1 (* ========================================================================= *)
2 (* Basic notions of cardinal arithmetic. *)
3 (* ========================================================================= *)
5 needs "Library/wo.ml";;
7 let TRANS_CHAIN_TAC th =
8 MAP_EVERY (fun t -> TRANS_TAC th t THEN ASM_REWRITE_TAC[]);;
10 (* ------------------------------------------------------------------------- *)
11 (* We need these a few times, so give them names. *)
12 (* ------------------------------------------------------------------------- *)
14 let sum_DISTINCT = distinctness "sum";;
16 let sum_INJECTIVE = injectivity "sum";;
18 let sum_CASES = prove_cases_thm sum_INDUCT;;
20 let FORALL_SUM_THM = prove
21 (`(!z. P z) <=> (!x. P(INL x)) /\ (!x. P(INR x))`,
22 MESON_TAC[sum_CASES]);;
24 let EXISTS_SUM_THM = prove
25 (`(?z. P z) <=> (?x. P(INL x)) \/ (?x. P(INR x))`,
26 MESON_TAC[sum_CASES]);;
28 (* ------------------------------------------------------------------------- *)
29 (* Special case of Zorn's Lemma for restriction of subset lattice. *)
30 (* ------------------------------------------------------------------------- *)
32 let POSET_RESTRICTED_SUBSET = prove
33 (`!P. poset(\(x,y). P(x) /\ P(y) /\ x SUBSET y)`,
34 GEN_TAC THEN REWRITE_TAC[poset; fl] THEN
35 CONV_TAC(ONCE_DEPTH_CONV GEN_BETA_CONV) THEN
36 REWRITE_TAC[SUBSET; EXTENSION] THEN MESON_TAC[]);;
38 let FL_RESTRICTED_SUBSET = prove
39 (`!P. fl(\(x,y). P(x) /\ P(y) /\ x SUBSET y) = P`,
40 REWRITE_TAC[fl; FORALL_PAIR_THM; FUN_EQ_THM] THEN
41 CONV_TAC(ONCE_DEPTH_CONV GEN_BETA_CONV) THEN MESON_TAC[SUBSET_REFL]);;
43 let ZL_SUBSETS = prove
44 (`!P. (!c. (!x. x IN c ==> P x) /\
45 (!x y. x IN c /\ y IN c ==> x SUBSET y \/ y SUBSET x)
46 ==> ?z. P z /\ (!x. x IN c ==> x SUBSET z))
47 ==> ?a:A->bool. P a /\ (!x. P x /\ a SUBSET x ==> (a = x))`,
49 MP_TAC(ISPEC `\(x,y). P(x:A->bool) /\ P(y) /\ x SUBSET y` ZL) THEN
50 REWRITE_TAC[POSET_RESTRICTED_SUBSET; FL_RESTRICTED_SUBSET] THEN
51 REWRITE_TAC[chain] THEN
52 CONV_TAC(ONCE_DEPTH_CONV GEN_BETA_CONV) THEN
53 REWRITE_TAC[IN] THEN MATCH_MP_TAC MONO_IMP THEN CONJ_TAC THENL
54 [MATCH_MP_TAC MONO_FORALL; ALL_TAC] THEN
57 let ZL_SUBSETS_UNIONS = prove
58 (`!P. (!c. (!x. x IN c ==> P x) /\
59 (!x y. x IN c /\ y IN c ==> x SUBSET y \/ y SUBSET x)
61 ==> ?a:A->bool. P a /\ (!x. P x /\ a SUBSET x ==> (a = x))`,
62 REPEAT STRIP_TAC THEN MATCH_MP_TAC ZL_SUBSETS THEN
63 REPEAT STRIP_TAC THEN EXISTS_TAC `UNIONS(c:(A->bool)->bool)` THEN
64 ASM_MESON_TAC[SUBSET; IN_UNIONS]);;
66 let ZL_SUBSETS_UNIONS_NONEMPTY = prove
69 (!x. x IN c ==> P x) /\
70 (!x y. x IN c /\ y IN c ==> x SUBSET y \/ y SUBSET x)
72 ==> ?a:A->bool. P a /\ (!x. P x /\ a SUBSET x ==> (a = x))`,
73 REPEAT STRIP_TAC THEN MATCH_MP_TAC ZL_SUBSETS THEN
74 REPEAT STRIP_TAC THEN ASM_CASES_TAC `?x:A->bool. x IN c` THENL
75 [EXISTS_TAC `UNIONS(c:(A->bool)->bool)` THEN
76 ASM_SIMP_TAC[] THEN MESON_TAC[SUBSET; IN_UNIONS];
79 (* ------------------------------------------------------------------------- *)
80 (* Useful lemma to reduce some higher order stuff to first order. *)
81 (* ------------------------------------------------------------------------- *)
83 let FLATTEN_LEMMA = prove
84 (`(!x. x IN s ==> (g(f(x)) = x)) <=> !y x. x IN s /\ (y = f x) ==> (g y = x)`,
87 (* ------------------------------------------------------------------------- *)
88 (* Knaster-Tarski fixpoint theorem (used in Schroeder-Bernstein below). *)
89 (* ------------------------------------------------------------------------- *)
91 let TARSKI_SET = prove
92 (`!f. (!s t. s SUBSET t ==> f(s) SUBSET f(t)) ==> ?s:A->bool. f(s) = s`,
93 REPEAT STRIP_TAC THEN MAP_EVERY ABBREV_TAC
94 [`Y = {b:A->bool | f(b) SUBSET b}`; `a:A->bool = INTERS Y`] THEN
95 SUBGOAL_THEN `!b:A->bool. b IN Y <=> f(b) SUBSET b` ASSUME_TAC THENL
96 [EXPAND_TAC "Y" THEN REWRITE_TAC[IN_ELIM_THM]; ALL_TAC] THEN
97 SUBGOAL_THEN `!b:A->bool. b IN Y ==> f(a:A->bool) SUBSET b` ASSUME_TAC THENL
98 [ASM_MESON_TAC[SUBSET_TRANS; IN_INTERS; SUBSET]; ALL_TAC] THEN
99 SUBGOAL_THEN `f(a:A->bool) SUBSET a`
100 (fun th -> ASM_MESON_TAC[SUBSET_ANTISYM; IN_INTERS; th]) THEN
101 ASM_MESON_TAC[IN_INTERS; SUBSET]);;
103 (* ------------------------------------------------------------------------- *)
104 (* We need a nonemptiness hypothesis for the nicest total function form. *)
105 (* ------------------------------------------------------------------------- *)
107 let INJECTIVE_LEFT_INVERSE_NONEMPTY = prove
109 ==> ((!x y. x IN s /\ y IN s /\ (f(x) = f(y)) ==> (x = y)) <=>
110 ?g. (!y. y IN t ==> g(y) IN s) /\
111 (!x. x IN s ==> (g(f(x)) = x)))`,
112 REWRITE_TAC[FLATTEN_LEMMA; GSYM SKOLEM_THM; AND_FORALL_THM] THEN
115 (* ------------------------------------------------------------------------- *)
116 (* Now bijectivity. *)
117 (* ------------------------------------------------------------------------- *)
119 let BIJECTIVE_INJECTIVE_SURJECTIVE = prove
120 (`(!x. x IN s ==> f(x) IN t) /\
121 (!y. y IN t ==> ?!x. x IN s /\ (f x = y)) <=>
122 (!x. x IN s ==> f(x) IN t) /\
123 (!x y. x IN s /\ y IN s /\ (f(x) = f(y)) ==> (x = y)) /\
124 (!y. y IN t ==> ?x. x IN s /\ (f x = y))`,
127 let BIJECTIVE_INVERSES = prove
128 (`(!x. x IN s ==> f(x) IN t) /\
129 (!y. y IN t ==> ?!x. x IN s /\ (f x = y)) <=>
130 (!x. x IN s ==> f(x) IN t) /\
131 ?g. (!y. y IN t ==> g(y) IN s) /\
132 (!y. y IN t ==> (f(g(y)) = y)) /\
133 (!x. x IN s ==> (g(f(x)) = x))`,
134 REWRITE_TAC[BIJECTIVE_INJECTIVE_SURJECTIVE;
135 INJECTIVE_ON_LEFT_INVERSE;
136 SURJECTIVE_ON_RIGHT_INVERSE] THEN
137 MATCH_MP_TAC(TAUT `(a ==> (b <=> c)) ==> (a /\ b <=> a /\ c)`) THEN
138 DISCH_TAC THEN REWRITE_TAC[RIGHT_AND_EXISTS_THM] THEN
139 AP_TERM_TAC THEN ABS_TAC THEN EQ_TAC THEN ASM_MESON_TAC[]);;
141 (* ------------------------------------------------------------------------- *)
142 (* Other variants of cardinal equality. *)
143 (* ------------------------------------------------------------------------- *)
145 let EQ_C_BIJECTIONS = prove
146 (`!s:A->bool t:B->bool.
147 s =_c t <=> ?f g. (!x. x IN s ==> f x IN t /\ g(f x) = x) /\
148 (!y. y IN t ==> g y IN s /\ f(g y) = y)`,
149 REPEAT GEN_TAC THEN REWRITE_TAC[eq_c] THEN
150 AP_TERM_TAC THEN GEN_REWRITE_TAC I [FUN_EQ_THM] THEN
151 X_GEN_TAC `f:A->B` THEN REWRITE_TAC[] THEN
152 EQ_TAC THENL [STRIP_TAC; MESON_TAC[]] THEN
153 EXISTS_TAC `(\y. @x. x IN s /\ f x = y):B->A` THEN
158 ?R:A#B->bool. (!x y. R(x,y) ==> x IN s /\ y IN t) /\
159 (!x. x IN s ==> ?!y. y IN t /\ R(x,y)) /\
160 (!y. y IN t ==> ?!x. x IN s /\ R(x,y))`,
161 REWRITE_TAC[eq_c] THEN EQ_TAC THENL
162 [DISCH_THEN(X_CHOOSE_THEN `f:A->B` STRIP_ASSUME_TAC) THEN
163 EXISTS_TAC `\(x:A,y:B). x IN s /\ y IN t /\ (y = f x)` THEN
164 CONV_TAC(ONCE_DEPTH_CONV GEN_BETA_CONV) THEN ASM_MESON_TAC[];
165 DISCH_THEN(CHOOSE_THEN (CONJUNCTS_THEN2 ASSUME_TAC MP_TAC)) THEN
166 DISCH_THEN(CONJUNCTS_THEN2 MP_TAC ASSUME_TAC) THEN
167 GEN_REWRITE_TAC (LAND_CONV o TOP_DEPTH_CONV)
168 [EXISTS_UNIQUE_ALT; RIGHT_IMP_EXISTS_THM; SKOLEM_THM] THEN
169 MATCH_MP_TAC MONO_EXISTS THEN ASM_MESON_TAC[]]);;
171 (* ------------------------------------------------------------------------- *)
172 (* The "easy" ordering properties. *)
173 (* ------------------------------------------------------------------------- *)
175 let CARD_LE_REFL = prove
176 (`!s:A->bool. s <=_c s`,
177 GEN_TAC THEN REWRITE_TAC[le_c] THEN EXISTS_TAC `\x:A. x` THEN SIMP_TAC[]);;
179 let CARD_LE_TRANS = prove
180 (`!s:A->bool t:B->bool u:C->bool.
181 s <=_c t /\ t <=_c u ==> s <=_c u`,
182 REPEAT GEN_TAC THEN REWRITE_TAC[le_c] THEN
183 DISCH_THEN(CONJUNCTS_THEN2
184 (X_CHOOSE_TAC `f:A->B`) (X_CHOOSE_TAC `g:B->C`)) THEN
185 EXISTS_TAC `(g:B->C) o (f:A->B)` THEN REWRITE_TAC[o_THM] THEN
188 let CARD_LT_REFL = prove
189 (`!s:A->bool. ~(s <_c s)`,
190 MESON_TAC[lt_c; CARD_LE_REFL]);;
192 let CARD_LET_TRANS = prove
193 (`!s:A->bool t:B->bool u:C->bool.
194 s <=_c t /\ t <_c u ==> s <_c u`,
195 REPEAT GEN_TAC THEN REWRITE_TAC[lt_c] THEN
196 MATCH_MP_TAC(TAUT `(a /\ b ==> c) /\ (c' /\ a ==> b')
197 ==> a /\ b /\ ~b' ==> c /\ ~c'`) THEN
198 REWRITE_TAC[CARD_LE_TRANS]);;
200 let CARD_LTE_TRANS = prove
201 (`!s:A->bool t:B->bool u:C->bool.
202 s <_c t /\ t <=_c u ==> s <_c u`,
203 REPEAT GEN_TAC THEN REWRITE_TAC[lt_c] THEN
204 MATCH_MP_TAC(TAUT `(a /\ b ==> c) /\ (b /\ c' ==> a')
205 ==> (a /\ ~a') /\ b ==> c /\ ~c'`) THEN
206 REWRITE_TAC[CARD_LE_TRANS]);;
208 let CARD_LT_TRANS = prove
209 (`!s:A->bool t:B->bool u:C->bool.
