1 (* ========================================================================= *)
2 (* Theory of lists, plus characters and strings as lists of characters. *)
4 (* John Harrison, University of Cambridge Computer Laboratory *)
6 (* (c) Copyright, University of Cambridge 1998 *)
7 (* (c) Copyright, John Harrison 1998-2007 *)
8 (* ========================================================================= *)
10 needs "ind_types.ml";;
12 (* ------------------------------------------------------------------------- *)
13 (* Standard tactic for list induction using MATCH_MP_TAC list_INDUCT *)
14 (* ------------------------------------------------------------------------- *)
17 let list_INDUCT = prove
18 (`!P:(A)list->bool. P [] /\ (!h t. P t ==> P (CONS h t)) ==> !l. P l`,
19 MATCH_ACCEPT_TAC list_INDUCT) in
20 MATCH_MP_TAC list_INDUCT THEN
21 CONJ_TAC THENL [ALL_TAC; GEN_TAC THEN GEN_TAC THEN DISCH_TAC];;
23 (* ------------------------------------------------------------------------- *)
24 (* Basic definitions. *)
25 (* ------------------------------------------------------------------------- *)
27 let HD = new_recursive_definition list_RECURSION
28 `HD(CONS (h:A) t) = h`;;
30 let TL = new_recursive_definition list_RECURSION
31 `TL(CONS (h:A) t) = t`;;
33 let APPEND = new_recursive_definition list_RECURSION
34 `(!l:(A)list. APPEND [] l = l) /\
35 (!h t l. APPEND (CONS h t) l = CONS h (APPEND t l))`;;
37 let REVERSE = new_recursive_definition list_RECURSION
39 (REVERSE (CONS (x:A) l) = APPEND (REVERSE l) [x])`;;
41 let LENGTH = new_recursive_definition list_RECURSION
43 (!h:A. !t. LENGTH (CONS h t) = SUC (LENGTH t))`;;
45 let MAP = new_recursive_definition list_RECURSION
46 `(!f:A->B. MAP f NIL = NIL) /\
47 (!f h t. MAP f (CONS h t) = CONS (f h) (MAP f t))`;;
49 let LAST = new_recursive_definition list_RECURSION
50 `LAST (CONS (h:A) t) = if t = [] then h else LAST t`;;
52 let BUTLAST = new_recursive_definition list_RECURSION
54 (BUTLAST (CONS h t) = if t = [] then [] else CONS h (BUTLAST t))`;;
56 let REPLICATE = new_recursive_definition num_RECURSION
57 `(REPLICATE 0 x = []) /\
58 (REPLICATE (SUC n) x = CONS x (REPLICATE n x))`;;
60 let NULL = new_recursive_definition list_RECURSION
62 (NULL (CONS h t) = F)`;;
64 let ALL = new_recursive_definition list_RECURSION
66 (ALL P (CONS h t) <=> P h /\ ALL P t)`;;
68 let EX = new_recursive_definition list_RECURSION
70 (EX P (CONS h t) <=> P h \/ EX P t)`;;
72 let ITLIST = new_recursive_definition list_RECURSION
73 `(ITLIST f [] b = b) /\
74 (ITLIST f (CONS h t) b = f h (ITLIST f t b))`;;
76 let MEM = new_recursive_definition list_RECURSION
78 (MEM x (CONS h t) <=> (x = h) \/ MEM x t)`;;
80 let ALL2_DEF = new_recursive_definition list_RECURSION
81 `(ALL2 P [] l2 <=> (l2 = [])) /\
82 (ALL2 P (CONS h1 t1) l2 <=>
84 else P h1 (HD l2) /\ ALL2 P t1 (TL l2))`;;
