap a b f = swap b a f"
656 by (rule ext, simp add: fun_upd_def swap_def)
658 lemma swap_nilpotent [simp]: "swap a b (swap a b f) = f"
659 by (rule ext, simp add: fun_upd_def swap_def)
662 assumes "a \<noteq> c" and "b \<noteq> c"
663 shows "swap a b (swap b c (swap a b f)) = swap a c f"
664 using assms by (simp add: fun_eq_iff swap_def)
666 lemma comp_swap: "f \<circ> swap a b g = swap a b (f \<circ> g)"
667 by (rule ext, simp add: fun_upd_def swap_def)
669 lemma swap_image_eq [simp]:
670 assumes "a \<in> A" "b \<in> A" shows "swap a b f ` A = f ` A"
672 have subset: "\<And>f. swap a b f ` A \<subseteq> f ` A"
673 using assms by (auto simp: image_iff swap_def)
674 then have "swap a b (swap a b f) ` A \<subseteq> (swap a b f) ` A" .
675 with subset[of f] show ?thesis by auto
678 lemma inj_on_imp_inj_on_swap:
679 "\<lbrakk>inj_on f A; a \<in> A; b \<in> A\<rbrakk> \<Longrightarrow> inj_on (swap a b f) A"
680 by (simp add: inj_on_def swap_def, blast)
682 lemma inj_on_swap_iff [simp]:
683 assumes A: "a \<in> A" "b \<in> A" shows "inj_on (swap a b f) A \<longleftrightarrow> inj_on f A"
685 assume "inj_on (swap a b f) A"
686 with A have "inj_on (swap a b (swap a b f)) A"
687 by (iprover intro: inj_on_imp_inj_on_swap)
688 thus "inj_on f A" by simp
691 with A show "inj_on (swap a b f) A" by (iprover intro: inj_on_imp_inj_on_swap)
694 lemma surj_imp_surj_swap: "surj f \<Longrightarrow> surj (swap a b f)"
697 lemma surj_swap_iff [simp]: "surj (swap a b f) \<longleftrightarrow> surj f"
700 lemma bij_betw_swap_iff [simp]:
701 "\<lbrakk> x \<in> A; y \<in> A \<rbrakk> \<Longrightarrow> bij_betw (swap x y f) A B \<longleftrightarrow> bij_betw f A B"
702 by (auto simp: bij_betw_def)
704 lemma bij_swap_iff [simp]: "bij (swap a b f) \<longleftrightarrow> bij f"
707 hide_const (open) swap
709 subsection {* Inversion of injective functions *}
711 definition the_inv_into :: "'a set => ('a => 'b) => ('b => 'a)" where
712 "the_inv_into A f == %x. THE y. y : A & f y = x"
714 lemma the_inv_into_f_f:
715 "[| inj_on f A; x : A |] ==> the_inv_into A f (f x) = x"
716 apply (simp add: the_inv_into_def inj_on_def)
720 lemma f_the_inv_into_f:
721 "inj_on f A ==> y : f`A ==> f (the_inv_into A f y) = y"
722 apply (simp add: the_inv_into_def)
724 apply(blast dest: inj_onD)
728 lemma the_inv_into_into:
729 "[| inj_on f A; x : f ` A; A <= B |] ==> the_inv_into A f x : B"
730 apply (simp add: the_inv_into_def)
732 apply(blast dest: inj_onD)
736 lemma the_inv_into_onto[simp]:
737 "inj_on f A ==> the_inv_into A f ` (f ` A) = A"
738 by (fast intro:the_inv_into_into the_inv_into_f_f[symmetric])
740 lemma the_inv_into_f_eq:
741 "[| inj_on f A; f x = y; x : A |] ==> the_inv_into A f y = x"
743 apply (erule the_inv_into_f_f, assumption)
746 lemma the_inv_into_comp:
747 "[| inj_on f (g ` A); inj_on g A; x : f ` g ` A |] ==>
748 the_inv_into A (f o g) x = (the_inv_into A g o the_inv_into (g ` A) f) x"
749 apply (rule the_inv_into_f_eq)
750 apply (fast intro: comp_inj_on)
751 apply (simp add: f_the_inv_into_f the_inv_into_into)
752 apply (simp add: the_inv_into_into)
755 lemma inj_on_the_inv_into:
756 "inj_on f A \<Longrightarrow> inj_on (the_inv_into A f) (f ` A)"
757 by (auto intro: inj_onI simp: image_def the_inv_into_f_f)
759 lemma bij_betw_the_inv_into:
760 "bij_betw f A B \<Longrightarrow> bij_betw (the_inv_into A f) B A"
761 by (auto simp add: bij_betw_def inj_on_the_inv_into the_inv_into_into)
763 abbreviation the_inv :: "('a \<Rightarrow> 'b) \<Rightarrow> ('b \<Rightarrow> 'a)" where
764 "the_inv f \<equiv> the_inv_into UNIV f"
768 shows "the_inv f (f x) = x" using assms UNIV_I
769 by (rule the_inv_into_f_f)
771 subsection {* Cantor's Paradox *}
773 lemma Cantors_paradox:
774 "\<not>(\<exists>f. f ` A = Pow A)"
776 fix f assume "f ` A = Pow A" hence *: "Pow A \<le> f ` A" by blast
777 let ?X = "{a \<in> A. a \<notin> f a}"
778 have "?X \<in> Pow A" unfolding Pow_def by auto
779 with * obtain x where "x \<in> A \<and> f x = ?X" by blast
783 subsection {* Setup *}
785 subsubsection {* Proof tools *}
787 text {* simplifies terms of the form
788 f(...,x:=y,...,x:=z,...) to f(...,x:=z,...) *}
790 simproc_setup fun_upd2 ("f(v := w, x := y)") = {* fn _ =>
792 fun gen_fun_upd NONE T _ _ = NONE
793 | gen_fun_upd (SOME f) T x y = SOME (Const (@{const_name fun_upd}, T) $ f $ x $ y)
794 fun dest_fun_T1 (Type (_, T :: Ts)) = T
795 fun find_double (t as Const (@{const_name fun_upd},T) $ f $ x $ y) =
797 fun find (Const (@{const_name fun_upd},T) $ g $ v $ w) =
798 if v aconv x then SOME g else gen_fun_upd (find g) T v w
800 in (dest_fun_T1 T, gen_fun_upd (find f) T x y) end
804 val ctxt = Simplifier.the_context ss
805 val t = Thm.term_of ct
807 case find_double t of
810 SOME (Goal.prove ctxt [] [] (Logic.mk_equals (t, rhs))
812 rtac eq_reflection 1 THEN
814 simp_tac (Simplifier.inherit_context ss @{simpset}) 1))
820 subsubsection {* Code generator *}
825 fun term_of_fun_type _ aT _ bT _ = Free ("<function>", aT --> bT);
828 fun gen_fun_type aF aT bG bT i =
830 val tab = Unsynchronized.ref [];
831 fun mk_upd (x, (_, y)) t = Const ("Fun.fun_upd",
832 (aT --> bT) --> aT --> bT --> aT --> bT) $ t $ aF x $ y ()
835 case AList.lookup op = (!tab) x of
837 let val p as (y, _) = bG i
838 in (tab := (x, p) :: !tab; y) end
840 fn () => Basics.fold mk_upd (!tab) (Const ("HOL.undefined", aT --> bT)))
844 code_const "op \<circ>"
846 (Haskell infixr 9 ".")
852 subsubsection {* Functorial structure of types *}
854 use "Tools/enriched_type.ML"