210 s <_c t /\ t <_c u ==> s <_c u`,
211 MESON_TAC[lt_c; CARD_LTE_TRANS]);;
213 let CARD_EQ_REFL = prove
214 (`!s:A->bool. s =_c s`,
215 GEN_TAC THEN REWRITE_TAC[eq_c] THEN EXISTS_TAC `\x:A. x` THEN
216 SIMP_TAC[] THEN MESON_TAC[]);;
218 let CARD_EQ_SYM = prove
219 (`!s t. s =_c t <=> t =_c s`,
220 REPEAT GEN_TAC THEN REWRITE_TAC[eq_c; BIJECTIVE_INVERSES] THEN
221 REWRITE_TAC[RIGHT_AND_EXISTS_THM] THEN
222 GEN_REWRITE_TAC RAND_CONV [SWAP_EXISTS_THM] THEN
223 REPEAT(AP_TERM_TAC THEN ABS_TAC) THEN REWRITE_TAC[CONJ_ACI]);;
225 let CARD_EQ_IMP_LE = prove
226 (`!s t. s =_c t ==> s <=_c t`,
227 REWRITE_TAC[le_c; eq_c] THEN MESON_TAC[]);;
229 let CARD_LT_IMP_LE = prove
230 (`!s t. s <_c t ==> s <=_c t`,
233 let CARD_LE_RELATIONAL = prove
235 (!x y y'. x IN s /\ R x y /\ R x y' ==> y = y')
236 ==> {y | ?x. x IN s /\ R x y} <=_c s`,
237 REPEAT STRIP_TAC THEN REWRITE_TAC[le_c] THEN
238 EXISTS_TAC `\y:B. @x:A. x IN s /\ R x y` THEN
239 REWRITE_TAC[IN_ELIM_THM] THEN ASM_MESON_TAC[]);;
241 let CARD_LE_RELATIONAL_FULL = prove
243 (!y. y IN t ==> ?x. x IN s /\ R x y) /\
244 (!x y y'. x IN s /\ y IN t /\ y' IN t /\ R x y /\ R x y' ==> y = y')
246 REPEAT STRIP_TAC THEN REWRITE_TAC[le_c] THEN
247 EXISTS_TAC `\y:B. @x:A. x IN s /\ R x y` THEN
248 REWRITE_TAC[IN_ELIM_THM] THEN ASM_MESON_TAC[]);;
250 (* ------------------------------------------------------------------------- *)
251 (* Two trivial lemmas. *)
252 (* ------------------------------------------------------------------------- *)
254 let CARD_LE_EMPTY = prove
255 (`!s. s <=_c {} <=> s = {}`,
256 REWRITE_TAC[le_c; EXTENSION; NOT_IN_EMPTY] THEN MESON_TAC[]);;
258 let CARD_EQ_EMPTY = prove
259 (`!s. s =_c {} <=> s = {}`,
260 REWRITE_TAC[eq_c; EXTENSION; NOT_IN_EMPTY] THEN MESON_TAC[]);;
262 (* ------------------------------------------------------------------------- *)
263 (* Antisymmetry (the Schroeder-Bernstein theorem). *)
264 (* ------------------------------------------------------------------------- *)
266 let CARD_LE_ANTISYM = prove
267 (`!s:A->bool t:B->bool. s <=_c t /\ t <=_c s <=> (s =_c t)`,
268 REPEAT GEN_TAC THEN EQ_TAC THENL
270 SIMP_TAC[CARD_EQ_IMP_LE] THEN ONCE_REWRITE_TAC[CARD_EQ_SYM] THEN
271 SIMP_TAC[CARD_EQ_IMP_LE]] THEN
272 ASM_CASES_TAC `s:A->bool = {}` THEN ASM_CASES_TAC `t:B->bool = {}` THEN
273 ASM_SIMP_TAC[CARD_LE_EMPTY; CARD_EQ_EMPTY] THEN
274 RULE_ASSUM_TAC(REWRITE_RULE[EXTENSION; NOT_IN_EMPTY; NOT_FORALL_THM]) THEN
275 ASM_SIMP_TAC[le_c; eq_c; INJECTIVE_LEFT_INVERSE_NONEMPTY] THEN
276 DISCH_THEN(CONJUNCTS_THEN2
277 (X_CHOOSE_THEN `i:A->B`
278 (CONJUNCTS_THEN2 ASSUME_TAC (X_CHOOSE_THEN `i':B->A` STRIP_ASSUME_TAC)))
279 (X_CHOOSE_THEN `j:B->A`
280 (CONJUNCTS_THEN2 ASSUME_TAC
281 (X_CHOOSE_THEN `j':A->B` STRIP_ASSUME_TAC)))) THEN
283 `\a. s DIFF (IMAGE (j:B->A) (t DIFF (IMAGE (i:A->B) a)))`
285 REWRITE_TAC[] THEN ANTS_TAC THENL
286 [REWRITE_TAC[SUBSET; IN_DIFF; IN_IMAGE] THEN MESON_TAC[];
288 DISCH_THEN(X_CHOOSE_THEN `a:A->bool` ASSUME_TAC) THEN
289 REWRITE_TAC[BIJECTIVE_INVERSES] THEN REWRITE_TAC[RIGHT_AND_EXISTS_THM] THEN
290 EXISTS_TAC `\x. if x IN a then (i:A->B)(x) else j'(x)` THEN
291 EXISTS_TAC `\y. if y IN (IMAGE (i:A->B) a) then i'(y) else (j:B->A)(y)` THEN
292 REWRITE_TAC[FUN_EQ_THM; o_THM; I_DEF] THEN
293 ONCE_REWRITE_TAC[TAUT `a /\ b /\ c /\ d <=> (a /\ d) /\ (b /\ c)`] THEN
294 REWRITE_TAC[AND_FORALL_THM] THEN
295 REWRITE_TAC[TAUT `(a ==> b) /\ (a ==> c) <=> a ==> b /\ c`] THEN
297 [X_GEN_TAC `x:A` THEN ASM_CASES_TAC `x:A IN a`;
298 X_GEN_TAC `y:B` THEN ASM_CASES_TAC `y IN IMAGE (i:A->B) a`] THEN
299 ASM_REWRITE_TAC[] THEN COND_CASES_TAC THEN ASM_REWRITE_TAC[] THEN
300 RULE_ASSUM_TAC(REWRITE_RULE[EXTENSION; IN_UNIV; IN_DIFF; IN_IMAGE]) THEN
301 TRY(FIRST_X_ASSUM(X_CHOOSE_THEN `x:A` STRIP_ASSUME_TAC)) THEN
302 TRY(FIRST_X_ASSUM(fun th -> MP_TAC(SPEC `x:A` th) THEN
303 ASM_REWRITE_TAC[] THEN ASSUME_TAC th)) THEN
306 (* ------------------------------------------------------------------------- *)
307 (* Totality (cardinal comparability). *)
308 (* ------------------------------------------------------------------------- *)
310 let CARD_LE_TOTAL = prove
311 (`!s:A->bool t:B->bool. s <=_c t \/ t <=_c s`,
314 `P = \R. (!x:A y:B. R(x,y) ==> x IN s /\ y IN t) /\
315 (!x y y'. R(x,y) /\ R(x,y') ==> (y = y')) /\
316 (!x x' y. R(x,y) /\ R(x',y) ==> (x = x'))` THEN
317 MP_TAC(ISPEC `P:((A#B)->bool)->bool` ZL_SUBSETS_UNIONS) THEN ANTS_TAC THENL
318 [GEN_TAC THEN EXPAND_TAC "P" THEN
319 REWRITE_TAC[UNIONS; IN_ELIM_THM] THEN
320 REWRITE_TAC[SUBSET; IN] THEN MESON_TAC[];
322 FIRST_X_ASSUM(SUBST1_TAC o SYM) THEN REWRITE_TAC[] THEN
323 DISCH_THEN(X_CHOOSE_THEN `R:A#B->bool` STRIP_ASSUME_TAC) THEN
324 ASM_CASES_TAC `(!x:A. x IN s ==> ?y:B. y IN t /\ R(x,y)) \/
325 (!y:B. y IN t ==> ?x:A. x IN s /\ R(x,y))`
327 [FIRST_X_ASSUM(K ALL_TAC o SPEC `\(x:A,y:B). T`) THEN
328 FIRST_X_ASSUM(DISJ_CASES_THEN MP_TAC) THEN
329 REWRITE_TAC[RIGHT_IMP_EXISTS_THM; SKOLEM_THM; le_c] THEN ASM_MESON_TAC[];
330 FIRST_X_ASSUM(MP_TAC o GEN_REWRITE_RULE I [DE_MORGAN_THM]) THEN
331 REWRITE_TAC[NOT_FORALL_THM; NOT_IMP] THEN
332 DISCH_THEN(CONJUNCTS_THEN2 (X_CHOOSE_TAC `a:A`) (X_CHOOSE_TAC `b:B`)) THEN
333 FIRST_X_ASSUM(MP_TAC o SPEC
334 `\(x:A,y:B). (x = a) /\ (y = b) \/ R(x,y)`) THEN
335 REWRITE_TAC[SUBSET; FORALL_PAIR_THM; IN; EXTENSION] THEN
336 CONV_TAC(ONCE_DEPTH_CONV GEN_BETA_CONV) THEN
337 RULE_ASSUM_TAC(REWRITE_RULE[IN]) THEN ASM_MESON_TAC[]]);;
339 (* ------------------------------------------------------------------------- *)
340 (* Other variants like "trichotomy of cardinals" now follow easily. *)
341 (* ------------------------------------------------------------------------- *)
343 let CARD_LET_TOTAL = prove
344 (`!s:A->bool t:B->bool. s <=_c t \/ t <_c s`,
345 REWRITE_TAC[lt_c] THEN MESON_TAC[CARD_LE_TOTAL]);;
347 let CARD_LTE_TOTAL = prove
348 (`!s:A->bool t:B->bool. s <_c t \/ t <=_c s`,
349 REWRITE_TAC[lt_c] THEN MESON_TAC[CARD_LE_TOTAL]);;
351 let CARD_LT_TOTAL = prove
352 (`!s:A->bool t:B->bool. s =_c t \/ s <_c t \/ t <_c s`,
353 REWRITE_TAC[lt_c; GSYM CARD_LE_ANTISYM] THEN MESON_TAC[CARD_LE_TOTAL]);;
355 let CARD_NOT_LE = prove
356 (`!s:A->bool t:B->bool. ~(s <=_c t) <=> t <_c s`,
357 REWRITE_TAC[lt_c] THEN MESON_TAC[CARD_LE_TOTAL]);;
359 let CARD_NOT_LT = prove
360 (`!s:A->bool t:B->bool. ~(s <_c t) <=> t <=_c s`,
361 REWRITE_TAC[lt_c] THEN MESON_TAC[CARD_LE_TOTAL]);;
363 let CARD_LT_LE = prove
364 (`!s t. s <_c t <=> s <=_c t /\ ~(s =_c t)`,
365 REWRITE_TAC[lt_c; GSYM CARD_LE_ANTISYM] THEN CONV_TAC TAUT);;
367 let CARD_LE_LT = prove
368 (`!s t. s <=_c t <=> s <_c t \/ s =_c t`,
369 REPEAT GEN_TAC THEN REWRITE_TAC[GSYM CARD_NOT_LT] THEN
370 GEN_REWRITE_TAC (LAND_CONV o RAND_CONV) [CARD_LT_LE] THEN
371 REWRITE_TAC[DE_MORGAN_THM; CARD_NOT_LE; CARD_EQ_SYM]);;
373 let CARD_LE_CONG = prove
374 (`!s:A->bool s':B->bool t:C->bool t':D->bool.
375 s =_c s' /\ t =_c t' ==> (s <=_c t <=> s' <=_c t')`,
376 REPEAT GEN_TAC THEN REWRITE_TAC[GSYM CARD_LE_ANTISYM] THEN
378 `!x y. (b /\ e ==> x) /\ (x /\ c ==> f) /\ (a /\ f ==> y) /\ (y /\ d ==> e)
379 ==> (a /\ b) /\ (c /\ d) ==> (e <=> f)`) THEN
381 [`(s':B->bool) <=_c (t:C->bool)`;
382 `(s:A->bool) <=_c (t':D->bool)`] THEN
383 REWRITE_TAC[CARD_LE_TRANS]);;
385 let CARD_LT_CONG = prove
386 (`!s:A->bool s':B->bool t:C->bool t':D->bool.
387 s =_c s' /\ t =_c t' ==> (s <_c t <=> s' <_c t')`,
388 REPEAT STRIP_TAC THEN REWRITE_TAC[GSYM CARD_NOT_LE] THEN
389 AP_TERM_TAC THEN MATCH_MP_TAC CARD_LE_CONG THEN
392 let CARD_EQ_TRANS = prove
393 (`!s:A->bool t:B->bool u:C->bool.
394 s =_c t /\ t =_c u ==> s =_c u`,
395 REPEAT GEN_TAC THEN REWRITE_TAC[GSYM CARD_LE_ANTISYM] THEN
396 REPEAT STRIP_TAC THEN ASM_MESON_TAC[CARD_LE_TRANS]);;
398 let CARD_EQ_CONG = prove
399 (`!s:A->bool s':B->bool t:C->bool t':D->bool.
400 s =_c s' /\ t =_c t' ==> (s =_c t <=> s' =_c t')`,
401 REPEAT STRIP_TAC THEN EQ_TAC THEN DISCH_TAC THENL
402 [TRANS_CHAIN_TAC CARD_EQ_TRANS [`t:C->bool`; `s:A->bool`];
403 TRANS_CHAIN_TAC CARD_EQ_TRANS [`s':B->bool`; `t':D->bool`]] THEN
404 ASM_MESON_TAC[CARD_EQ_SYM]);;
406 (* ------------------------------------------------------------------------- *)
407 (* Finiteness and infiniteness in terms of cardinality of N. *)
408 (* ------------------------------------------------------------------------- *)
410 let INFINITE_CARD_LE = prove
411 (`!s:A->bool. INFINITE s <=> (UNIV:num->bool) <=_c s`,
412 REPEAT STRIP_TAC THEN EQ_TAC THENL
414 ONCE_REWRITE_TAC[GSYM CONTRAPOS_THM] THEN
415 REWRITE_TAC[INFINITE; le_c; IN_UNIV] THEN REPEAT STRIP_TAC THEN
416 FIRST_ASSUM(MP_TAC o MATCH_MP INFINITE_IMAGE_INJ) THEN
417 DISCH_THEN(MP_TAC o C MATCH_MP num_INFINITE) THEN
418 REWRITE_TAC[INFINITE] THEN
419 MATCH_MP_TAC FINITE_SUBSET THEN EXISTS_TAC `s:A->bool` THEN
420 ASM_SIMP_TAC[SUBSET; IN_IMAGE; IN_UNIV; LEFT_IMP_EXISTS_THM]] THEN
422 SUBGOAL_THEN `?f:num->A. !n. f(n) = @x. x IN (s DIFF IMAGE f {m | m < n})`
424 [MATCH_MP_TAC(MATCH_MP WF_REC WF_num) THEN
425 REWRITE_TAC[IN_IMAGE; IN_ELIM_THM; IN_DIFF] THEN REPEAT STRIP_TAC THEN
426 AP_TERM_TAC THEN ABS_TAC THEN ASM_MESON_TAC[];
428 REWRITE_TAC[le_c] THEN MATCH_MP_TAC MONO_EXISTS THEN
429 X_GEN_TAC `f:num->A` THEN REWRITE_TAC[IN_UNIV] THEN DISCH_TAC THEN
430 SUBGOAL_THEN `!n. (f:num->A)(n) IN (s DIFF IMAGE f {m | m < n})` MP_TAC THENL
431 [GEN_TAC THEN ONCE_ASM_REWRITE_TAC[] THEN CONV_TAC SELECT_CONV THEN
432 REWRITE_TAC[MEMBER_NOT_EMPTY] THEN
433 MATCH_MP_TAC INFINITE_NONEMPTY THEN MATCH_MP_TAC INFINITE_DIFF_FINITE THEN
434 ASM_SIMP_TAC[FINITE_IMAGE; FINITE_NUMSEG_LT];
436 REWRITE_TAC[IN_IMAGE; IN_ELIM_THM; IN_DIFF] THEN MESON_TAC[LT_CASES]);;
438 let FINITE_CARD_LT = prove
439 (`!s:A->bool. FINITE s <=> s <_c (UNIV:num->bool)`,
440 ONCE_REWRITE_TAC[TAUT `(a <=> b) <=> (~a <=> ~b)`] THEN
441 REWRITE_TAC[GSYM INFINITE; CARD_NOT_LT; INFINITE_CARD_LE]);;
443 let CARD_LE_SUBSET = prove
444 (`!s:A->bool t. s SUBSET t ==> s <=_c t`,
445 REWRITE_TAC[SUBSET; le_c] THEN MESON_TAC[I_THM]);;
447 let CARD_LE_UNIV = prove
448 (`!s:A->bool. s <=_c (:A)`,
449 GEN_TAC THEN MATCH_MP_TAC CARD_LE_SUBSET THEN REWRITE_TAC[SUBSET_UNIV]);;
451 let CARD_LE_EQ_SUBSET = prove
452 (`!s:A->bool t:B->bool. s <=_c t <=> ?u. u SUBSET t /\ (s =_c u)`,
453 REPEAT GEN_TAC THEN EQ_TAC THENL
455 REPEAT STRIP_TAC THEN
456 FIRST_ASSUM(MP_TAC o MATCH_MP CARD_LE_SUBSET) THEN
457 MATCH_MP_TAC(TAUT `(a <=> b) ==> b ==> a`) THEN
458 MATCH_MP_TAC CARD_LE_CONG THEN
459 ASM_REWRITE_TAC[CARD_LE_CONG; CARD_EQ_REFL]] THEN
460 REWRITE_TAC[le_c; eq_c] THEN
461 DISCH_THEN(X_CHOOSE_THEN `f:A->B` STRIP_ASSUME_TAC) THEN
462 REWRITE_TAC[RIGHT_AND_EXISTS_THM] THEN EXISTS_TAC `IMAGE (f:A->B) s` THEN
463 EXISTS_TAC `f:A->B` THEN REWRITE_TAC[IN_IMAGE; SUBSET] THEN
466 let CARD_INFINITE_CONG = prove
467 (`!s:A->bool t:B->bool. s =_c t ==> (INFINITE s <=> INFINITE t)`,
468 REWRITE_TAC[INFINITE_CARD_LE] THEN REPEAT STRIP_TAC THEN
469 MATCH_MP_TAC CARD_LE_CONG THEN ASM_REWRITE_TAC[CARD_EQ_REFL]);;
471 let CARD_FINITE_CONG = prove
472 (`!s:A->bool t:B->bool. s =_c t ==> (FINITE s <=> FINITE t)`,
473 ONCE_REWRITE_TAC[TAUT `(a <=> b) <=> (~a <=> ~b)`] THEN
474 REWRITE_TAC[GSYM INFINITE; CARD_INFINITE_CONG]);;
476 let CARD_LE_FINITE = prove
477 (`!s:A->bool t:B->bool. FINITE t /\ s <=_c t ==> FINITE s`,
478 ASM_MESON_TAC[CARD_LE_EQ_SUBSET; FINITE_SUBSET; CARD_FINITE_CONG]);;
480 let CARD_EQ_FINITE = prove
481 (`!s t:A->bool. FINITE t /\ s =_c t ==> FINITE s`,
482 REWRITE_TAC[GSYM CARD_LE_ANTISYM] THEN MESON_TAC[CARD_LE_FINITE]);;
484 let CARD_LE_INFINITE = prove
485 (`!s:A->bool t:B->bool. INFINITE s /\ s <=_c t ==> INFINITE t`,
486 MESON_TAC[CARD_LE_FINITE; INFINITE]);;
488 let CARD_LT_FINITE_INFINITE = prove
489 (`!s:A->bool t:B->bool. FINITE s /\ INFINITE t ==> s <_c t`,
490 REWRITE_TAC[GSYM CARD_NOT_LE; INFINITE] THEN MESON_TAC[CARD_LE_FINITE]);;
492 let CARD_LE_CARD_IMP = prove
493 (`!s:A->bool t:B->bool. FINITE t /\ s <=_c t ==> CARD s <= CARD t`,
494 REPEAT STRIP_TAC THEN
495 SUBGOAL_THEN `FINITE(s:A->bool)` ASSUME_TAC THENL
496 [ASM_MESON_TAC[CARD_LE_FINITE]; ALL_TAC] THEN
497 FIRST_X_ASSUM(MP_TAC o GEN_REWRITE_RULE I [le_c]) THEN
498 DISCH_THEN(X_CHOOSE_THEN `f:A->B` STRIP_ASSUME_TAC) THEN
499 MATCH_MP_TAC LE_TRANS THEN EXISTS_TAC `CARD(IMAGE (f:A->B) s)` THEN
501 [MATCH_MP_TAC(ARITH_RULE `(m = n:num) ==> n <= m`) THEN
502 MATCH_MP_TAC CARD_IMAGE_INJ THEN ASM_REWRITE_TAC[];
503 MATCH_MP_TAC CARD_SUBSET THEN ASM_REWRITE_TAC[] THEN
504 ASM_MESON_TAC[SUBSET; IN_IMAGE]]);;
506 let CARD_EQ_CARD_IMP = prove
507 (`!s:A->bool t:B->bool. FINITE t /\ s =_c t ==> (CARD s = CARD t)`,
508 MESON_TAC[CARD_FINITE_CONG; LE_ANTISYM; CARD_LE_ANTISYM; CARD_LE_CARD_IMP]);;
510 let CARD_LE_CARD = prove
511 (`!s:A->bool t:B->bool.