87 (`(ALL2 P [] [] <=> T) /\
88 (ALL2 P (CONS h1 t1) [] <=> F) /\
89 (ALL2 P [] (CONS h2 t2) <=> F) /\
90 (ALL2 P (CONS h1 t1) (CONS h2 t2) <=> P h1 h2 /\ ALL2 P t1 t2)`,
91 REWRITE_TAC[distinctness "list"; ALL2_DEF; HD; TL]);;
93 let MAP2_DEF = new_recursive_definition list_RECURSION
94 `(MAP2 f [] l = []) /\
95 (MAP2 f (CONS h1 t1) l = CONS (f h1 (HD l)) (MAP2 f t1 (TL l)))`;;
98 (`(MAP2 f [] [] = []) /\
99 (MAP2 f (CONS h1 t1) (CONS h2 t2) = CONS (f h1 h2) (MAP2 f t1 t2))`,
100 REWRITE_TAC[MAP2_DEF; HD; TL]);;
102 let EL = new_recursive_definition num_RECURSION
104 (EL (SUC n) l = EL n (TL l))`;;
106 let FILTER = new_recursive_definition list_RECURSION
107 `(FILTER P [] = []) /\
108 (FILTER P (CONS h t) = if P h then CONS h (FILTER P t) else FILTER P t)`;;
110 let ASSOC = new_recursive_definition list_RECURSION
111 `ASSOC a (CONS h t) = if FST h = a then SND h else ASSOC a t`;;
113 let ITLIST2_DEF = new_recursive_definition list_RECURSION
114 `(ITLIST2 f [] l2 b = b) /\
115 (ITLIST2 f (CONS h1 t1) l2 b = f h1 (HD l2) (ITLIST2 f t1 (TL l2) b))`;;
118 (`(ITLIST2 f [] [] b = b) /\
119 (ITLIST2 f (CONS h1 t1) (CONS h2 t2) b = f h1 h2 (ITLIST2 f t1 t2 b))`,
120 REWRITE_TAC[ITLIST2_DEF; HD; TL]);;
122 let ZIP_DEF = new_recursive_definition list_RECURSION
124 (ZIP (CONS h1 t1) l2 = CONS (h1,HD l2) (ZIP t1 (TL l2)))`;;
127 (`(ZIP [] [] = []) /\
128 (ZIP (CONS h1 t1) (CONS h2 t2) = CONS (h1,h2) (ZIP t1 t2))`,
129 REWRITE_TAC[ZIP_DEF; HD; TL]);;
131 (* ------------------------------------------------------------------------- *)
132 (* Various trivial theorems. *)
133 (* ------------------------------------------------------------------------- *)
135 let NOT_CONS_NIL = prove
136 (`!(h:A) t. ~(CONS h t = [])`,
137 REWRITE_TAC[distinctness "list"]);;
139 let LAST_CLAUSES = prove
140 (`(LAST [h:A] = h) /\
141 (LAST (CONS h (CONS k t)) = LAST (CONS k t))`,
142 REWRITE_TAC[LAST; NOT_CONS_NIL]);;
144 let APPEND_NIL = prove
145 (`!l:A list. APPEND l [] = l`,
146 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[APPEND]);;
148 let APPEND_ASSOC = prove
149 (`!(l:A list) m n. APPEND l (APPEND m n) = APPEND (APPEND l m) n`,
150 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[APPEND]);;
152 let REVERSE_APPEND = prove
153 (`!(l:A list) m. REVERSE (APPEND l m) = APPEND (REVERSE m) (REVERSE l)`,
155 ASM_REWRITE_TAC[APPEND; REVERSE; APPEND_NIL; APPEND_ASSOC]);;
157 let REVERSE_REVERSE = prove
158 (`!l:A list. REVERSE(REVERSE l) = l`,
159 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[REVERSE; REVERSE_APPEND; APPEND]);;
162 (`!(h1:A) h2 t1 t2. (CONS h1 t1 = CONS h2 t2) <=> (h1 = h2) /\ (t1 = t2)`,
163 REWRITE_TAC[injectivity "list"]);;
165 let list_CASES = prove
166 (`!l:(A)list. (l = []) \/ ?h t. l = CONS h t`,
167 LIST_INDUCT_TAC THEN REWRITE_TAC[CONS_11; NOT_CONS_NIL] THEN