512 FINITE s /\ FINITE t ==> (s <=_c t <=> CARD s <= CARD t)`,
513 REPEAT STRIP_TAC THEN
514 MATCH_MP_TAC(TAUT `(a ==> b) /\ (~a ==> ~b) ==> (a <=> b)`) THEN
515 ASM_SIMP_TAC[CARD_LE_CARD_IMP] THEN
516 REWRITE_TAC[CARD_NOT_LE; NOT_LE] THEN REWRITE_TAC[lt_c; LT_LE] THEN
517 ASM_SIMP_TAC[CARD_LE_CARD_IMP] THEN
518 MATCH_MP_TAC(TAUT `(c ==> a ==> b) ==> a /\ ~b ==> ~c`) THEN
519 DISCH_TAC THEN GEN_REWRITE_TAC LAND_CONV [CARD_LE_EQ_SUBSET] THEN
520 DISCH_THEN(X_CHOOSE_THEN `u:A->bool` STRIP_ASSUME_TAC) THEN
521 MATCH_MP_TAC CARD_EQ_IMP_LE THEN
522 SUBGOAL_THEN `u:A->bool = s` (fun th -> ASM_MESON_TAC[th; CARD_EQ_SYM]) THEN
523 ASM_MESON_TAC[CARD_SUBSET_EQ; CARD_EQ_CARD_IMP; CARD_EQ_SYM]);;
525 let CARD_EQ_CARD = prove
526 (`!s:A->bool t:B->bool.
527 FINITE s /\ FINITE t ==> (s =_c t <=> (CARD s = CARD t))`,
528 MESON_TAC[CARD_FINITE_CONG; LE_ANTISYM; CARD_LE_ANTISYM; CARD_LE_CARD]);;
530 let CARD_LT_CARD = prove
531 (`!s:A->bool t:B->bool.
532 FINITE s /\ FINITE t ==> (s <_c t <=> CARD s < CARD t)`,
533 SIMP_TAC[CARD_LE_CARD; GSYM NOT_LE; GSYM CARD_NOT_LE]);;
535 let CARD_HAS_SIZE_CONG = prove
536 (`!s:A->bool t:B->bool n. s HAS_SIZE n /\ s =_c t ==> t HAS_SIZE n`,
537 REWRITE_TAC[HAS_SIZE] THEN
538 MESON_TAC[CARD_EQ_CARD; CARD_FINITE_CONG]);;
540 let CARD_LE_IMAGE = prove
541 (`!f s. IMAGE f s <=_c s`,
542 REWRITE_TAC[LE_C; FORALL_IN_IMAGE] THEN MESON_TAC[]);;
544 let CARD_LE_IMAGE_GEN = prove
545 (`!f:A->B s t. t SUBSET IMAGE f s ==> t <=_c s`,
546 REPEAT STRIP_TAC THEN TRANS_TAC CARD_LE_TRANS `IMAGE (f:A->B) s` THEN
547 ASM_SIMP_TAC[CARD_LE_IMAGE; CARD_LE_SUBSET]);;
549 let CARD_EQ_IMAGE = prove
551 (!x y. x IN s /\ y IN s /\ f x = f y ==> x = y)
552 ==> IMAGE f s =_c s`,
553 REPEAT STRIP_TAC THEN ONCE_REWRITE_TAC[CARD_EQ_SYM] THEN
554 REWRITE_TAC[eq_c] THEN EXISTS_TAC `f:A->B` THEN ASM SET_TAC[]);;
556 (* ------------------------------------------------------------------------- *)
557 (* Cardinal arithmetic operations. *)
558 (* ------------------------------------------------------------------------- *)
560 parse_as_infix("+_c",(16,"right"));;
561 parse_as_infix("*_c",(20,"right"));;
563 let add_c = new_definition
564 `s +_c t = {INL x | x IN s} UNION {INR y | y IN t}`;;
566 let mul_c = new_definition
567 `s *_c t = {(x,y) | x IN s /\ y IN t}`;;
569 (* ------------------------------------------------------------------------- *)
570 (* Congruence properties for the arithmetic operators. *)
571 (* ------------------------------------------------------------------------- *)
573 let CARD_LE_ADD = prove
574 (`!s:A->bool s':B->bool t:C->bool t':D->bool.
575 s <=_c s' /\ t <=_c t' ==> s +_c t <=_c s' +_c t'`,
576 REPEAT GEN_TAC THEN REWRITE_TAC[le_c; add_c] THEN
577 DISCH_THEN(CONJUNCTS_THEN2
578 (X_CHOOSE_THEN `f:A->B` STRIP_ASSUME_TAC)
579 (X_CHOOSE_THEN `g:C->D` STRIP_ASSUME_TAC)) THEN
580 MP_TAC(prove_recursive_functions_exist sum_RECURSION
581 `(!x. h(INL x) = INL((f:A->B) x)) /\ (!y. h(INR y) = INR((g:C->D) y))`) THEN
582 MATCH_MP_TAC MONO_EXISTS THEN X_GEN_TAC `h:(A+C)->(B+D)` THEN STRIP_TAC THEN
583 REWRITE_TAC[IN_UNION; IN_ELIM_THM] THEN
584 CONJ_TAC THEN REPEAT GEN_TAC THEN
585 REPEAT(DISCH_THEN(CONJUNCTS_THEN2 STRIP_ASSUME_TAC MP_TAC) THEN
586 ASM_REWRITE_TAC[]) THEN
587 ASM_REWRITE_TAC[sum_DISTINCT;
591 let CARD_LE_MUL = prove
592 (`!s:A->bool s':B->bool t:C->bool t':D->bool.
593 s <=_c s' /\ t <=_c t' ==> s *_c t <=_c s' *_c t'`,
594 REPEAT GEN_TAC THEN REWRITE_TAC[le_c; mul_c] THEN
595 DISCH_THEN(CONJUNCTS_THEN2
596 (X_CHOOSE_THEN `f:A->B` STRIP_ASSUME_TAC)
597 (X_CHOOSE_THEN `g:C->D` STRIP_ASSUME_TAC)) THEN
598 EXISTS_TAC `\(x,y). (f:A->B) x,(g:C->D) y` THEN
599 REWRITE_TAC[FORALL_PAIR_THM; IN_ELIM_THM] THEN
600 CONV_TAC(ONCE_DEPTH_CONV GEN_BETA_CONV) THEN
601 REWRITE_TAC[PAIR_EQ] THEN ASM_MESON_TAC[]);;
603 let CARD_FUNSPACE_LE = prove
604 (`(:A) <=_c (:A') /\ (:B) <=_c (:B') ==> (:A->B) <=_c (:A'->B')`,
605 REWRITE_TAC[le_c; IN_UNIV] THEN DISCH_THEN(CONJUNCTS_THEN2
606 (X_CHOOSE_TAC `f:A->A'`) (X_CHOOSE_TAC `g:B->B'`)) THEN
607 SUBGOAL_THEN `?f':A'->A. !x. f'(f x) = x` STRIP_ASSUME_TAC THENL
608 [ASM_REWRITE_TAC[GSYM INJECTIVE_LEFT_INVERSE]; ALL_TAC] THEN
609 EXISTS_TAC `\h. (g:B->B') o (h:A->B) o (f':A'->A)` THEN
610 ASM_REWRITE_TAC[o_DEF; FUN_EQ_THM] THEN ASM_MESON_TAC[]);;
612 let CARD_ADD_CONG = prove
613 (`!s:A->bool s':B->bool t:C->bool t':D->bool.
614 s =_c s' /\ t =_c t' ==> s +_c t =_c s' +_c t'`,
615 SIMP_TAC[CARD_LE_ADD; GSYM CARD_LE_ANTISYM]);;
617 let CARD_MUL_CONG = prove
618 (`!s:A->bool s':B->bool t:C->bool t':D->bool.
619 s =_c s' /\ t =_c t' ==> s *_c t =_c s' *_c t'`,
620 SIMP_TAC[CARD_LE_MUL; GSYM CARD_LE_ANTISYM]);;
622 let CARD_FUNSPACE_CONG = prove
623 (`(:A) =_c (:A') /\ (:B) =_c (:B') ==> (:A->B) =_c (:A'->B')`,
624 SIMP_TAC[GSYM CARD_LE_ANTISYM; CARD_FUNSPACE_LE]);;
626 (* ------------------------------------------------------------------------- *)
628 (* ------------------------------------------------------------------------- *)
630 let MUL_C_UNIV = prove
631 (`(:A) *_c (:B) = (:A#B)`,
632 REWRITE_TAC[EXTENSION; FORALL_PAIR_THM; mul_c; IN_ELIM_PAIR_THM; IN_UNIV]);;
634 let CARD_FUNSPACE_CURRY = prove
635 (`(:A->B->C) =_c (:A#B->C)`,
636 REWRITE_TAC[EQ_C_BIJECTIONS] THEN
637 EXISTS_TAC `\(f:A->B->C) (x,y). f x y` THEN
638 EXISTS_TAC `\(g:A#B->C) x y. g(x,y)` THEN
639 REWRITE_TAC[IN_UNIV] THEN
640 REWRITE_TAC[FUN_EQ_THM; FORALL_PAIR_THM]);;
642 let IN_CARD_ADD = prove
643 (`(!x. INL(x) IN (s +_c t) <=> x IN s) /\
644 (!y. INR(y) IN (s +_c t) <=> y IN t)`,
645 REWRITE_TAC[add_c; IN_UNION; IN_ELIM_THM] THEN
646 REWRITE_TAC[sum_DISTINCT; sum_INJECTIVE] THEN MESON_TAC[]);;
648 let IN_CARD_MUL = prove
649 (`!s t x y. (x,y) IN (s *_c t) <=> x IN s /\ y IN t`,
650 REWRITE_TAC[mul_c; IN_ELIM_THM; PAIR_EQ] THEN MESON_TAC[]);;
652 let CARD_LE_SQUARE = prove
653 (`!s:A->bool. s <=_c s *_c s`,
654 GEN_TAC THEN REWRITE_TAC[le_c] THEN EXISTS_TAC `\x:A. x,(@z:A. z IN s)` THEN
655 SIMP_TAC[IN_CARD_MUL; PAIR_EQ] THEN
656 CONV_TAC(ONCE_DEPTH_CONV SELECT_CONV) THEN MESON_TAC[]);;
658 let CARD_SQUARE_NUM = prove
659 (`(UNIV:num->bool) *_c (UNIV:num->bool) =_c (UNIV:num->bool)`,
660 REWRITE_TAC[GSYM CARD_LE_ANTISYM; CARD_LE_SQUARE] THEN
661 REWRITE_TAC[le_c; IN_UNIV; mul_c; IN_ELIM_THM] THEN
662 EXISTS_TAC `\(x,y). NUMPAIR x y` THEN
663 REWRITE_TAC[FORALL_PAIR_THM] THEN
664 CONV_TAC(ONCE_DEPTH_CONV GEN_BETA_CONV) THEN MESON_TAC[NUMPAIR_INJ]);;
666 let UNION_LE_ADD_C = prove
667 (`!s t:A->bool. (s UNION t) <=_c s +_c t`,
668 REPEAT GEN_TAC THEN MATCH_MP_TAC CARD_LE_IMAGE_GEN THEN
669 EXISTS_TAC `function INL x -> (x:A) | INR x -> x` THEN
670 REWRITE_TAC[add_c; IMAGE_UNION] THEN ONCE_REWRITE_TAC[SIMPLE_IMAGE] THEN
671 REWRITE_TAC[GSYM IMAGE_o; o_DEF] THEN SET_TAC[]);;
673 let CARD_ADD_C = prove
674 (`!s t. FINITE s /\ FINITE t ==> CARD(s +_c t) = CARD s + CARD t`,
675 REPEAT STRIP_TAC THEN REWRITE_TAC[add_c] THEN
676 W(MP_TAC o PART_MATCH (lhs o rand) CARD_UNION o lhand o snd) THEN
677 ASM_SIMP_TAC[SIMPLE_IMAGE; FINITE_IMAGE] THEN
678 REWRITE_TAC[SET_RULE `IMAGE f s INTER IMAGE g t = {} <=>
679 !x y. x IN s /\ y IN t ==> ~(f x = g y)`] THEN
680 REWRITE_TAC[sum_DISTINCT] THEN DISCH_THEN SUBST1_TAC THEN
681 BINOP_TAC THEN MATCH_MP_TAC CARD_IMAGE_INJ THEN
682 ASM_SIMP_TAC[sum_INJECTIVE]);;
684 (* ------------------------------------------------------------------------- *)
685 (* Various "arithmetical" lemmas. *)
686 (* ------------------------------------------------------------------------- *)
688 let CARD_ADD_SYM = prove
689 (`!s:A->bool t:B->bool. s +_c t =_c t +_c s`,
690 REPEAT GEN_TAC THEN REWRITE_TAC[eq_c] THEN
691 MP_TAC(prove_recursive_functions_exist sum_RECURSION
692 `(!x. (h:A+B->B+A) (INL x) = INR x) /\ (!y. h(INR y) = INL y)`) THEN
693 MATCH_MP_TAC MONO_EXISTS THEN
694 SIMP_TAC[FORALL_SUM_THM; EXISTS_SUM_THM; EXISTS_UNIQUE_THM] THEN
695 REWRITE_TAC[sum_DISTINCT; sum_INJECTIVE; IN_CARD_ADD] THEN MESON_TAC[]);;
697 let CARD_ADD_ASSOC = prove
698 (`!s:A->bool t:B->bool u:C->bool. s +_c (t +_c u) =_c (s +_c t) +_c u`,
699 REPEAT GEN_TAC THEN REWRITE_TAC[eq_c] THEN
700 CHOOSE_TAC(prove_recursive_functions_exist sum_RECURSION
701 `(!u. (i:B+C->(A+B)+C) (INL u) = INL(INR u)) /\
702 (!v. i(INR v) = INR v)`) THEN
703 MP_TAC(prove_recursive_functions_exist sum_RECURSION
704 `(!x. (h:A+B+C->(A+B)+C) (INL x) = INL(INL x)) /\
705 (!z. h(INR z) = i(z))`) THEN
706 MATCH_MP_TAC MONO_EXISTS THEN GEN_TAC THEN STRIP_TAC THEN
707 ASM_REWRITE_TAC[FORALL_SUM_THM; EXISTS_SUM_THM; EXISTS_UNIQUE_THM;
708 sum_DISTINCT; sum_INJECTIVE; IN_CARD_ADD] THEN
711 let CARD_MUL_SYM = prove
712 (`!s:A->bool t:B->bool. s *_c t =_c t *_c s`,
713 REPEAT GEN_TAC THEN REWRITE_TAC[eq_c] THEN
714 MP_TAC(prove_recursive_functions_exist pair_RECURSION
715 `(!x:A y:B. h(x,y) = (y,x))`) THEN
716 MATCH_MP_TAC MONO_EXISTS THEN GEN_TAC THEN STRIP_TAC THEN
717 REWRITE_TAC[EXISTS_UNIQUE_THM; FORALL_PAIR_THM; EXISTS_PAIR_THM] THEN
718 ASM_REWRITE_TAC[FORALL_PAIR_THM; IN_CARD_MUL; PAIR_EQ] THEN
721 let CARD_MUL_ASSOC = prove
722 (`!s:A->bool t:B->bool u:C->bool. s *_c (t *_c u) =_c (s *_c t) *_c u`,
723 REPEAT GEN_TAC THEN REWRITE_TAC[eq_c] THEN
724 CHOOSE_TAC(prove_recursive_functions_exist pair_RECURSION
725 `(!x y z. (i:A->B#C->(A#B)#C) x (y,z) = (x,y),z)`) THEN
726 MP_TAC(prove_recursive_functions_exist pair_RECURSION
727 `(!x p. (h:A#B#C->(A#B)#C) (x,p) = i x p)`) THEN
728 MATCH_MP_TAC MONO_EXISTS THEN GEN_TAC THEN STRIP_TAC THEN
729 REWRITE_TAC[EXISTS_UNIQUE_THM; FORALL_PAIR_THM; EXISTS_PAIR_THM] THEN
730 ASM_REWRITE_TAC[FORALL_PAIR_THM; IN_CARD_MUL; PAIR_EQ] THEN
733 let CARD_LDISTRIB = prove
734 (`!s:A->bool t:B->bool u:C->bool.