170 let LENGTH_APPEND = prove
171 (`!(l:A list) m. LENGTH(APPEND l m) = LENGTH l + LENGTH m`,
172 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[APPEND; LENGTH; ADD_CLAUSES]);;
174 let MAP_APPEND = prove
175 (`!f:A->B. !l1 l2. MAP f (APPEND l1 l2) = APPEND (MAP f l1) (MAP f l2)`,
176 GEN_TAC THEN LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[MAP; APPEND]);;
178 let LENGTH_MAP = prove
179 (`!l. !f:A->B. LENGTH (MAP f l) = LENGTH l`,
180 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[MAP; LENGTH]);;
182 let LENGTH_EQ_NIL = prove
183 (`!l:A list. (LENGTH l = 0) <=> (l = [])`,
184 LIST_INDUCT_TAC THEN REWRITE_TAC[LENGTH; NOT_CONS_NIL; NOT_SUC]);;
186 let LENGTH_EQ_CONS = prove
187 (`!l n. (LENGTH l = SUC n) <=> ?h t. (l = CONS h t) /\ (LENGTH t = n)`,
188 LIST_INDUCT_TAC THEN REWRITE_TAC[LENGTH; NOT_SUC; NOT_CONS_NIL] THEN
189 ASM_REWRITE_TAC[SUC_INJ; CONS_11] THEN MESON_TAC[]);;
192 (`!f:A->B. !g:B->C. !l. MAP (g o f) l = MAP g (MAP f l)`,
193 GEN_TAC THEN GEN_TAC THEN LIST_INDUCT_TAC THEN
194 ASM_REWRITE_TAC[MAP; o_THM]);;
197 (`!f g l. ALL (\x. f x = g x) l ==> (MAP f l = MAP g l)`,
198 GEN_TAC THEN GEN_TAC THEN LIST_INDUCT_TAC THEN
199 REWRITE_TAC[MAP; ALL] THEN ASM_MESON_TAC[]);;
202 (`!P Q l. (!x. MEM x l /\ P x ==> Q x) /\ ALL P l ==> ALL Q l`,
203 GEN_TAC THEN GEN_TAC THEN LIST_INDUCT_TAC THEN
204 REWRITE_TAC[MEM; ALL] THEN ASM_MESON_TAC[]);;
207 (`!P l. ~(EX P l) <=> ALL (\x. ~(P x)) l`,
208 GEN_TAC THEN LIST_INDUCT_TAC THEN
209 ASM_REWRITE_TAC[EX; ALL; DE_MORGAN_THM]);;
212 (`!P l. ~(ALL P l) <=> EX (\x. ~(P x)) l`,
213 GEN_TAC THEN LIST_INDUCT_TAC THEN
214 ASM_REWRITE_TAC[EX; ALL; DE_MORGAN_THM]);;
217 (`!P f l. ALL P (MAP f l) <=> ALL (P o f) l`,
218 GEN_TAC THEN GEN_TAC THEN LIST_INDUCT_TAC THEN
219 ASM_REWRITE_TAC[ALL; MAP; o_THM]);;
222 (`!l. ALL (\x. T) l`,
223 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[ALL]);;
225 let MAP_EQ_ALL2 = prove
226 (`!l m. ALL2 (\x y. f x = f y) l m ==> (MAP f l = MAP f m)`,
227 REPEAT LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[MAP; ALL2; CONS_11] THEN
231 (`!P f l. ALL2 P (MAP f l) l <=> ALL (\a. P (f a) a) l`,
232 GEN_TAC THEN GEN_TAC THEN
233 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[ALL2; MAP; ALL]);;
235 let MAP_EQ_DEGEN = prove
236 (`!l f. ALL (\x. f(x) = x) l ==> (MAP f l = l)`,
237 LIST_INDUCT_TAC THEN REWRITE_TAC[ALL; MAP; CONS_11] THEN
238 REPEAT STRIP_TAC THEN ASM_REWRITE_TAC[] THEN
239 FIRST_ASSUM MATCH_MP_TAC THEN ASM_REWRITE_TAC[]);;
241 let ALL2_AND_RIGHT = prove
242 (`!l m P Q. ALL2 (\x y. P x /\ Q x y) l m <=> ALL P l /\ ALL2 Q l m`,
243 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[ALL; ALL2] THEN
244 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[ALL; ALL2] THEN
245 REWRITE_TAC[CONJ_ACI]);;
247 let ITLIST_APPEND = prove