735 s *_c (t +_c u) =_c (s *_c t) +_c (s *_c u)`,
736 REPEAT GEN_TAC THEN REWRITE_TAC[eq_c] THEN
737 CHOOSE_TAC(prove_recursive_functions_exist sum_RECURSION
738 `(!x y. (i:A->(B+C)->A#B+A#C) x (INL y) = INL(x,y)) /\
739 (!x z. (i:A->(B+C)->A#B+A#C) x (INR z) = INR(x,z))`) THEN
740 MP_TAC(prove_recursive_functions_exist pair_RECURSION
741 `(!x s. (h:A#(B+C)->(A#B)+(A#C)) (x,s) = i x s)`) THEN
742 MATCH_MP_TAC MONO_EXISTS THEN GEN_TAC THEN STRIP_TAC THEN
743 ASM_REWRITE_TAC[EXISTS_UNIQUE_THM; FORALL_PAIR_THM; EXISTS_PAIR_THM;
744 FORALL_SUM_THM; EXISTS_SUM_THM; PAIR_EQ; IN_CARD_MUL;
745 sum_DISTINCT; sum_INJECTIVE; IN_CARD_ADD] THEN
748 let CARD_RDISTRIB = prove
749 (`!s:A->bool t:B->bool u:C->bool.
750 (s +_c t) *_c u =_c (s *_c u) +_c (t *_c u)`,
752 TRANS_TAC CARD_EQ_TRANS
753 `(u:C->bool) *_c ((s:A->bool) +_c (t:B->bool))` THEN
754 REWRITE_TAC[CARD_MUL_SYM] THEN
755 TRANS_TAC CARD_EQ_TRANS
756 `(u:C->bool) *_c (s:A->bool) +_c (u:C->bool) *_c (t:B->bool)` THEN
757 REWRITE_TAC[CARD_LDISTRIB] THEN
758 MATCH_MP_TAC CARD_ADD_CONG THEN REWRITE_TAC[CARD_MUL_SYM]);;
760 let CARD_LE_ADDR = prove
761 (`!s:A->bool t:B->bool. s <=_c s +_c t`,
762 REPEAT GEN_TAC THEN REWRITE_TAC[le_c] THEN
763 EXISTS_TAC `INL:A->A+B` THEN SIMP_TAC[IN_CARD_ADD; sum_INJECTIVE]);;
765 let CARD_LE_ADDL = prove
766 (`!s:A->bool t:B->bool. t <=_c s +_c t`,
767 REPEAT GEN_TAC THEN REWRITE_TAC[le_c] THEN
768 EXISTS_TAC `INR:B->A+B` THEN SIMP_TAC[IN_CARD_ADD; sum_INJECTIVE]);;
770 (* ------------------------------------------------------------------------- *)
771 (* A rather special lemma but temporarily useful. *)
772 (* ------------------------------------------------------------------------- *)
774 let CARD_ADD_LE_MUL_INFINITE = prove
775 (`!s:A->bool. INFINITE s ==> s +_c s <=_c s *_c s`,
776 GEN_TAC THEN REWRITE_TAC[INFINITE_CARD_LE; le_c; IN_UNIV] THEN
777 DISCH_THEN(X_CHOOSE_THEN `f:num->A` STRIP_ASSUME_TAC) THEN
778 MP_TAC(prove_recursive_functions_exist sum_RECURSION
779 `(!x. h(INL x) = (f(0),x):A#A) /\ (!x. h(INR x) = (f(1),x))`) THEN
780 MATCH_MP_TAC MONO_EXISTS THEN X_GEN_TAC `h:A+A->A#A` THEN
782 REPEAT((MATCH_MP_TAC sum_INDUCT THEN
783 ASM_REWRITE_TAC[IN_CARD_ADD; IN_CARD_MUL; PAIR_EQ])
784 ORELSE STRIP_TAC) THEN
785 ASM_REWRITE_TAC[] THEN ASM_MESON_TAC[NUM_REDUCE_CONV `1 = 0`]);;
787 (* ------------------------------------------------------------------------- *)
788 (* Relate cardinal addition to the simple union operation. *)
789 (* ------------------------------------------------------------------------- *)
791 let CARD_DISJOINT_UNION = prove
792 (`!s:A->bool t. (s INTER t = {}) ==> (s UNION t =_c s +_c t)`,
793 REPEAT GEN_TAC THEN REWRITE_TAC[EXTENSION; IN_INTER; NOT_IN_EMPTY] THEN
794 STRIP_TAC THEN REWRITE_TAC[eq_c; IN_UNION] THEN
795 EXISTS_TAC `\x:A. if x IN s then INL x else INR x` THEN
796 REWRITE_TAC[FORALL_SUM_THM; IN_CARD_ADD] THEN
797 REWRITE_TAC[COND_RAND; COND_RATOR] THEN
798 REWRITE_TAC[TAUT `(if b then x else y) <=> b /\ x \/ ~b /\ y`] THEN
799 REWRITE_TAC[sum_DISTINCT; sum_INJECTIVE; IN_CARD_ADD] THEN
802 (* ------------------------------------------------------------------------- *)
803 (* The key to arithmetic on infinite cardinals: k^2 = k. *)
804 (* ------------------------------------------------------------------------- *)
806 let CARD_SQUARE_INFINITE = prove
807 (`!k:A->bool. INFINITE k ==> (k *_c k =_c k)`,
809 (`INFINITE(s:A->bool) /\ s SUBSET k /\
810 (!x y. R(x,y) ==> x IN (s *_c s) /\ y IN s) /\
811 (!x. x IN (s *_c s) ==> ?!y. y IN s /\ R(x,y)) /\
812 (!y:A. y IN s ==> ?!x. x IN (s *_c s) /\ R(x,y))
813 ==> (s = {z | ?p. R(p,z)})`,
814 REWRITE_TAC[EXTENSION; IN_ELIM_THM] THEN MESON_TAC[]) in
815 REPEAT STRIP_TAC THEN
817 `P = \R. ?s. INFINITE(s:A->bool) /\ s SUBSET k /\
818 (!x y. R(x,y) ==> x IN (s *_c s) /\ y IN s) /\
819 (!x. x IN (s *_c s) ==> ?!y. y IN s /\ R(x,y)) /\
820 (!y. y IN s ==> ?!x. x IN (s *_c s) /\ R(x,y))` THEN
821 MP_TAC(ISPEC `P:((A#A)#A->bool)->bool` ZL_SUBSETS_UNIONS_NONEMPTY) THEN
824 [FIRST_X_ASSUM(SUBST1_TAC o SYM) THEN REWRITE_TAC[] THEN
825 ONCE_REWRITE_TAC[SWAP_EXISTS_THM] THEN
826 REWRITE_TAC[RIGHT_EXISTS_AND_THM; GSYM EQ_C] THEN
827 FIRST_X_ASSUM(MP_TAC o GEN_REWRITE_RULE I [INFINITE_CARD_LE]) THEN
828 REWRITE_TAC[CARD_LE_EQ_SUBSET] THEN
829 MATCH_MP_TAC MONO_EXISTS THEN X_GEN_TAC `s:A->bool` THEN
830 STRIP_TAC THEN ASM_REWRITE_TAC[] THEN CONJ_TAC THENL
831 [ASM_MESON_TAC[num_INFINITE; CARD_INFINITE_CONG]; ALL_TAC] THEN
832 FIRST_ASSUM(fun th ->
833 MP_TAC(MATCH_MP CARD_MUL_CONG (CONJ th th))) THEN
834 GEN_REWRITE_TAC LAND_CONV [CARD_EQ_SYM] THEN
835 DISCH_THEN(MP_TAC o C CONJ CARD_SQUARE_NUM) THEN
836 DISCH_THEN(MP_TAC o MATCH_MP CARD_EQ_TRANS) THEN
837 FIRST_ASSUM(fun th ->
838 DISCH_THEN(ACCEPT_TAC o MATCH_MP CARD_EQ_TRANS o C CONJ th));
841 `P = \R. INFINITE {z | ?x y. R((x,y),z)} /\
842 (!x:A y z. R((x,y),z) ==> x IN k /\ y IN k /\ z IN k) /\
843 (!x y. (?u v. R((u,v),x)) /\ (?u v. R((u,v),y))
844 ==> ?z. R((x,y),z)) /\
845 (!x y. (?z. R((x,y),z))
846 ==> (?u v. R((u,v),x)) /\ (?u v. R((u,v),y))) /\
847 (!x y z1 z2. R((x,y),z1) /\ R((x,y),z2) ==> (z1 = z2)) /\
848 (!x1 y1 x2 y2 z. R((x1,y1),z) /\ R((x2,y2),z)
849 ==> (x1 = x2) /\ (y1 = y2))`
851 [FIRST_X_ASSUM(SUBST1_TAC o SYM) THEN REWRITE_TAC[] THEN
852 ONCE_REWRITE_TAC[MATCH_MP(TAUT `(a ==> b) ==> (a <=> b /\ a)`) lemma] THEN
853 REWRITE_TAC[UNWIND_THM2] THEN REWRITE_TAC[FUN_EQ_THM] THEN
854 REWRITE_TAC[IN_CARD_MUL; EXISTS_PAIR_THM; SUBSET; FUN_EQ_THM;
855 IN_ELIM_THM; FORALL_PAIR_THM; EXISTS_UNIQUE_THM;
856 UNIONS; PAIR_EQ] THEN
857 GEN_TAC THEN AP_TERM_TAC THEN MESON_TAC[];
859 FIRST_X_ASSUM(K ALL_TAC o SYM) THEN REWRITE_TAC[] THEN GEN_TAC THEN
860 GEN_REWRITE_TAC (LAND_CONV o ONCE_DEPTH_CONV)
861 [TAUT `a ==> b /\ c <=> (a ==> b) /\ (a ==> c)`] THEN
862 GEN_REWRITE_TAC (LAND_CONV o ONCE_DEPTH_CONV) [FORALL_AND_THM] THEN
864 `(c /\ d ==> f) /\ (a /\ b ==> e)
865 ==> (a /\ (b /\ c) /\ d ==> e /\ f)`) THEN
867 [REWRITE_TAC[UNIONS; IN_ELIM_THM] THEN
868 REWRITE_TAC[SUBSET; IN] THEN MESON_TAC[];
870 DISCH_THEN(CONJUNCTS_THEN2 (X_CHOOSE_TAC `s:(A#A)#A->bool`) MP_TAC) THEN
871 DISCH_THEN(MP_TAC o SPEC `s:(A#A)#A->bool`) THEN
872 ASM_REWRITE_TAC[INFINITE; CONTRAPOS_THM] THEN
873 MATCH_MP_TAC(ONCE_REWRITE_RULE[TAUT `a /\ b ==> c <=> b ==> a ==> c`]
875 REWRITE_TAC[SUBSET; IN_ELIM_THM; UNIONS] THEN ASM_MESON_TAC[IN];
877 FIRST_X_ASSUM(SUBST1_TAC o SYM) THEN REWRITE_TAC[] THEN
878 DISCH_THEN(X_CHOOSE_THEN `R:(A#A)#A->bool`
879 (CONJUNCTS_THEN2 (X_CHOOSE_TAC `s:A->bool`) ASSUME_TAC)) THEN
880 SUBGOAL_THEN `(s:A->bool) *_c s =_c s` ASSUME_TAC THENL
881 [REWRITE_TAC[EQ_C] THEN EXISTS_TAC `R:(A#A)#A->bool` THEN ASM_REWRITE_TAC[];
883 SUBGOAL_THEN `s +_c s <=_c (s:A->bool)` ASSUME_TAC THENL
884 [TRANS_TAC CARD_LE_TRANS `(s:A->bool) *_c s` THEN
885 ASM_SIMP_TAC[CARD_EQ_IMP_LE; CARD_ADD_LE_MUL_INFINITE];
887 SUBGOAL_THEN `(s:A->bool) INTER (k DIFF s) = {}` ASSUME_TAC THENL
888 [REWRITE_TAC[EXTENSION; IN_INTER; IN_DIFF; NOT_IN_EMPTY] THEN MESON_TAC[];
890 DISJ_CASES_TAC(ISPECL [`k DIFF (s:A->bool)`; `s:A->bool`] CARD_LE_TOTAL)
892 [SUBGOAL_THEN `k = (s:A->bool) UNION (k DIFF s)` SUBST1_TAC THENL
893 [FIRST_ASSUM(MP_TAC o CONJUNCT1 o CONJUNCT2) THEN
894 REWRITE_TAC[SUBSET; EXTENSION; IN_INTER; NOT_IN_EMPTY;
895 IN_UNION; IN_DIFF] THEN
898 REWRITE_TAC[GSYM CARD_LE_ANTISYM; CARD_LE_SQUARE] THEN
899 TRANS_TAC CARD_LE_TRANS
900 `((s:A->bool) +_c (k DIFF s:A->bool)) *_c (s +_c k DIFF s)` THEN
901 ASM_SIMP_TAC[CARD_DISJOINT_UNION; CARD_EQ_IMP_LE; CARD_MUL_CONG] THEN
902 TRANS_TAC CARD_LE_TRANS `((s:A->bool) +_c s) *_c (s +_c s)` THEN
903 ASM_SIMP_TAC[CARD_LE_ADD; CARD_LE_MUL; CARD_LE_REFL] THEN
904 TRANS_TAC CARD_LE_TRANS `(s:A->bool) *_c s` THEN
905 ASM_SIMP_TAC[CARD_LE_MUL] THEN
906 TRANS_TAC CARD_LE_TRANS `s:A->bool` THEN ASM_SIMP_TAC[CARD_EQ_IMP_LE] THEN
907 REWRITE_TAC[CARD_LE_EQ_SUBSET] THEN EXISTS_TAC `s:A->bool` THEN
908 SIMP_TAC[CARD_EQ_REFL; SUBSET; IN_UNION];
910 UNDISCH_TAC `s:A->bool <=_c k DIFF s` THEN
911 REWRITE_TAC[CARD_LE_EQ_SUBSET] THEN
912 DISCH_THEN(X_CHOOSE_THEN `d:A->bool` STRIP_ASSUME_TAC) THEN
913 SUBGOAL_THEN `(s:A->bool *_c d) UNION (d *_c s) UNION (d *_c d) =_c d`
915 [TRANS_TAC CARD_EQ_TRANS
916 `((s:A->bool) *_c (d:A->bool)) +_c ((d *_c s) +_c (d *_c d))` THEN
918 [TRANS_TAC CARD_EQ_TRANS
919 `((s:A->bool) *_c d) +_c ((d *_c s) UNION (d *_c d))` THEN
922 MATCH_MP_TAC CARD_ADD_CONG THEN REWRITE_TAC[CARD_EQ_REFL]] THEN
923 MATCH_MP_TAC CARD_DISJOINT_UNION THEN
924 UNDISCH_TAC `s INTER (k DIFF s:A->bool) = {}` THEN
925 UNDISCH_TAC `d SUBSET (k DIFF s:A->bool)` THEN
926 REWRITE_TAC[EXTENSION; SUBSET; FORALL_PAIR_THM; NOT_IN_EMPTY;
927 IN_INTER; IN_UNION; IN_CARD_MUL; IN_DIFF] THEN MESON_TAC[];
929 TRANS_TAC CARD_EQ_TRANS `s:A->bool` THEN ASM_REWRITE_TAC[] THEN
930 TRANS_TAC CARD_EQ_TRANS
931 `(s:A->bool *_c s) +_c (s *_c s) +_c (s *_c s)` THEN
933 [REPEAT(MATCH_MP_TAC CARD_ADD_CONG THEN CONJ_TAC) THEN
934 MATCH_MP_TAC CARD_MUL_CONG THEN ASM_REWRITE_TAC[CARD_EQ_REFL] THEN
935 ONCE_REWRITE_TAC[CARD_EQ_SYM] THEN ASM_REWRITE_TAC[];
937 TRANS_TAC CARD_EQ_TRANS `(s:A->bool) +_c s +_c s` THEN CONJ_TAC THENL
938 [REPEAT(MATCH_MP_TAC CARD_ADD_CONG THEN ASM_REWRITE_TAC[]);
940 REWRITE_TAC[GSYM CARD_LE_ANTISYM; CARD_LE_ADDR] THEN
941 TRANS_TAC CARD_LE_TRANS `(s:A->bool) +_c s` THEN
942 ASM_SIMP_TAC[CARD_LE_ADD; CARD_LE_REFL];
944 FIRST_X_ASSUM(CONJUNCTS_THEN ASSUME_TAC) THEN
945 FIRST_X_ASSUM(CONJUNCTS_THEN ASSUME_TAC) THEN
946 REWRITE_TAC[EQ_C; IN_UNION] THEN
947 DISCH_THEN(X_CHOOSE_TAC `S:(A#A)#A->bool`) THEN
948 FIRST_X_ASSUM(MP_TAC o SPEC `\x:(A#A)#A. R(x) \/ S(x)`) THEN
949 ONCE_REWRITE_TAC[GSYM CONTRAPOS_THM] THEN DISCH_THEN(K ALL_TAC) THEN
950 REWRITE_TAC[NOT_IMP] THEN REPEAT CONJ_TAC THENL
951 [EXISTS_TAC `(s:A->bool) UNION d`;
952 SIMP_TAC[SUBSET; IN];
953 SUBGOAL_THEN `~(d:A->bool = {})` MP_TAC THENL
954 [DISCH_THEN(MP_TAC o AP_TERM `FINITE:(A->bool)->bool`) THEN
955 REWRITE_TAC[FINITE_RULES; GSYM INFINITE] THEN
956 ASM_MESON_TAC[CARD_INFINITE_CONG];
958 REWRITE_TAC[GSYM MEMBER_NOT_EMPTY] THEN DISCH_THEN(X_CHOOSE_TAC `a:A`) THEN
959 FIRST_ASSUM(MP_TAC o C MATCH_MP
960 (ASSUME `a:A IN d`) o last o CONJUNCTS) THEN
961 DISCH_THEN(MP_TAC o EXISTENCE) THEN
962 DISCH_THEN(X_CHOOSE_THEN `b:A#A` (CONJUNCTS_THEN ASSUME_TAC)) THEN
963 REWRITE_TAC[EXTENSION; NOT_FORALL_THM] THEN
964 EXISTS_TAC `(b:A#A,a:A)` THEN ASM_REWRITE_TAC[IN] THEN
965 DISCH_THEN(fun th -> FIRST_ASSUM
966 (MP_TAC o CONJUNCT2 o C MATCH_MP th o CONJUNCT1)) THEN
967 MAP_EVERY UNDISCH_TAC
968 [`a:A IN d`; `(d:A->bool) SUBSET (k DIFF s)`] THEN
969 REWRITE_TAC[SUBSET; IN_DIFF] THEN MESON_TAC[]] THEN
970 REWRITE_TAC[INFINITE; FINITE_UNION; DE_MORGAN_THM] THEN
971 ASM_REWRITE_TAC[GSYM INFINITE] THEN CONJ_TAC THENL
972 [MAP_EVERY UNDISCH_TAC
973 [`(d:A->bool) SUBSET (k DIFF s)`; `(s:A->bool) SUBSET k`] THEN
974 REWRITE_TAC[SUBSET; IN_UNION; IN_DIFF] THEN MESON_TAC[];
976 REPEAT(FIRST_ASSUM(UNDISCH_TAC o check is_conj o concl)) THEN
977 REWRITE_TAC[FORALL_PAIR_THM; EXISTS_UNIQUE_THM; EXISTS_PAIR_THM;
978 IN_CARD_MUL; IN_UNION; PAIR_EQ] THEN
979 MAP_EVERY UNDISCH_TAC
980 [`(s:A->bool) SUBSET k`;
981 `(d:A->bool) SUBSET (k DIFF s)`] THEN
982 REWRITE_TAC[SUBSET; EXTENSION; NOT_IN_EMPTY; IN_INTER; IN_DIFF] THEN
983 POP_ASSUM_LIST(K ALL_TAC) THEN
984 REPEAT DISCH_TAC THEN REPEAT CONJ_TAC THENL
985 [ASM_MESON_TAC[]; ASM_MESON_TAC[]; ALL_TAC] THEN
986 GEN_TAC THEN DISCH_THEN(DISJ_CASES_THEN MP_TAC) THENL
987 [ASM_MESON_TAC[]; ALL_TAC] THEN
988 DISCH_THEN(fun th -> CONJ_TAC THEN MP_TAC th) THENL
989 [ALL_TAC; ASM_MESON_TAC[]] THEN
991 FIRST_ASSUM(MP_TAC o C MATCH_MP th o last o CONJUNCTS)) THEN
994 (* ------------------------------------------------------------------------- *)
995 (* Preservation of finiteness. *)
996 (* ------------------------------------------------------------------------- *)
998 let CARD_ADD_FINITE = prove
999 (`!s t. FINITE s /\ FINITE t ==> FINITE(s +_c t)`,
1000 SIMP_TAC[add_c; FINITE_UNION; SIMPLE_IMAGE; FINITE_IMAGE]);;
1002 let CARD_ADD_FINITE_EQ = prove
1003 (`!s:A->bool t:B->bool. FINITE(s +_c t) <=> FINITE s /\ FINITE t`,
1004 REPEAT GEN_TAC THEN EQ_TAC THEN REWRITE_TAC[CARD_ADD_FINITE] THEN
1005 DISCH_THEN(fun th -> CONJ_TAC THEN MP_TAC th) THEN
1006 MATCH_MP_TAC(REWRITE_RULE[IMP_CONJ_ALT] CARD_LE_FINITE) THEN
1007 REWRITE_TAC[CARD_LE_ADDL; CARD_LE_ADDR]);;
1009 let CARD_MUL_FINITE = prove
1010 (`!s t. FINITE s /\ FINITE t ==> FINITE(s *_c t)`,
1011 SIMP_TAC[mul_c; FINITE_PRODUCT]);;
1013 (* ------------------------------------------------------------------------- *)
1014 (* Hence the "absorption laws" for arithmetic with an infinite cardinal. *)
1015 (* ------------------------------------------------------------------------- *)
1017 let CARD_MUL_ABSORB_LE = prove
1018 (`!s:A->bool t:B->bool. INFINITE(t) /\ s <=_c t ==> s *_c t <=_c t`,
1019 REPEAT STRIP_TAC THEN
1020 TRANS_TAC CARD_LE_TRANS `(t:B->bool) *_c t` THEN
1021 ASM_SIMP_TAC[CARD_LE_MUL; CARD_LE_REFL;
1022 CARD_SQUARE_INFINITE; CARD_EQ_IMP_LE]);;
1024 let CARD_MUL2_ABSORB_LE = prove
1025 (`!s:A->bool t:B->bool u:C->bool.
1026 INFINITE(u) /\ s <=_c u /\ t <=_c u ==> s *_c t <=_c u`,
1027 REPEAT STRIP_TAC THEN
1028 TRANS_TAC CARD_LE_TRANS `(s:A->bool) *_c (u:C->bool)` THEN
1029 ASM_SIMP_TAC[CARD_MUL_ABSORB_LE] THEN MATCH_MP_TAC CARD_LE_MUL THEN
1030 ASM_REWRITE_TAC[CARD_LE_REFL]);;
1032 let CARD_ADD_ABSORB_LE = prove
1033 (`!s:A->bool t:B->bool. INFINITE(t) /\ s <=_c t ==> s +_c t <=_c t`,
1034 REPEAT STRIP_TAC THEN
1035 TRANS_TAC CARD_LE_TRANS `(t:B->bool) *_c t` THEN
1036 ASM_SIMP_TAC[CARD_SQUARE_INFINITE; CARD_EQ_IMP_LE] THEN
1037 TRANS_TAC CARD_LE_TRANS `(t:B->bool) +_c t` THEN
1038 ASM_SIMP_TAC[CARD_ADD_LE_MUL_INFINITE; CARD_LE_ADD; CARD_LE_REFL]);;
1040 let CARD_ADD2_ABSORB_LE = prove
1041 (`!s:A->bool t:B->bool u:C->bool.
1042 INFINITE(u) /\ s <=_c u /\ t <=_c u ==> s +_c t <=_c u`,
1043 REPEAT STRIP_TAC THEN
1044 TRANS_TAC CARD_LE_TRANS `(s:A->bool) +_c (u:C->bool)` THEN
1045 ASM_SIMP_TAC[CARD_ADD_ABSORB_LE] THEN MATCH_MP_TAC CARD_LE_ADD THEN
1046 ASM_REWRITE_TAC[CARD_LE_REFL]);;
1048 let CARD_MUL_ABSORB = prove
1049 (`!s:A->bool t:B->bool.
1050 INFINITE(t) /\ ~(s = {}) /\ s <=_c t ==> s *_c t =_c t`,
1051 SIMP_TAC[GSYM CARD_LE_ANTISYM; CARD_MUL_ABSORB_LE] THEN REPEAT STRIP_TAC THEN
1052 FIRST_X_ASSUM(X_CHOOSE_TAC `a:A` o
1053 GEN_REWRITE_RULE I [GSYM MEMBER_NOT_EMPTY]) THEN
1054 REWRITE_TAC[le_c] THEN EXISTS_TAC `\x:B. (a:A,x)` THEN
1055 ASM_SIMP_TAC[IN_CARD_MUL; PAIR_EQ]);;
1057 let CARD_ADD_ABSORB = prove
1058 (`!s:A->bool t:B->bool. INFINITE(t) /\ s <=_c t ==> s +_c t =_c t`,
1059 SIMP_TAC[GSYM CARD_LE_ANTISYM; CARD_LE_ADDL; CARD_ADD_ABSORB_LE]);;
1061 let CARD_ADD2_ABSORB_LT = prove
1062 (`!s:A->bool t:B->bool u:C->bool.
1063 INFINITE u /\ s <_c u /\ t <_c u ==> s +_c t <_c u`,
1064 REPEAT STRIP_TAC THEN
1065 ASM_CASES_TAC `FINITE((s:A->bool) +_c (t:B->bool))` THEN
1066 ASM_SIMP_TAC[CARD_LT_FINITE_INFINITE] THEN
1067 DISJ_CASES_TAC(ISPECL [`s:A->bool`; `t:B->bool`] CARD_LE_TOTAL) THENL
1068 [ASM_CASES_TAC `FINITE(t:B->bool)` THENL
1069 [ASM_MESON_TAC[CARD_LE_FINITE; CARD_ADD_FINITE];
1070 TRANS_TAC CARD_LET_TRANS `t:B->bool`];
1071 ASM_CASES_TAC `FINITE(s:A->bool)` THENL
1072 [ASM_MESON_TAC[CARD_LE_FINITE; CARD_ADD_FINITE];
1073 TRANS_TAC CARD_LET_TRANS `s:A->bool`]] THEN
1074 ASM_REWRITE_TAC[] THEN
1075 MATCH_MP_TAC CARD_ADD2_ABSORB_LE THEN
1076 ASM_REWRITE_TAC[INFINITE; CARD_LE_REFL]);;
1078 let CARD_LT_ADD = prove
1079 (`!s:A->bool s':B->bool t:C->bool t':D->bool.
1080 s <_c s' /\ t <_c t' ==> s +_c t <_c s' +_c t'`,
1081 REPEAT STRIP_TAC THEN
1082 ASM_CASES_TAC `FINITE((s':B->bool) +_c (t':D->bool))` THENL
1083 [FIRST_X_ASSUM(STRIP_ASSUME_TAC o GEN_REWRITE_RULE I
1084 [CARD_ADD_FINITE_EQ]) THEN
1085 SUBGOAL_THEN `FINITE(s:A->bool) /\ FINITE(t:C->bool)`
1086 STRIP_ASSUME_TAC THENL
1087 [CONJ_TAC THEN FIRST_X_ASSUM(MATCH_MP_TAC o MATCH_MP
1088 (REWRITE_RULE[IMP_CONJ_ALT] CARD_LE_FINITE) o
1089 MATCH_MP CARD_LT_IMP_LE) THEN
1091 MAP_EVERY UNDISCH_TAC
1092 [`(s:A->bool) <_c (s':B->bool)`;
1093 `(t:C->bool) <_c (t':D->bool)`] THEN
1094 ASM_SIMP_TAC[CARD_LT_CARD; CARD_ADD_FINITE; CARD_ADD_C] THEN
1096 MATCH_MP_TAC CARD_ADD2_ABSORB_LT THEN ASM_REWRITE_TAC[INFINITE] THEN
1098 [TRANS_TAC CARD_LTE_TRANS `s':B->bool` THEN
1099 ASM_REWRITE_TAC[CARD_LE_ADDR];
1100 TRANS_TAC CARD_LTE_TRANS `t':D->bool` THEN
1101 ASM_REWRITE_TAC[CARD_LE_ADDL]]]);;
1103 (* ------------------------------------------------------------------------- *)
1104 (* Some more ad-hoc but useful theorems. *)
1105 (* ------------------------------------------------------------------------- *)
1107 let CARD_MUL_LT_LEMMA = prove
1108 (`!s t:B->bool u. s <=_c t /\ t <_c u /\ INFINITE u ==> s *_c t <_c u`,
1109 REPEAT GEN_TAC THEN ASM_CASES_TAC `FINITE(t:B->bool)` THENL
1110 [REPEAT(DISCH_THEN(CONJUNCTS_THEN2 ASSUME_TAC MP_TAC)) THEN
1111 ONCE_REWRITE_TAC[GSYM CONTRAPOS_THM] THEN
1112 REWRITE_TAC[CARD_NOT_LT; INFINITE] THEN
1113 ASM_MESON_TAC[CARD_LE_FINITE; CARD_MUL_FINITE];
1114 ASM_MESON_TAC[INFINITE; CARD_MUL_ABSORB_LE; CARD_LET_TRANS]]);;
1116 let CARD_MUL_LT_INFINITE = prove
1117 (`!s:A->bool t:B->bool u. s <_c u /\ t <_c u /\ INFINITE u ==> s *_c t <_c u`,
1119 DISJ_CASES_TAC(ISPECL [`s:A->bool`; `t:B->bool`] CARD_LE_TOTAL) THENL
1120 [ASM_MESON_TAC[CARD_MUL_SYM; CARD_MUL_LT_LEMMA];
1121 STRIP_TAC THEN TRANS_TAC CARD_LET_TRANS `t:B->bool *_c s:A->bool` THEN
1122 ASM_MESON_TAC[CARD_EQ_IMP_LE; CARD_MUL_SYM; CARD_MUL_LT_LEMMA]]);;
1124 (* ------------------------------------------------------------------------- *)
1125 (* Cantor's theorem. *)
1126 (* ------------------------------------------------------------------------- *)
1128 let CANTOR_THM = prove
1129 (`!s:A->bool. s <_c {t | t SUBSET s}`,
1130 GEN_TAC THEN REWRITE_TAC[lt_c] THEN CONJ_TAC THENL
1131 [REWRITE_TAC[le_c] THEN EXISTS_TAC `(=):A->A->bool` THEN
1132 REWRITE_TAC[FUN_EQ_THM; IN_ELIM_THM; SUBSET; IN] THEN MESON_TAC[];
1133 REWRITE_TAC[LE_C; IN_ELIM_THM; SURJECTIVE_RIGHT_INVERSE] THEN
1134 REWRITE_TAC[NOT_EXISTS_THM] THEN X_GEN_TAC `g:A->(A->bool)` THEN
1135 DISCH_THEN(MP_TAC o SPEC `\x:A. s(x) /\ ~(g x x)`) THEN
1136 REWRITE_TAC[SUBSET; IN; FUN_EQ_THM] THEN MESON_TAC[]]);;
1138 let CANTOR_THM_UNIV = prove
1139 (`(UNIV:A->bool) <_c (UNIV:(A->bool)->bool)`,
1140 MP_TAC(ISPEC `UNIV:A->bool` CANTOR_THM) THEN
1141 MATCH_MP_TAC EQ_IMP THEN AP_TERM_TAC THEN
1142 REWRITE_TAC[EXTENSION; SUBSET; IN_UNIV; IN_ELIM_THM]);;
1144 (* ------------------------------------------------------------------------- *)
1145 (* Lemmas about countability. *)
1146 (* ------------------------------------------------------------------------- *)
1148 let NUM_COUNTABLE = prove
1150 REWRITE_TAC[COUNTABLE; ge_c; CARD_LE_REFL]);;
1152 let COUNTABLE_ALT = prove
1153 (`!s. COUNTABLE s <=> s <=_c (:num)`,
1154 REWRITE_TAC[COUNTABLE; ge_c]);;
1156 let COUNTABLE_CASES = prove
1157 (`!s. COUNTABLE s <=> FINITE s \/ s =_c (:num)`,
1158 REWRITE_TAC[COUNTABLE_ALT; FINITE_CARD_LT; CARD_LE_LT]);;
1160 let CARD_LE_COUNTABLE = prove
1161 (`!s t:A->bool. COUNTABLE t /\ s <=_c t ==> COUNTABLE s`,
1162 REWRITE_TAC[COUNTABLE; ge_c] THEN REPEAT STRIP_TAC THEN
1163 TRANS_TAC CARD_LE_TRANS `t:A->bool` THEN ASM_REWRITE_TAC[]);;
1165 let CARD_EQ_COUNTABLE = prove
1166 (`!s t:A->bool. COUNTABLE t /\ s =_c t ==> COUNTABLE s`,