248 (`!f a l1 l2. ITLIST f (APPEND l1 l2) a = ITLIST f l1 (ITLIST f l2 a)`,
249 GEN_TAC THEN GEN_TAC THEN LIST_INDUCT_TAC THEN
250 ASM_REWRITE_TAC[ITLIST; APPEND]);;
252 let ITLIST_EXTRA = prove
253 (`!l. ITLIST f (APPEND l [a]) b = ITLIST f l (f a b)`,
254 REWRITE_TAC[ITLIST_APPEND; ITLIST]);;
257 (`!P Q l. ALL (\x. P x ==> Q x) l /\ ALL P l ==> ALL Q l`,
258 GEN_TAC THEN GEN_TAC THEN LIST_INDUCT_TAC THEN
259 REWRITE_TAC[ALL] THEN ASM_MESON_TAC[]);;
262 (`!l. ALL P l /\ ALL Q l <=> ALL (\x. P x /\ Q x) l`,
263 CONV_TAC(ONCE_DEPTH_CONV SYM_CONV) THEN
264 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[ALL; CONJ_ACI]);;
267 (`!P Q l. (!x. MEM x l /\ P x ==> Q x) /\ EX P l ==> EX Q l`,
268 GEN_TAC THEN GEN_TAC THEN LIST_INDUCT_TAC THEN
269 REWRITE_TAC[MEM; EX] THEN ASM_MESON_TAC[]);;
272 (`!P l. (!x. MEM x l ==> P x) <=> ALL P l`,
273 GEN_TAC THEN LIST_INDUCT_TAC THEN REWRITE_TAC[ALL; MEM] THEN
276 let LENGTH_REPLICATE = prove
277 (`!n x. LENGTH(REPLICATE n x) = n`,
278 INDUCT_TAC THEN ASM_REWRITE_TAC[LENGTH; REPLICATE]);;
281 (`!P f l. EX P (MAP f l) <=> EX (P o f) l`,
282 GEN_TAC THEN GEN_TAC THEN
283 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[MAP; EX; o_THM]);;
285 let EXISTS_EX = prove
286 (`!P l. (?x. EX (P x) l) <=> EX (\s. ?x. P x s) l`,
287 GEN_TAC THEN LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[EX] THEN
290 let FORALL_ALL = prove
291 (`!P l. (!x. ALL (P x) l) <=> ALL (\s. !x. P x s) l`,
292 GEN_TAC THEN LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[ALL] THEN
295 let MEM_APPEND = prove
296 (`!x l1 l2. MEM x (APPEND l1 l2) <=> MEM x l1 \/ MEM x l2`,
297 GEN_TAC THEN LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[MEM; APPEND; DISJ_ACI]);;
300 (`!f y l. MEM y (MAP f l) <=> ?x. MEM x l /\ (y = f x)`,
301 GEN_TAC THEN GEN_TAC THEN LIST_INDUCT_TAC THEN
302 ASM_REWRITE_TAC[MEM; MAP] THEN MESON_TAC[]);;
304 let FILTER_APPEND = prove
305 (`!P l1 l2. FILTER P (APPEND l1 l2) = APPEND (FILTER P l1) (FILTER P l2)`,
306 GEN_TAC THEN LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[FILTER; APPEND] THEN
307 GEN_TAC THEN COND_CASES_TAC THEN ASM_REWRITE_TAC[APPEND]);;
309 let FILTER_MAP = prove
310 (`!P f l. FILTER P (MAP f l) = MAP f (FILTER (P o f) l)`,
311 GEN_TAC THEN GEN_TAC THEN LIST_INDUCT_TAC THEN
312 ASM_REWRITE_TAC[MAP; FILTER; o_THM] THEN COND_CASES_TAC THEN
315 let MEM_FILTER = prove
316 (`!P l x. MEM x (FILTER P l) <=> P x /\ MEM x l`,
317 GEN_TAC THEN LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[MEM; FILTER] THEN
318 GEN_TAC THEN COND_CASES_TAC THEN ASM_REWRITE_TAC[MEM] THEN
322 (`!P l. (?x. P x /\ MEM x l) <=> EX P l`,
323 GEN_TAC THEN LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[EX; MEM] THEN
326 let MAP_FST_ZIP = prove
327 (`!l1 l2. (LENGTH l1 = LENGTH l2) ==> (MAP FST (ZIP l1 l2) = l1)`,
328 LIST_INDUCT_TAC THEN LIST_INDUCT_TAC THEN
329 ASM_SIMP_TAC[LENGTH; SUC_INJ; MAP; FST; ZIP; NOT_SUC]);;
331 let MAP_SND_ZIP = prove
332 (`!l1 l2. (LENGTH l1 = LENGTH l2) ==> (MAP SND (ZIP l1 l2) = l2)`,
333 LIST_INDUCT_TAC THEN LIST_INDUCT_TAC THEN
334 ASM_SIMP_TAC[LENGTH; SUC_INJ; MAP; FST; ZIP; NOT_SUC]);;
336 let MEM_ASSOC = prove
337 (`!l x. MEM (x,ASSOC x l) l <=> MEM x (MAP FST l)`,
338 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[MEM; MAP; ASSOC] THEN
339 GEN_TAC THEN COND_CASES_TAC THEN ASM_REWRITE_TAC[] THEN
340 ASM_MESON_TAC[PAIR; FST]);;
342 let ALL_APPEND = prove
343 (`!P l1 l2. ALL P (APPEND l1 l2) <=> ALL P l1 /\ ALL P l2`,
344 GEN_TAC THEN LIST_INDUCT_TAC THEN
345 ASM_REWRITE_TAC[ALL; APPEND; GSYM CONJ_ASSOC]);;
348 (`!l n. n < LENGTH l ==> MEM (EL n l) l`,
349 LIST_INDUCT_TAC THEN REWRITE_TAC[MEM; CONJUNCT1 LT; LENGTH] THEN
350 INDUCT_TAC THEN ASM_SIMP_TAC[EL; HD; LT_SUC; TL]);;
352 let MEM_EXISTS_EL = prove
353 (`!l x. MEM x l <=> ?i. i < LENGTH l /\ x = EL i l`,
354 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[LENGTH; EL; MEM; CONJUNCT1 LT] THEN
355 GEN_TAC THEN GEN_REWRITE_TAC RAND_CONV
356 [MESON[num_CASES] `(?i. P i) <=> P 0 \/ (?i. P(SUC i))`] THEN
357 REWRITE_TAC[LT_SUC; LT_0; EL; HD; TL]);;
360 (`!P l. (!i. i < LENGTH l ==> P (EL i l)) <=> ALL P l`,
361 REWRITE_TAC[GSYM ALL_MEM; MEM_EXISTS_EL] THEN MESON_TAC[]);;
363 let ALL2_MAP2 = prove
364 (`!l m. ALL2 P (MAP f l) (MAP g m) = ALL2 (\x y. P (f x) (g y)) l m`,
365 LIST_INDUCT_TAC THEN LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[ALL2; MAP]);;
368 (`!P Q l m. ALL2 P l m /\ ALL2 Q l m <=> ALL2 (\x y. P x y /\ Q x y) l m`,
369 GEN_TAC THEN GEN_TAC THEN CONV_TAC(ONCE_DEPTH_CONV SYM_CONV) THEN
370 LIST_INDUCT_TAC THEN LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[ALL2] THEN
371 REWRITE_TAC[CONJ_ACI]);;
374 (`!P l. ALL2 P l l <=> ALL (\x. P x x) l`,
375 GEN_TAC THEN LIST_INDUCT_TAC THEN
376 ASM_REWRITE_TAC[ALL2; ALL]);;
378 let APPEND_EQ_NIL = prove
379 (`!l m. (APPEND l m = []) <=> (l = []) /\ (m = [])`,
380 REWRITE_TAC[GSYM LENGTH_EQ_NIL; LENGTH_APPEND; ADD_EQ_0]);;
382 let LENGTH_MAP2 = prove
383 (`!f l m. (LENGTH l = LENGTH m) ==> (LENGTH(MAP2 f l m) = LENGTH m)`,
384 GEN_TAC THEN LIST_INDUCT_TAC THEN LIST_INDUCT_TAC THEN
385 ASM_SIMP_TAC[LENGTH; NOT_CONS_NIL; NOT_SUC; MAP2; SUC_INJ]);;
387 let MAP_EQ_NIL = prove
388 (`!f l. MAP f l = [] <=> l = []`,
389 GEN_TAC THEN LIST_INDUCT_TAC THEN REWRITE_TAC[MAP; NOT_CONS_NIL]);;
391 let INJECTIVE_MAP = prove
392 (`!f:A->B. (!l m. MAP f l = MAP f m ==> l = m) <=>
393 (!x y. f x = f y ==> x = y)`,
394 GEN_TAC THEN EQ_TAC THEN DISCH_TAC THENL
395 [MAP_EVERY X_GEN_TAC [`x:A`; `y:A`] THEN DISCH_TAC THEN
396 FIRST_X_ASSUM(MP_TAC o SPECL [`[x:A]`; `[y:A]`]) THEN
397 ASM_REWRITE_TAC[MAP; CONS_11];
398 REPEAT LIST_INDUCT_TAC THEN ASM_SIMP_TAC[MAP; NOT_CONS_NIL; CONS_11] THEN