1167 REWRITE_TAC[GSYM CARD_LE_ANTISYM] THEN MESON_TAC[CARD_LE_COUNTABLE]);;
1169 let CARD_COUNTABLE_CONG = prove
1170 (`!s t. s =_c t ==> (COUNTABLE s <=> COUNTABLE t)`,
1171 REWRITE_TAC[GSYM CARD_LE_ANTISYM] THEN MESON_TAC[CARD_LE_COUNTABLE]);;
1173 let COUNTABLE_SUBSET = prove
1174 (`!s t:A->bool. COUNTABLE t /\ s SUBSET t ==> COUNTABLE s`,
1175 REWRITE_TAC[COUNTABLE; ge_c] THEN REPEAT STRIP_TAC THEN
1176 TRANS_TAC CARD_LE_TRANS `t:A->bool` THEN
1177 ASM_SIMP_TAC[CARD_LE_SUBSET]);;
1179 let COUNTABLE_RESTRICT = prove
1180 (`!s P. COUNTABLE s ==> COUNTABLE {x | x IN s /\ P x}`,
1182 MATCH_MP_TAC(REWRITE_RULE[IMP_CONJ_ALT] COUNTABLE_SUBSET) THEN
1185 let COUNTABLE_SUBSET_NUM = prove
1186 (`!s:num->bool. COUNTABLE s`,
1187 MESON_TAC[NUM_COUNTABLE; COUNTABLE_SUBSET; SUBSET_UNIV]);;
1189 let FINITE_IMP_COUNTABLE = prove
1190 (`!s. FINITE s ==> COUNTABLE s`,
1191 SIMP_TAC[FINITE_CARD_LT; lt_c; COUNTABLE; ge_c]);;
1193 let COUNTABLE_IMAGE = prove
1194 (`!f:A->B s. COUNTABLE s ==> COUNTABLE (IMAGE f s)`,
1195 REWRITE_TAC[COUNTABLE; ge_c] THEN REPEAT STRIP_TAC THEN
1196 TRANS_TAC CARD_LE_TRANS `s:A->bool` THEN
1197 ASM_SIMP_TAC[CARD_LE_IMAGE]);;
1199 let COUNTABLE_IMAGE_INJ_GENERAL = prove
1201 (!x y. x IN s /\ y IN s /\ f(x) = f(y) ==> x = y) /\
1203 ==> COUNTABLE {x | x IN s /\ f(x) IN A}`,
1204 REPEAT STRIP_TAC THEN
1205 FIRST_X_ASSUM(MP_TAC o GEN_REWRITE_RULE I [INJECTIVE_ON_LEFT_INVERSE]) THEN
1206 DISCH_THEN(X_CHOOSE_TAC `g:B->A`) THEN
1207 MATCH_MP_TAC COUNTABLE_SUBSET THEN EXISTS_TAC `IMAGE (g:B->A) A` THEN
1208 ASM_SIMP_TAC[COUNTABLE_IMAGE] THEN ASM SET_TAC[]);;
1210 let COUNTABLE_IMAGE_INJ_EQ = prove
1212 (!x y. x IN s /\ y IN s /\ (f(x) = f(y)) ==> (x = y))
1213 ==> (COUNTABLE(IMAGE f s) <=> COUNTABLE s)`,
1214 REPEAT STRIP_TAC THEN EQ_TAC THEN ASM_SIMP_TAC[COUNTABLE_IMAGE] THEN
1215 POP_ASSUM MP_TAC THEN REWRITE_TAC[IMP_IMP] THEN
1216 DISCH_THEN(MP_TAC o MATCH_MP COUNTABLE_IMAGE_INJ_GENERAL) THEN
1217 MATCH_MP_TAC EQ_IMP THEN AP_TERM_TAC THEN SET_TAC[]);;
1219 let COUNTABLE_IMAGE_INJ = prove
1221 (!x y. (f(x) = f(y)) ==> (x = y)) /\
1223 ==> COUNTABLE {x | f(x) IN A}`,
1225 MP_TAC(SPECL [`f:A->B`; `A:B->bool`; `UNIV:A->bool`]
1226 COUNTABLE_IMAGE_INJ_GENERAL) THEN REWRITE_TAC[IN_UNIV]);;
1228 let COUNTABLE_EMPTY = prove
1230 SIMP_TAC[FINITE_IMP_COUNTABLE; FINITE_RULES]);;
1232 let COUNTABLE_INTER = prove
1233 (`!s t. COUNTABLE s \/ COUNTABLE t ==> COUNTABLE (s INTER t)`,
1234 REWRITE_TAC[TAUT `(a \/ b ==> c) <=> (a ==> c) /\ (b ==> c)`] THEN
1235 REPEAT GEN_TAC THEN CONJ_TAC THEN
1236 MATCH_MP_TAC(REWRITE_RULE[IMP_CONJ_ALT] COUNTABLE_SUBSET) THEN
1239 let COUNTABLE_UNION_IMP = prove
1240 (`!s t:A->bool. COUNTABLE s /\ COUNTABLE t ==> COUNTABLE(s UNION t)`,
1241 REWRITE_TAC[COUNTABLE; ge_c] THEN REPEAT STRIP_TAC THEN
1242 TRANS_TAC CARD_LE_TRANS `(s:A->bool) +_c (t:A->bool)` THEN
1243 ASM_SIMP_TAC[CARD_ADD2_ABSORB_LE; num_INFINITE; UNION_LE_ADD_C]);;
1245 let COUNTABLE_UNION = prove
1246 (`!s t:A->bool. COUNTABLE(s UNION t) <=> COUNTABLE s /\ COUNTABLE t`,
1247 REPEAT GEN_TAC THEN EQ_TAC THEN REWRITE_TAC[COUNTABLE_UNION_IMP] THEN
1248 DISCH_THEN(fun th -> CONJ_TAC THEN MP_TAC th) THEN
1249 MATCH_MP_TAC(REWRITE_RULE[IMP_CONJ_ALT] COUNTABLE_SUBSET) THEN
1252 let COUNTABLE_SING = prove
1253 (`!x. COUNTABLE {x}`,
1254 SIMP_TAC[FINITE_IMP_COUNTABLE; FINITE_SING]);;
1256 let COUNTABLE_INSERT = prove
1257 (`!x s. COUNTABLE(x INSERT s) <=> COUNTABLE s`,
1258 ONCE_REWRITE_TAC[SET_RULE `x INSERT s = {x} UNION s`] THEN
1259 REWRITE_TAC[COUNTABLE_UNION; COUNTABLE_SING]);;
1261 let COUNTABLE_DELETE = prove
1262 (`!x:A s. COUNTABLE(s DELETE x) <=> COUNTABLE s`,
1263 REPEAT GEN_TAC THEN ASM_CASES_TAC `(x:A) IN s` THEN
1264 ASM_SIMP_TAC[SET_RULE `~(x IN s) ==> s DELETE x = s`] THEN
1265 MATCH_MP_TAC EQ_TRANS THEN
1266 EXISTS_TAC `COUNTABLE((x:A) INSERT (s DELETE x))` THEN CONJ_TAC THENL
1267 [REWRITE_TAC[COUNTABLE_INSERT]; AP_TERM_TAC THEN ASM SET_TAC[]]);;
1269 let COUNTABLE_DIFF_FINITE = prove
1270 (`!s t. FINITE s ==> (COUNTABLE(t DIFF s) <=> COUNTABLE t)`,
1271 REWRITE_TAC[RIGHT_FORALL_IMP_THM] THEN
1272 MATCH_MP_TAC FINITE_INDUCT_STRONG THEN
1273 SIMP_TAC[DIFF_EMPTY; SET_RULE `s DIFF (x INSERT t) = (s DIFF t) DELETE x`;
1274 COUNTABLE_DELETE]);;
1276 let COUNTABLE_CROSS = prove
1277 (`!s t. COUNTABLE s /\ COUNTABLE t ==> COUNTABLE(s CROSS t)`,
1278 REWRITE_TAC[COUNTABLE; ge_c; CROSS; GSYM mul_c] THEN
1279 SIMP_TAC[CARD_MUL2_ABSORB_LE; num_INFINITE]);;
1281 let COUNTABLE_AS_IMAGE_SUBSET = prove
1282 (`!s. COUNTABLE s ==> ?f. s SUBSET (IMAGE f (:num))`,
1283 REWRITE_TAC[COUNTABLE; ge_c; LE_C; SUBSET; IN_IMAGE] THEN MESON_TAC[]);;
1285 let COUNTABLE_AS_IMAGE_SUBSET_EQ = prove
1286 (`!s:A->bool. COUNTABLE s <=> ?f. s SUBSET (IMAGE f (:num))`,
1287 REWRITE_TAC[COUNTABLE; ge_c; LE_C; SUBSET; IN_IMAGE] THEN MESON_TAC[]);;
1289 let COUNTABLE_AS_IMAGE = prove
1290 (`!s:A->bool. COUNTABLE s /\ ~(s = {}) ==> ?f. s = IMAGE f (:num)`,
1291 REPEAT STRIP_TAC THEN FIRST_X_ASSUM(X_CHOOSE_TAC `a:A` o
1292 GEN_REWRITE_RULE I [GSYM MEMBER_NOT_EMPTY]) THEN
1293 FIRST_X_ASSUM(MP_TAC o MATCH_MP COUNTABLE_AS_IMAGE_SUBSET) THEN
1294 DISCH_THEN(X_CHOOSE_TAC `f:num->A`) THEN
1295 EXISTS_TAC `\n. if (f:num->A) n IN s then f n else a` THEN
1298 let FORALL_COUNTABLE_AS_IMAGE = prove
1299 (`(!d. COUNTABLE d ==> P d) <=> P {} /\ (!f. P(IMAGE f (:num)))`,
1300 MESON_TAC[COUNTABLE_AS_IMAGE; COUNTABLE_IMAGE; NUM_COUNTABLE;
1303 let COUNTABLE_AS_INJECTIVE_IMAGE = prove
1304 (`!s. COUNTABLE s /\ INFINITE s
1305 ==> ?f. s = IMAGE f (:num) /\ (!m n. f(m) = f(n) ==> m = n)`,
1306 GEN_TAC THEN ONCE_REWRITE_TAC[CONJ_SYM] THEN
1307 REWRITE_TAC[INFINITE_CARD_LE; COUNTABLE; ge_c] THEN
1308 REWRITE_TAC[CARD_LE_ANTISYM; eq_c] THEN
1309 MATCH_MP_TAC MONO_EXISTS THEN SET_TAC[]);;
1311 let COUNTABLE_UNIONS = prove
1312 (`!A:(A->bool)->bool.
1313 COUNTABLE A /\ (!s. s IN A ==> COUNTABLE s)
1314 ==> COUNTABLE (UNIONS A)`,
1316 GEN_REWRITE_TAC (LAND_CONV o TOP_DEPTH_CONV)
1317 [COUNTABLE_AS_IMAGE_SUBSET_EQ] THEN
1318 DISCH_THEN(CONJUNCTS_THEN2 (X_CHOOSE_TAC `f:num->A->bool`) MP_TAC) THEN
1319 GEN_REWRITE_TAC (LAND_CONV o BINDER_CONV) [RIGHT_IMP_EXISTS_THM] THEN
1320 REWRITE_TAC[SKOLEM_THM] THEN
1321 DISCH_THEN(X_CHOOSE_TAC `g:(A->bool)->num->A`) THEN
1322 MATCH_MP_TAC COUNTABLE_SUBSET THEN
1323 EXISTS_TAC `IMAGE (\(m,n). (g:(A->bool)->num->A) ((f:num->A->bool) m) n)
1324 ((:num) CROSS (:num))` THEN
1325 ASM_SIMP_TAC[COUNTABLE_IMAGE; COUNTABLE_CROSS; NUM_COUNTABLE] THEN
1326 REWRITE_TAC[SUBSET; FORALL_IN_UNIONS] THEN
1327 REWRITE_TAC[IN_IMAGE; EXISTS_PAIR_THM; IN_CROSS; IN_UNIV] THEN
1330 let COUNTABLE_PRODUCT_DEPENDENT = prove
1332 COUNTABLE s /\ (!x. x IN s ==> COUNTABLE(t x))
1333 ==> COUNTABLE {f x y | x IN s /\ y IN (t x)}`,
1334 REPEAT GEN_TAC THEN DISCH_TAC THEN
1335 SUBGOAL_THEN `{(f:A->B->C) x y | x IN s /\ y IN (t x)} =
1336 IMAGE (\(x,y). f x y) {(x,y) | x IN s /\ y IN (t x)}`
1338 [REWRITE_TAC[EXTENSION; IN_IMAGE; EXISTS_PAIR_THM; IN_ELIM_PAIR_THM] THEN
1340 MATCH_MP_TAC COUNTABLE_IMAGE THEN POP_ASSUM MP_TAC] THEN
1341 GEN_REWRITE_TAC (LAND_CONV o TOP_DEPTH_CONV)
1342 [COUNTABLE_AS_IMAGE_SUBSET_EQ] THEN
1343 DISCH_THEN(CONJUNCTS_THEN2 (X_CHOOSE_TAC `f:num->A`) MP_TAC) THEN
1344 GEN_REWRITE_TAC (LAND_CONV o BINDER_CONV) [RIGHT_IMP_EXISTS_THM] THEN
1345 REWRITE_TAC[SKOLEM_THM] THEN
1346 DISCH_THEN(X_CHOOSE_TAC `g:A->num->B`) THEN
1347 MATCH_MP_TAC COUNTABLE_SUBSET THEN
1348 EXISTS_TAC `IMAGE (\(m,n). (f:num->A) m,(g:A->num->B)(f m) n)
1349 ((:num) CROSS (:num))` THEN
1350 ASM_SIMP_TAC[COUNTABLE_IMAGE; COUNTABLE_CROSS; NUM_COUNTABLE] THEN
1351 REWRITE_TAC[SUBSET; FORALL_IN_UNIONS] THEN
1352 REWRITE_TAC[IN_IMAGE; FORALL_PAIR_THM; IN_ELIM_PAIR_THM;
1353 EXISTS_PAIR_THM; IN_CROSS; IN_UNIV] THEN
1356 let COUNTABLE_CARD_MUL = prove
1357 (`!s:A->bool t:B->bool. COUNTABLE s /\ COUNTABLE t ==> COUNTABLE(s *_c t)`,
1358 REPEAT STRIP_TAC THEN REWRITE_TAC[mul_c] THEN
1359 ASM_SIMP_TAC[COUNTABLE_PRODUCT_DEPENDENT]);;
1361 let COUNTABLE_CARD_MUL_EQ = prove
1362 (`!s:A->bool t:B->bool.
1363 COUNTABLE(s *_c t) <=> s = {} \/ t = {} \/ COUNTABLE s /\ COUNTABLE t`,
1364 REPEAT GEN_TAC THEN REWRITE_TAC[mul_c] THEN
1365 MAP_EVERY ASM_CASES_TAC [`s:A->bool = {}`; `t:B->bool = {}`] THEN
1366 ASM_REWRITE_TAC[COUNTABLE_EMPTY; EMPTY_GSPEC; NOT_IN_EMPTY;
1367 SET_RULE `{x,y | F} = {}`] THEN
1368 EQ_TAC THEN SIMP_TAC[REWRITE_RULE[mul_c] COUNTABLE_CARD_MUL] THEN
1369 REPEAT STRIP_TAC THEN MATCH_MP_TAC COUNTABLE_SUBSET THENL
1370 [EXISTS_TAC `IMAGE FST ((s:A->bool) *_c (t:B->bool))`;
1371 EXISTS_TAC `IMAGE SND ((s:A->bool) *_c (t:B->bool))`] THEN
1372 ASM_SIMP_TAC[COUNTABLE_IMAGE; mul_c; SUBSET; IN_IMAGE; EXISTS_PAIR_THM] THEN
1373 REWRITE_TAC[IN_ELIM_PAIR_THM] THEN ASM SET_TAC[]);;
1375 let CARD_EQ_PCROSS = prove
1376 (`!s:A^M->bool t:A^N->bool. s PCROSS t =_c s *_c t`,
1377 REPEAT GEN_TAC THEN REWRITE_TAC[EQ_C_BIJECTIONS; mul_c] THEN
1378 EXISTS_TAC `\z:A^(M,N)finite_sum. fstcart z,sndcart z` THEN
1379 EXISTS_TAC `\(x:A^M,y:A^N). pastecart x y` THEN
1380 REWRITE_TAC[FORALL_IN_GSPEC; PASTECART_IN_PCROSS] THEN
1381 REWRITE_TAC[IN_ELIM_PAIR_THM; PASTECART_FST_SND] THEN
1382 REWRITE_TAC[FORALL_IN_PCROSS; FSTCART_PASTECART; SNDCART_PASTECART]);;
1384 let COUNTABLE_PCROSS_EQ = prove
1385 (`!s:A^M->bool t:A^N->bool.
1386 COUNTABLE(s PCROSS t) <=>
1387 s = {} \/ t = {} \/ COUNTABLE s /\ COUNTABLE t`,
1388 REPEAT GEN_TAC THEN MATCH_MP_TAC EQ_TRANS THEN
1389 EXISTS_TAC `COUNTABLE((s:A^M->bool) *_c (t:A^N->bool))` THEN CONJ_TAC THENL
1390 [MATCH_MP_TAC CARD_COUNTABLE_CONG THEN REWRITE_TAC[CARD_EQ_PCROSS];
1391 REWRITE_TAC[COUNTABLE_CARD_MUL_EQ]]);;
1393 let COUNTABLE_PCROSS = prove
1394 (`!s:A^M->bool t:A^N->bool.
1395 COUNTABLE s /\ COUNTABLE t ==> COUNTABLE(s PCROSS t)`,
1396 SIMP_TAC[COUNTABLE_PCROSS_EQ]);;
1398 let COUNTABLE_CART = prove
1399 (`!P. (!i. 1 <= i /\ i <= dimindex(:N) ==> COUNTABLE {x | P i x})
1400 ==> COUNTABLE {v:A^N | !i. 1 <= i /\ i <= dimindex(:N) ==> P i (v$i)}`,
1401 GEN_TAC THEN DISCH_TAC THEN
1403 `!n. n <= dimindex(:N)
1404 ==> COUNTABLE {v:A^N | (!i. 1 <= i /\ i <= dimindex(:N) /\ i <= n
1406 (!i. 1 <= i /\ i <= dimindex(:N) /\ n < i
1408 (MP_TAC o SPEC `dimindex(:N)`) THEN REWRITE_TAC[LE_REFL; LET_ANTISYM] THEN
1410 [REWRITE_TAC[ARITH_RULE `1 <= i /\ i <= n /\ i <= 0 <=> F`] THEN
1411 SIMP_TAC[ARITH_RULE `1 <= i /\ i <= n /\ 0 < i <=> 1 <= i /\ i <= n`] THEN
1413 `{v | !i. 1 <= i /\ i <= dimindex (:N) ==> v$i = (@x. F)} =
1414 {(lambda i. @x. F):A^N}`
1415 (fun th -> SIMP_TAC[COUNTABLE_SING;th]) THEN
1416 SIMP_TAC[EXTENSION; IN_SING; IN_ELIM_THM; CART_EQ; LAMBDA_BETA];
1419 MATCH_MP_TAC COUNTABLE_SUBSET THEN EXISTS_TAC
1420 `IMAGE (\(x:A,v:A^N). (lambda i. if i = SUC n then x else v$i):A^N)
1421 {x,v | x IN {x:A | P (SUC n) x} /\
1422 v IN {v:A^N | (!i. 1 <= i /\ i <= dimindex(:N) /\ i <= n
1424 (!i. 1 <= i /\ i <= dimindex (:N) /\ n < i
1425 ==> v$i = (@x. F))}}` THEN
1427 [MATCH_MP_TAC COUNTABLE_IMAGE THEN
1428 ASM_SIMP_TAC[REWRITE_RULE[CROSS] COUNTABLE_CROSS; ARITH_RULE `1 <= SUC n`;
1429 ARITH_RULE `SUC n <= m ==> n <= m`];
1431 REWRITE_TAC[SUBSET; IN_IMAGE; IN_ELIM_PAIR_THM; EXISTS_PAIR_THM] THEN
1432 X_GEN_TAC `v:A^N` THEN REWRITE_TAC[IN_ELIM_THM] THEN
1433 STRIP_TAC THEN EXISTS_TAC `(v:A^N)$(SUC n)` THEN
1434 EXISTS_TAC `(lambda i. if i = SUC n then @x. F else (v:A^N)$i):A^N` THEN
1435 SIMP_TAC[CART_EQ; LAMBDA_BETA; ARITH_RULE `i <= n ==> ~(i = SUC n)`] THEN
1436 ASM_MESON_TAC[LE; ARITH_RULE `1 <= SUC n`;
1437 ARITH_RULE `n < i /\ ~(i = SUC n) ==> SUC n < i`]);;
1439 let COUNTABLE_SUBSET_IMAGE = prove
1441 COUNTABLE(t) /\ t SUBSET (IMAGE f s) <=>
1442 ?s'. COUNTABLE s' /\ s' SUBSET s /\ (t = IMAGE f s')`,
1443 REPEAT GEN_TAC THEN EQ_TAC THENL
1444 [ALL_TAC; ASM_MESON_TAC[COUNTABLE_IMAGE; IMAGE_SUBSET]] THEN
1446 EXISTS_TAC `IMAGE (\y. @x. x IN s /\ ((f:A->B)(x) = y)) t` THEN
1447 ASM_SIMP_TAC[COUNTABLE_IMAGE] THEN
1448 REWRITE_TAC[EXTENSION; SUBSET; FORALL_IN_IMAGE] THEN CONJ_TAC THENL
1449 [ASM_MESON_TAC[SUBSET; IN_IMAGE]; ALL_TAC] THEN
1450 REWRITE_TAC[IN_IMAGE] THEN X_GEN_TAC `y:B` THEN
1451 REWRITE_TAC[RIGHT_AND_EXISTS_THM] THEN
1452 ONCE_REWRITE_TAC[SWAP_EXISTS_THM] THEN ONCE_REWRITE_TAC[CONJ_SYM] THEN
1453 REWRITE_TAC[UNWIND_THM2; GSYM CONJ_ASSOC] THEN
1454 ASM_MESON_TAC[SUBSET; IN_IMAGE]);;
1456 let EXISTS_COUNTABLE_SUBSET_IMAGE = prove
1458 (?t. COUNTABLE t /\ t SUBSET IMAGE f s /\ P t) <=>
1459 (?t. COUNTABLE t /\ t SUBSET s /\ P (IMAGE f t))`,
1460 REWRITE_TAC[COUNTABLE_SUBSET_IMAGE; CONJ_ASSOC] THEN MESON_TAC[]);;
1462 let FORALL_COUNTABLE_SUBSET_IMAGE = prove
1463 (`!P f s. (!t. COUNTABLE t /\ t SUBSET IMAGE f s ==> P t) <=>
1464 (!t. COUNTABLE t /\ t SUBSET s ==> P(IMAGE f t))`,
1466 ONCE_REWRITE_TAC[MESON[] `(!x. P x) <=> ~(?x. ~P x)`] THEN
1467 REWRITE_TAC[NOT_IMP; GSYM CONJ_ASSOC; EXISTS_COUNTABLE_SUBSET_IMAGE]);;
1469 (* ------------------------------------------------------------------------- *)
1470 (* Cardinality of infinite list and cartesian product types. *)
1471 (* ------------------------------------------------------------------------- *)
1473 let CARD_EQ_LIST_GEN = prove
1474 (`!s:A->bool. INFINITE(s) ==> {l | !x. MEM x l ==> x IN s} =_c s`,
1475 GEN_TAC THEN DISCH_TAC THEN
1476 REWRITE_TAC[GSYM CARD_LE_ANTISYM] THEN CONJ_TAC THENL
1478 REWRITE_TAC[le_c; IN_UNIV] THEN
1479 EXISTS_TAC `\x:A. [x]` THEN SIMP_TAC[CONS_11; IN_ELIM_THM; MEM]] THEN
1480 TRANS_TAC CARD_LE_TRANS `(:num) *_c (s:A->bool)` THEN CONJ_TAC THENL
1482 MATCH_MP_TAC CARD_MUL2_ABSORB_LE THEN
1483 ASM_REWRITE_TAC[GSYM INFINITE_CARD_LE; CARD_LE_REFL]] THEN
1484 SUBGOAL_THEN `s *_c s <=_c (s:A->bool)` MP_TAC THENL
1485 [MATCH_MP_TAC CARD_MUL2_ABSORB_LE THEN ASM_REWRITE_TAC[CARD_LE_REFL];
1487 REWRITE_TAC[le_c; mul_c; FORALL_PAIR_THM; IN_ELIM_PAIR_THM; PAIR_EQ] THEN
1488 REWRITE_TAC[IN_UNIV; LEFT_IMP_EXISTS_THM] THEN
1489 GEN_REWRITE_TAC I [FORALL_CURRY] THEN
1490 X_GEN_TAC `pair:A->A->A` THEN REWRITE_TAC[IN_ELIM_THM] THEN STRIP_TAC THEN
1491 SUBGOAL_THEN `?b:A. b IN s` CHOOSE_TAC THENL
1492 [ASM_MESON_TAC[INFINITE; FINITE_EMPTY; MEMBER_NOT_EMPTY]; ALL_TAC] THEN
1493 EXISTS_TAC `\l. LENGTH l,ITLIST (pair:A->A->A) l b` THEN
1494 REWRITE_TAC[PAIR_EQ; RIGHT_EXISTS_AND_THM; GSYM EXISTS_REFL] THEN
1496 `!l:A list. (!x. MEM x l ==> x IN s) ==> (ITLIST pair l b) IN s`
1498 [LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[MEM; ITLIST] THEN ASM_MESON_TAC[];
1499 CONJ_TAC THENL [ASM_MESON_TAC[]; ALL_TAC]] THEN
1500 ONCE_REWRITE_TAC[SWAP_FORALL_THM] THEN
1501 LIST_INDUCT_TAC THEN SIMP_TAC[LENGTH_EQ_NIL; LENGTH] THEN
1502 LIST_INDUCT_TAC THEN REWRITE_TAC[LENGTH; NOT_SUC] THEN
1503 REWRITE_TAC[ITLIST; SUC_INJ; MEM; CONS_11] THEN
1504 REPEAT STRIP_TAC THENL [ALL_TAC; FIRST_X_ASSUM MATCH_MP_TAC] THEN
1507 let CARD_EQ_LIST = prove
1508 (`INFINITE(:A) ==> (:A list) =_c (:A)`,
1509 DISCH_THEN(MP_TAC o MATCH_MP CARD_EQ_LIST_GEN) THEN
1510 REWRITE_TAC[IN_UNIV; SET_RULE `{x | T} = UNIV`]);;
1512 let CARD_EQ_CART = prove
1513 (`INFINITE(:A) ==> (:A^N) =_c (:A)`,
1514 DISCH_TAC THEN REWRITE_TAC[GSYM CARD_LE_ANTISYM] THEN CONJ_TAC THENL
1516 REWRITE_TAC[le_c; IN_UNIV] THEN
1517 EXISTS_TAC `(\x. lambda i. x):A->A^N` THEN
1518 SIMP_TAC[CART_EQ; LAMBDA_BETA] THEN
1519 MESON_TAC[LE_REFL; DIMINDEX_GE_1]] THEN
1520 TRANS_TAC CARD_LE_TRANS `(:A list)` THEN
1521 ASM_SIMP_TAC[CARD_EQ_LIST; CARD_EQ_IMP_LE] THEN REWRITE_TAC[LE_C] THEN
1522 EXISTS_TAC `(\l. lambda i. EL i l):(A)list->A^N` THEN
1523 ASM_SIMP_TAC[CART_EQ; IN_UNIV; LAMBDA_BETA] THEN X_GEN_TAC `x:A^N` THEN
1524 SUBGOAL_THEN `!n f. ?l. !i. i < n ==> EL i l:A = f i` MP_TAC THENL
1525 [INDUCT_TAC THEN REWRITE_TAC[CONJUNCT1 LT] THEN X_GEN_TAC `f:num->A` THEN
1526 FIRST_X_ASSUM(MP_TAC o SPEC `\i. (f:num->A)(SUC i)`) THEN
1527 REWRITE_TAC[LEFT_IMP_EXISTS_THM] THEN X_GEN_TAC `l:A list` THEN
1528 DISCH_TAC THEN EXISTS_TAC `CONS ((f:num->A) 0) l` THEN
1529 INDUCT_TAC THEN ASM_SIMP_TAC[EL; HD; TL; LT_SUC];
1530 DISCH_THEN(MP_TAC o SPECL [`dimindex(:N)+1`; `\i. (x:A^N)$i`]) THEN
1531 REWRITE_TAC[LEFT_IMP_EXISTS_THM; ARITH_RULE `i < n + 1 <=> i <= n`] THEN
1534 (* ------------------------------------------------------------------------- *)
1535 (* Cardinality of the reals. This is done in a rather laborious way to avoid *)
1536 (* any dependence on the theories of analysis. *)
1537 (* ------------------------------------------------------------------------- *)
1539 let CARD_EQ_REAL = prove
1540 (`(:real) =_c (:num->bool)`,
1542 (`!s m n. sum (s INTER (m..n)) (\i. inv(&3 pow i)) < &3 / &2 / &3 pow m`,
1543 REPEAT GEN_TAC THEN MATCH_MP_TAC REAL_LET_TRANS THEN
1544 EXISTS_TAC `sum (m..n) (\i. inv(&3 pow i))` THEN CONJ_TAC THENL
1545 [MATCH_MP_TAC SUM_SUBSET_SIMPLE THEN
1546 SIMP_TAC[FINITE_NUMSEG; INTER_SUBSET; REAL_LE_INV_EQ;
1547 REAL_POW_LE; REAL_POS];
1548 WF_INDUCT_TAC `n - m:num` THEN
1549 ASM_CASES_TAC `m:num <= n` THENL
1550 [ASM_SIMP_TAC[SUM_CLAUSES_LEFT] THEN ASM_CASES_TAC `m + 1 <= n` THENL
1551 [FIRST_X_ASSUM(MP_TAC o SPECL [`n:num`; `SUC m`]) THEN
1552 ANTS_TAC THENL [ASM_ARITH_TAC; REWRITE_TAC[ADD1; REAL_POW_ADD]] THEN
1553 MATCH_MP_TAC(REAL_ARITH
1554 `a + j:real <= k ==> x < j ==> a + x < k`) THEN
1555 REWRITE_TAC[real_div; REAL_INV_MUL; REAL_POW_1] THEN REAL_ARITH_TAC;
1558 RULE_ASSUM_TAC(REWRITE_RULE[NOT_LE; GSYM NUMSEG_EMPTY]) THEN
1559 ASM_REWRITE_TAC[SUM_CLAUSES; REAL_ADD_RID] THEN
1560 REWRITE_TAC[REAL_ARITH `inv x < &3 / &2 / x <=> &0 < inv x`] THEN
1561 SIMP_TAC[REAL_LT_INV_EQ; REAL_LT_DIV; REAL_POW_LT; REAL_OF_NUM_LT;
1563 REWRITE_TAC[GSYM CARD_LE_ANTISYM] THEN CONJ_TAC THENL
1564 [TRANS_TAC CARD_LE_TRANS `(:num) *_c (:num->bool)` THEN CONJ_TAC THENL
1566 MATCH_MP_TAC CARD_MUL2_ABSORB_LE THEN REWRITE_TAC[INFINITE_CARD_LE] THEN
1567 SIMP_TAC[CANTOR_THM_UNIV; CARD_LT_IMP_LE; CARD_LE_REFL]] THEN
1568 TRANS_TAC CARD_LE_TRANS `(:num) *_c {x:real | &0 <= x}` THEN CONJ_TAC THENL
1569 [REWRITE_TAC[LE_C; mul_c; EXISTS_PAIR_THM; IN_ELIM_PAIR_THM; IN_UNIV] THEN
1570 EXISTS_TAC `\(n,x:real). --(&1) pow n * x` THEN X_GEN_TAC `x:real` THEN
1571 MATCH_MP_TAC(MESON[] `P 0 \/ P 1 ==> ?n. P n`) THEN
1572 REWRITE_TAC[OR_EXISTS_THM] THEN EXISTS_TAC `abs x` THEN
1573 REWRITE_TAC[IN_ELIM_THM] THEN REAL_ARITH_TAC;
1575 MATCH_MP_TAC CARD_LE_MUL THEN REWRITE_TAC[CARD_LE_REFL] THEN
1576 MP_TAC(ISPECL [`(:num)`; `(:num)`] CARD_MUL_ABSORB_LE) THEN
1577 REWRITE_TAC[CARD_LE_REFL; num_INFINITE] THEN
1578 REWRITE_TAC[le_c; mul_c; IN_UNIV; FORALL_PAIR_THM; IN_ELIM_PAIR_THM] THEN
1579 REWRITE_TAC[GSYM FORALL_PAIR_THM; INJECTIVE_LEFT_INVERSE] THEN
1580 REWRITE_TAC[LEFT_IMP_EXISTS_THM] THEN
1581 MAP_EVERY X_GEN_TAC [`pair:num#num->num`; `unpair:num->num#num`] THEN
1583 EXISTS_TAC `\x:real n:num. &(FST(unpair n)) * x <= &(SND(unpair n))` THEN
1584 MATCH_MP_TAC REAL_WLOG_LT THEN REWRITE_TAC[IN_ELIM_THM; FUN_EQ_THM] THEN
1585 CONJ_TAC THENL [REWRITE_TAC[EQ_SYM_EQ; CONJ_ACI]; ALL_TAC] THEN
1586 MAP_EVERY X_GEN_TAC [`x:real`; `y:real`] THEN REPEAT STRIP_TAC THEN
1587 FIRST_X_ASSUM(MP_TAC o GENL [`p:num`; `q:num`] o
1588 SPEC `(pair:num#num->num) (p,q)`) THEN
1589 ASM_REWRITE_TAC[] THEN MATCH_MP_TAC(TAUT `~p ==> p ==> q`) THEN
1590 MP_TAC(SPEC `y - x:real` REAL_ARCH) THEN
1591 ASM_REWRITE_TAC[REAL_SUB_LT; NOT_FORALL_THM] THEN
1592 DISCH_THEN(MP_TAC o SPEC `&2`) THEN MATCH_MP_TAC MONO_EXISTS THEN
1593 X_GEN_TAC `p:num` THEN DISCH_TAC THEN
1594 MP_TAC(ISPEC `&p * x:real` REAL_ARCH_LT) THEN
1595 GEN_REWRITE_TAC LAND_CONV [num_WOP] THEN MATCH_MP_TAC MONO_EXISTS THEN
1596 MATCH_MP_TAC num_INDUCTION THEN