401 let SURJECTIVE_MAP = prove
402 (`!f:A->B. (!m. ?l. MAP f l = m) <=> (!y. ?x. f x = y)`,
403 GEN_TAC THEN EQ_TAC THEN DISCH_TAC THENL
404 [X_GEN_TAC `y:B` THEN FIRST_X_ASSUM(MP_TAC o SPEC `[y:B]`) THEN
405 REWRITE_TAC[LEFT_IMP_EXISTS_THM] THEN
406 LIST_INDUCT_TAC THEN REWRITE_TAC[MAP; CONS_11; NOT_CONS_NIL; MAP_EQ_NIL];
407 MATCH_MP_TAC list_INDUCT] THEN
408 ASM_MESON_TAC[MAP]);;
411 (`!l. MAP (\x. x) l = l`,
412 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[MAP]);;
416 REWRITE_TAC[FUN_EQ_THM; I_DEF; MAP_ID]);;
418 let APPEND_BUTLAST_LAST = prove
419 (`!l. ~(l = []) ==> APPEND (BUTLAST l) [LAST l] = l`,
420 LIST_INDUCT_TAC THEN REWRITE_TAC[LAST; BUTLAST; NOT_CONS_NIL] THEN
421 COND_CASES_TAC THEN ASM_SIMP_TAC[APPEND]);;
423 let LAST_APPEND = prove
424 (`!p q. LAST(APPEND p q) = if q = [] then LAST p else LAST q`,
425 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[APPEND; LAST; APPEND_EQ_NIL] THEN
428 let LENGTH_TL = prove
429 (`!l. ~(l = []) ==> LENGTH(TL l) = LENGTH l - 1`,
430 LIST_INDUCT_TAC THEN REWRITE_TAC[LENGTH; TL; ARITH; SUC_SUB1]);;
432 let EL_APPEND = prove
433 (`!k l m. EL k (APPEND l m) = if k < LENGTH l then EL k l
434 else EL (k - LENGTH l) m`,
435 INDUCT_TAC THEN REWRITE_TAC[EL] THEN
437 REWRITE_TAC[HD; APPEND; LENGTH; SUB_0; EL; LT_0; CONJUNCT1 LT] THEN
438 ASM_REWRITE_TAC[TL; LT_SUC; SUB_SUC]);;
441 (`!n. EL n (TL l) = EL (n + 1) l`,
442 REWRITE_TAC[GSYM ADD1; EL]);;
445 (`!n h t. EL n (CONS h t) = if n = 0 then h else EL (n - 1) t`,
446 INDUCT_TAC THEN REWRITE_TAC[EL; HD; TL; NOT_SUC; SUC_SUB1]);;
449 (`!l. ~(l = []) ==> LAST l = EL (LENGTH l - 1) l`,
450 LIST_INDUCT_TAC THEN REWRITE_TAC[LAST; LENGTH; SUC_SUB1] THEN
451 DISCH_TAC THEN COND_CASES_TAC THEN
452 ASM_SIMP_TAC[LENGTH; EL; HD; EL_CONS; LENGTH_EQ_NIL]);;
454 let HD_APPEND = prove
455 (`!l m:A list. HD(APPEND l m) = if l = [] then HD m else HD l`,
456 LIST_INDUCT_TAC THEN REWRITE_TAC[HD; APPEND; NOT_CONS_NIL]);;
458 let CONS_HD_TL = prove
459 (`!l. ~(l = []) ==> l = CONS (HD l) (TL l)`,
460 LIST_INDUCT_TAC THEN REWRITE_TAC[NOT_CONS_NIL;HD;TL]);;
463 (`!f n l. n < LENGTH l ==> EL n (MAP f l) = f(EL n l)`,
464 GEN_TAC THEN INDUCT_TAC THEN LIST_INDUCT_TAC THEN
465 ASM_REWRITE_TAC[LENGTH; CONJUNCT1 LT; LT_0; EL; HD; TL; MAP; LT_SUC]);;
467 let MAP_REVERSE = prove
468 (`!f l. REVERSE(MAP f l) = MAP f (REVERSE l)`,
469 GEN_TAC THEN LIST_INDUCT_TAC THEN
470 ASM_REWRITE_TAC[MAP; REVERSE; MAP_APPEND]);;
472 let ALL_FILTER = prove
473 (`!P Q l:A list. ALL P (FILTER Q l) <=> ALL (\x. Q x ==> P x) l`,
474 GEN_TAC THEN GEN_TAC THEN
475 LIST_INDUCT_TAC THEN REWRITE_TAC[ALL; FILTER] THEN
476 COND_CASES_TAC THEN ASM_REWRITE_TAC[ALL]);;
478 let APPEND_SING = prove
479 (`!h t. APPEND [h] t = CONS h t`,
480 REWRITE_TAC[APPEND]);;
482 let MEM_APPEND_DECOMPOSE_LEFT = prove