1597 ASM_SIMP_TAC[REAL_LE_MUL; REAL_POS;
1598 REAL_ARITH `x:real < &0 <=> ~(&0 <= x)`] THEN
1599 X_GEN_TAC `q:num` THEN REWRITE_TAC[GSYM REAL_OF_NUM_SUC] THEN
1600 DISCH_THEN(K ALL_TAC) THEN STRIP_TAC THEN
1601 FIRST_X_ASSUM(MP_TAC o SPEC `q:num`) THEN
1602 REWRITE_TAC[LT] THEN ASM_REAL_ARITH_TAC;
1603 REWRITE_TAC[le_c; IN_UNIV] THEN
1604 EXISTS_TAC `\s:num->bool. sup { sum (s INTER (0..n)) (\i. inv(&3 pow i)) |
1606 MAP_EVERY X_GEN_TAC [`x:num->bool`; `y:num->bool`] THEN
1607 ONCE_REWRITE_TAC[GSYM CONTRAPOS_THM] THEN
1608 REWRITE_TAC[EXTENSION; NOT_FORALL_THM] THEN
1609 GEN_REWRITE_TAC LAND_CONV [num_WOP] THEN
1610 MAP_EVERY (fun w -> SPEC_TAC(w,w)) [`y:num->bool`; `x:num->bool`] THEN
1611 MATCH_MP_TAC(MESON[IN]
1612 `((!P Q n. R P Q n <=> R Q P n) /\ (!P Q. S P Q <=> S Q P)) /\
1613 (!P Q. (?n. n IN P /\ ~(n IN Q) /\ R P Q n) ==> S P Q)
1614 ==> !P Q. (?n:num. ~(n IN P <=> n IN Q) /\ R P Q n) ==> S P Q`) THEN
1615 CONJ_TAC THENL [REWRITE_TAC[EQ_SYM_EQ]; REWRITE_TAC[]] THEN
1616 MAP_EVERY X_GEN_TAC [`x:num->bool`; `y:num->bool`] THEN
1617 DISCH_THEN(X_CHOOSE_THEN `n:num` STRIP_ASSUME_TAC) THEN
1618 MATCH_MP_TAC(REAL_ARITH `!z:real. y < z /\ z <= x ==> ~(x = y)`) THEN
1619 EXISTS_TAC `sum (x INTER (0..n)) (\i. inv(&3 pow i))` THEN CONJ_TAC THENL
1620 [MATCH_MP_TAC REAL_LET_TRANS THEN EXISTS_TAC
1621 `sum (y INTER (0..n)) (\i. inv(&3 pow i)) +
1622 &3 / &2 / &3 pow (SUC n)` THEN
1624 [MATCH_MP_TAC REAL_SUP_LE THEN
1625 CONJ_TAC THENL [SET_TAC[]; REWRITE_TAC[FORALL_IN_GSPEC; IN_UNIV]] THEN
1626 X_GEN_TAC `p:num` THEN ASM_CASES_TAC `n:num <= p` THENL
1627 [MATCH_MP_TAC(REAL_ARITH
1628 `!d. s:real = t + d /\ d <= e ==> s <= t + e`) THEN
1629 EXISTS_TAC `sum(y INTER (n+1..p)) (\i. inv (&3 pow i))` THEN
1631 [ONCE_REWRITE_TAC[INTER_COMM] THEN
1632 REWRITE_TAC[INTER; SUM_RESTRICT_SET] THEN
1633 ASM_SIMP_TAC[SUM_COMBINE_R; LE_0];
1634 SIMP_TAC[ADD1; lemma; REAL_LT_IMP_LE]];
1635 MATCH_MP_TAC(REAL_ARITH `y:real <= x /\ &0 <= d ==> y <= x + d`) THEN
1636 SIMP_TAC[REAL_LE_DIV; REAL_POS; REAL_POW_LE] THEN
1637 MATCH_MP_TAC SUM_SUBSET_SIMPLE THEN
1638 SIMP_TAC[REAL_LE_INV_EQ; REAL_POW_LE; REAL_POS] THEN
1639 SIMP_TAC[FINITE_INTER; FINITE_NUMSEG] THEN MATCH_MP_TAC
1640 (SET_RULE `s SUBSET t ==> u INTER s SUBSET u INTER t`) THEN
1641 REWRITE_TAC[SUBSET_NUMSEG] THEN ASM_ARITH_TAC];
1642 ONCE_REWRITE_TAC[INTER_COMM] THEN
1643 REWRITE_TAC[INTER; SUM_RESTRICT_SET] THEN ASM_CASES_TAC `n = 0` THENL
1644 [FIRST_X_ASSUM SUBST_ALL_TAC THEN
1645 ASM_REWRITE_TAC[SUM_SING; NUMSEG_SING; real_pow] THEN REAL_ARITH_TAC;
1646 ASM_SIMP_TAC[SUM_CLAUSES_RIGHT; LE_1; LE_0; REAL_ADD_RID] THEN
1647 MATCH_MP_TAC(REAL_ARITH `s:real = t /\ d < e ==> s + d < t + e`) THEN
1649 [MATCH_MP_TAC SUM_EQ_NUMSEG THEN
1650 ASM_SIMP_TAC[ARITH_RULE `~(n = 0) /\ m <= n - 1 ==> m < n`];
1651 REWRITE_TAC[real_pow; real_div; REAL_INV_MUL; REAL_MUL_ASSOC] THEN
1652 CONV_TAC REAL_RAT_REDUCE_CONV THEN
1653 REWRITE_TAC[REAL_ARITH `&1 / &2 * x < x <=> &0 < x`] THEN
1654 SIMP_TAC[REAL_LT_INV_EQ; REAL_POW_LT; REAL_OF_NUM_LT; ARITH]]]];
1655 MP_TAC(ISPEC `{ sum (x INTER (0..n)) (\i. inv(&3 pow i)) | n IN (:num) }`
1656 SUP) THEN REWRITE_TAC[FORALL_IN_GSPEC; IN_UNIV] THEN
1657 ANTS_TAC THENL [ALL_TAC; SIMP_TAC[]] THEN
1658 CONJ_TAC THENL [SET_TAC[]; ALL_TAC] THEN
1659 EXISTS_TAC `&3 / &2 / &3 pow 0` THEN
1660 SIMP_TAC[lemma; REAL_LT_IMP_LE]]]);;
1662 let UNCOUNTABLE_REAL = prove
1663 (`~COUNTABLE(:real)`,
1664 REWRITE_TAC[COUNTABLE; CARD_NOT_LE; ge_c] THEN
1665 TRANS_TAC CARD_LTE_TRANS `(:num->bool)` THEN
1666 REWRITE_TAC[CANTOR_THM_UNIV] THEN MATCH_MP_TAC CARD_EQ_IMP_LE THEN
1667 ONCE_REWRITE_TAC[CARD_EQ_SYM] THEN REWRITE_TAC[CARD_EQ_REAL]);;
1669 let CARD_EQ_REAL_IMP_UNCOUNTABLE = prove
1670 (`!(s : A -> bool). s =_c (:real) ==> ~COUNTABLE s`,
1671 GEN_TAC THEN STRIP_TAC THEN
1672 DISCH_THEN(MP_TAC o ISPEC `(:real)` o MATCH_MP
1673 (REWRITE_RULE[IMP_CONJ] CARD_EQ_COUNTABLE)) THEN
1674 REWRITE_TAC[UNCOUNTABLE_REAL] THEN ASM_MESON_TAC[CARD_EQ_SYM]);;
1676 let COUNTABLE_IMP_CARD_LT_REAL = prove
1677 (`!s:A->bool. COUNTABLE s ==> s <_c (:real)`,
1678 REWRITE_TAC[GSYM CARD_NOT_LE] THEN
1679 ASM_MESON_TAC[CARD_LE_COUNTABLE; UNCOUNTABLE_REAL]);;
1681 (* ------------------------------------------------------------------------- *)
1682 (* More about cardinality of lists and restricted powersets etc. *)
1683 (* ------------------------------------------------------------------------- *)
1685 let CARD_EQ_FINITE_SUBSETS = prove
1686 (`!s:A->bool. INFINITE(s) ==> {t | t SUBSET s /\ FINITE t} =_c s`,
1687 GEN_TAC THEN DISCH_TAC THEN REWRITE_TAC[GSYM CARD_LE_ANTISYM] THEN
1689 [TRANS_TAC CARD_LE_TRANS `{l:A list | !x. MEM x l ==> x IN s}` THEN
1691 [REWRITE_TAC[LE_C; IN_ELIM_THM] THEN
1692 EXISTS_TAC `set_of_list:A list->(A->bool)` THEN
1693 X_GEN_TAC `t:A->bool` THEN STRIP_TAC THEN
1694 EXISTS_TAC `list_of_set(t:A->bool)` THEN
1695 ASM_SIMP_TAC[MEM_LIST_OF_SET; GSYM SUBSET; SET_OF_LIST_OF_SET];
1696 MATCH_MP_TAC CARD_EQ_IMP_LE THEN
1697 MATCH_MP_TAC CARD_EQ_LIST_GEN THEN ASM_REWRITE_TAC[]];
1698 REWRITE_TAC[le_c] THEN EXISTS_TAC `\x:A. {x}` THEN
1699 REWRITE_TAC[IN_ELIM_THM; FINITE_SING] THEN SET_TAC[]]);;
1701 let CARD_LE_LIST = prove
1702 (`!s:A->bool t:B->bool.
1704 ==> {l | !x. MEM x l ==> x IN s} <=_c {l | !x. MEM x l ==> x IN t}`,
1705 GEN_TAC THEN GEN_TAC THEN REWRITE_TAC[le_c; IN_ELIM_THM] THEN
1706 DISCH_THEN(X_CHOOSE_THEN `f:A->B` STRIP_ASSUME_TAC) THEN
1707 EXISTS_TAC `MAP (f:A->B)` THEN
1708 MATCH_MP_TAC(TAUT `p /\ (p ==> q) ==> p /\ q`) THEN CONJ_TAC THENL
1709 [REWRITE_TAC[MEM_MAP] THEN ASM_MESON_TAC[]; DISCH_TAC] THEN
1710 ONCE_REWRITE_TAC[SWAP_FORALL_THM] THEN
1711 LIST_INDUCT_TAC THEN SIMP_TAC[MAP_EQ_NIL; MAP] THEN
1712 LIST_INDUCT_TAC THEN REWRITE_TAC[MAP; NOT_CONS_NIL; MEM; CONS_11] THEN
1715 let CARD_LE_SUBPOWERSET = prove
1716 (`!s:A->bool t:B->bool.
1717 s <=_c t /\ (!f s. P s ==> Q(IMAGE f s))
1718 ==> {u | u SUBSET s /\ P u} <=_c {v | v SUBSET t /\ Q v}`,
1719 REPEAT GEN_TAC THEN REWRITE_TAC[le_c; IN_ELIM_THM] THEN DISCH_THEN
1720 (CONJUNCTS_THEN2 (X_CHOOSE_THEN `f:A->B` STRIP_ASSUME_TAC) ASSUME_TAC) THEN
1721 EXISTS_TAC `IMAGE (f:A->B)` THEN ASM_SIMP_TAC[] THEN ASM SET_TAC[]);;
1723 let CARD_LE_FINITE_SUBSETS = prove
1724 (`!s:A->bool t:B->bool.
1726 ==> {u | u SUBSET s /\ FINITE u} <=_c {v | v SUBSET t /\ FINITE v}`,
1727 REPEAT STRIP_TAC THEN MATCH_MP_TAC CARD_LE_SUBPOWERSET THEN
1728 ASM_SIMP_TAC[FINITE_IMAGE]);;
1730 let CARD_LE_COUNTABLE_SUBSETS = prove
1731 (`!s:A->bool t:B->bool.
1733 ==> {u | u SUBSET s /\ COUNTABLE u} <=_c {v | v SUBSET t /\ COUNTABLE v}`,
1734 REPEAT STRIP_TAC THEN MATCH_MP_TAC CARD_LE_SUBPOWERSET THEN
1735 ASM_SIMP_TAC[COUNTABLE_IMAGE]);;
1737 let CARD_LE_POWERSET = prove
1738 (`!s:A->bool t:B->bool.
1739 s <=_c t ==> {u | u SUBSET s} <=_c {v | v SUBSET t}`,
1740 REPEAT STRIP_TAC THEN PURE_ONCE_REWRITE_TAC[SET_RULE
1741 `{x | x SUBSET y} = {x | x SUBSET y /\ T}`] THEN
1742 MATCH_MP_TAC CARD_LE_SUBPOWERSET THEN
1745 let COUNTABLE_LIST_GEN = prove
1746 (`!s:A->bool. COUNTABLE s ==> COUNTABLE {l | !x. MEM x l ==> x IN s}`,
1747 GEN_TAC THEN REWRITE_TAC[COUNTABLE; ge_c] THEN
1748 DISCH_THEN(MP_TAC o MATCH_MP CARD_LE_LIST) THEN
1749 MATCH_MP_TAC(REWRITE_RULE[IMP_CONJ_ALT] CARD_LE_TRANS) THEN
1750 MATCH_MP_TAC CARD_EQ_IMP_LE THEN
1751 REWRITE_TAC[IN_UNIV; SET_RULE `{x | T} = UNIV`] THEN
1752 SIMP_TAC[CARD_EQ_LIST; num_INFINITE]);;
1754 let COUNTABLE_LIST = prove
1755 (`COUNTABLE(:A) ==> COUNTABLE(:A list)`,
1756 MP_TAC(ISPEC `(:A)` COUNTABLE_LIST_GEN) THEN
1757 REWRITE_TAC[IN_UNIV; SET_RULE `{x | T} = UNIV`]);;
1759 let COUNTABLE_FINITE_SUBSETS = prove
1760 (`!s:A->bool. COUNTABLE(s) ==> COUNTABLE {t | t SUBSET s /\ FINITE t}`,
1761 GEN_TAC THEN REWRITE_TAC[COUNTABLE; ge_c] THEN
1762 DISCH_THEN(MP_TAC o MATCH_MP CARD_LE_FINITE_SUBSETS) THEN
1763 MATCH_MP_TAC(REWRITE_RULE[IMP_CONJ_ALT] CARD_LE_TRANS) THEN
1764 MATCH_MP_TAC CARD_EQ_IMP_LE THEN
1765 REWRITE_TAC[IN_UNIV; SET_RULE `{x | T} = UNIV`] THEN
1766 SIMP_TAC[CARD_EQ_FINITE_SUBSETS; num_INFINITE]);;
1768 let CARD_EQ_REAL_SEQUENCES = prove
1769 (`(:num->real) =_c (:real)`,
1770 TRANS_TAC CARD_EQ_TRANS `(:num->num->bool)` THEN
1771 ASM_SIMP_TAC[CARD_FUNSPACE_CONG; CARD_EQ_REFL; CARD_EQ_REAL] THEN
1772 TRANS_TAC CARD_EQ_TRANS `(:num#num->bool)` THEN
1773 ASM_SIMP_TAC[CARD_FUNSPACE_CURRY] THEN
1774 TRANS_TAC CARD_EQ_TRANS `(:num->bool)` THEN
1775 ASM_SIMP_TAC[CARD_FUNSPACE_CONG; CARD_EQ_REFL;
1776 ONCE_REWRITE_RULE[CARD_EQ_SYM] CARD_EQ_REAL;
1777 REWRITE_RULE[MUL_C_UNIV] CARD_SQUARE_NUM]);;
1779 let CARD_EQ_COUNTABLE_SUBSETS_REAL = prove
1780 (`{s:real->bool | COUNTABLE s} =_c (:real)`,
1781 REWRITE_TAC[GSYM CARD_LE_ANTISYM] THEN CONJ_TAC THENL
1782 [TRANS_TAC CARD_LE_TRANS
1783 `{{}:real->bool} +_c {s:real->bool | COUNTABLE s /\ ~(s = {})}` THEN
1785 [W(MP_TAC o PART_MATCH rand UNION_LE_ADD_C o rand o snd) THEN
1786 MATCH_MP_TAC(REWRITE_RULE[IMP_CONJ] CARD_LE_TRANS) THEN
1787 MATCH_MP_TAC(MESON[CARD_LE_REFL] `s = t ==> s <=_c t`) THEN
1788 ONCE_REWRITE_TAC[EXTENSION] THEN
1789 REWRITE_TAC[IN_ELIM_THM; IN_UNION; IN_SING] THEN
1790 MESON_TAC[COUNTABLE_EMPTY];
1792 TRANS_TAC CARD_LE_TRANS `{{}:real->bool} +_c (:real)` THEN CONJ_TAC THENL
1793 [MATCH_MP_TAC CARD_LE_ADD THEN
1794 REWRITE_TAC[CARD_LE_REFL] THEN
1795 TRANS_TAC CARD_LE_TRANS `(:num->real)` THEN
1796 ASM_SIMP_TAC[CARD_EQ_REAL_SEQUENCES; CARD_EQ_IMP_LE] THEN
1797 REWRITE_TAC[LE_C] THEN EXISTS_TAC `\f:num->real. IMAGE f (:num)` THEN
1798 REWRITE_TAC[IN_UNIV; IN_ELIM_THM] THEN
1799 MESON_TAC[COUNTABLE_AS_IMAGE];
1800 MATCH_MP_TAC CARD_ADD_ABSORB_LE THEN
1801 SIMP_TAC[real_INFINITE; le_c; IN_UNIV; IN_SING]];
1802 REWRITE_TAC[le_c] THEN EXISTS_TAC `\x:real. {x}` THEN
1803 REWRITE_TAC[IN_UNIV; COUNTABLE_SING; IN_ELIM_THM] THEN SET_TAC[]]);;