483 (`!x:A l. MEM x l <=> ?l1 l2. ~(MEM x l1) /\ l = APPEND l1 (CONS x l2)`,
484 REWRITE_TAC[TAUT `(p <=> q) <=> (p ==> q) /\ (q ==> p)`] THEN
485 SIMP_TAC[LEFT_IMP_EXISTS_THM; MEM_APPEND; MEM] THEN X_GEN_TAC `x:A` THEN
486 MATCH_MP_TAC list_INDUCT THEN REWRITE_TAC[MEM] THEN
487 MAP_EVERY X_GEN_TAC [`y:A`; `l:A list`] THEN
488 ASM_CASES_TAC `x:A = y` THEN ASM_MESON_TAC[MEM; APPEND]);;
490 let MEM_APPEND_DECOMPOSE = prove
491 (`!x:A l. MEM x l <=> ?l1 l2. l = APPEND l1 (CONS x l2)`,
492 REWRITE_TAC[TAUT `(p <=> q) <=> (p ==> q) /\ (q ==> p)`] THEN
493 SIMP_TAC[LEFT_IMP_EXISTS_THM; MEM_APPEND; MEM] THEN
494 ONCE_REWRITE_TAC[MEM_APPEND_DECOMPOSE_LEFT] THEN MESON_TAC[]);;
496 (* ------------------------------------------------------------------------- *)
498 (* ------------------------------------------------------------------------- *)
501 try let cons = mk_const("CONS",[type_of h,aty]) in
502 mk_comb(mk_comb(cons,h),t)
503 with Failure _ -> failwith "mk_cons";;
505 let mk_list (tms,ty) =
506 try let nil = mk_const("NIL",[ty,aty]) in
507 if tms = [] then nil else
508 let cons = mk_const("CONS",[ty,aty]) in
509 itlist (mk_binop cons) tms nil
510 with Failure _ -> failwith "mk_list";;
513 try mk_list(tms,type_of(hd tms))
514 with Failure _ -> failwith "mk_flist";;
516 (* ------------------------------------------------------------------------- *)
517 (* Extra monotonicity theorems for inductive definitions. *)
518 (* ------------------------------------------------------------------------- *)
521 (`(!x:A. P x ==> Q x) ==> ALL P l ==> ALL Q l`,
522 DISCH_TAC THEN SPEC_TAC(`l:A list`,`l:A list`) THEN
523 LIST_INDUCT_TAC THEN ASM_REWRITE_TAC[ALL] THEN ASM_MESON_TAC[]);;
525 let MONO_ALL2 = prove
526 (`(!x y. (P:A->B->bool) x y ==> Q x y) ==> ALL2 P l l' ==> ALL2 Q l l'`,
528 SPEC_TAC(`l':B list`,`l':B list`) THEN SPEC_TAC(`l:A list`,`l:A list`) THEN
529 LIST_INDUCT_TAC THEN REWRITE_TAC[ALL2_DEF] THEN
530 GEN_TAC THEN COND_CASES_TAC THEN REWRITE_TAC[] THEN ASM_MESON_TAC[]);;
532 monotonicity_theorems := [MONO_ALL; MONO_ALL2] @ !monotonicity_theorems;;
534 (* ------------------------------------------------------------------------- *)
535 (* Apply a conversion down a list. *)
536 (* ------------------------------------------------------------------------- *)
538 let rec LIST_CONV conv tm =
540 COMB2_CONV (RAND_CONV conv) (LIST_CONV conv) tm
541 else if fst(dest_const tm) = "NIL" then REFL tm
542 else failwith "LIST_CONV";;
544 (* ------------------------------------------------------------------------- *)
545 (* Type of characters, like the HOL88 "ascii" type. *)
546 (* ------------------------------------------------------------------------- *)
548 let char_INDUCT,char_RECURSION = define_type
549 "char = ASCII bool bool bool bool bool bool bool bool";;
551 new_type_abbrev("string",`:char list`);;