summary |
shortlog |
changelog |
graph |
tags |
branches |
files |
changeset |
file |
revisions |
annotate |
diff |
raw

src/HOL/Library/Sublist.thy

author | eberlm <eberlm@in.tum.de> |

Mon May 29 16:40:56 2017 +0200 (2017-05-29) | |

changeset 65957 | 558ba6b37f5c |

parent 65956 | 639eb3617a86 |

child 67091 | 1393c2340eec |

permissions | -rw-r--r-- |

Tuned Library/Sublist.thy

1 (* Title: HOL/Library/Sublist.thy

2 Author: Tobias Nipkow and Markus Wenzel, TU München

3 Author: Christian Sternagel, JAIST

4 Author: Manuel Eberl, TU München

5 *)

7 section \<open>List prefixes, suffixes, and homeomorphic embedding\<close>

9 theory Sublist

10 imports Main

11 begin

13 subsection \<open>Prefix order on lists\<close>

15 definition prefix :: "'a list \<Rightarrow> 'a list \<Rightarrow> bool"

16 where "prefix xs ys \<longleftrightarrow> (\<exists>zs. ys = xs @ zs)"

18 definition strict_prefix :: "'a list \<Rightarrow> 'a list \<Rightarrow> bool"

19 where "strict_prefix xs ys \<longleftrightarrow> prefix xs ys \<and> xs \<noteq> ys"

21 interpretation prefix_order: order prefix strict_prefix

22 by standard (auto simp: prefix_def strict_prefix_def)

24 interpretation prefix_bot: order_bot Nil prefix strict_prefix

25 by standard (simp add: prefix_def)

27 lemma prefixI [intro?]: "ys = xs @ zs \<Longrightarrow> prefix xs ys"

28 unfolding prefix_def by blast

30 lemma prefixE [elim?]:

31 assumes "prefix xs ys"

32 obtains zs where "ys = xs @ zs"

33 using assms unfolding prefix_def by blast

35 lemma strict_prefixI' [intro?]: "ys = xs @ z # zs \<Longrightarrow> strict_prefix xs ys"

36 unfolding strict_prefix_def prefix_def by blast

38 lemma strict_prefixE' [elim?]:

39 assumes "strict_prefix xs ys"

40 obtains z zs where "ys = xs @ z # zs"

41 proof -

42 from \<open>strict_prefix xs ys\<close> obtain us where "ys = xs @ us" and "xs \<noteq> ys"

43 unfolding strict_prefix_def prefix_def by blast

44 with that show ?thesis by (auto simp add: neq_Nil_conv)

45 qed

47 (* FIXME rm *)

48 lemma strict_prefixI [intro?]: "prefix xs ys \<Longrightarrow> xs \<noteq> ys \<Longrightarrow> strict_prefix xs ys"

49 by(fact prefix_order.le_neq_trans)

51 lemma strict_prefixE [elim?]:

52 fixes xs ys :: "'a list"

53 assumes "strict_prefix xs ys"

54 obtains "prefix xs ys" and "xs \<noteq> ys"

55 using assms unfolding strict_prefix_def by blast

58 subsection \<open>Basic properties of prefixes\<close>

60 (* FIXME rm *)

61 theorem Nil_prefix [simp]: "prefix [] xs"

62 by (fact prefix_bot.bot_least)

64 (* FIXME rm *)

65 theorem prefix_Nil [simp]: "(prefix xs []) = (xs = [])"

66 by (fact prefix_bot.bot_unique)

68 lemma prefix_snoc [simp]: "prefix xs (ys @ [y]) \<longleftrightarrow> xs = ys @ [y] \<or> prefix xs ys"

69 proof

70 assume "prefix xs (ys @ [y])"

71 then obtain zs where zs: "ys @ [y] = xs @ zs" ..

72 show "xs = ys @ [y] \<or> prefix xs ys"

73 by (metis append_Nil2 butlast_append butlast_snoc prefixI zs)

74 next

75 assume "xs = ys @ [y] \<or> prefix xs ys"

76 then show "prefix xs (ys @ [y])"

77 by (metis prefix_order.eq_iff prefix_order.order_trans prefixI)

78 qed

80 lemma Cons_prefix_Cons [simp]: "prefix (x # xs) (y # ys) = (x = y \<and> prefix xs ys)"

81 by (auto simp add: prefix_def)

83 lemma prefix_code [code]:

84 "prefix [] xs \<longleftrightarrow> True"

85 "prefix (x # xs) [] \<longleftrightarrow> False"

86 "prefix (x # xs) (y # ys) \<longleftrightarrow> x = y \<and> prefix xs ys"

87 by simp_all

89 lemma same_prefix_prefix [simp]: "prefix (xs @ ys) (xs @ zs) = prefix ys zs"

90 by (induct xs) simp_all

92 lemma same_prefix_nil [simp]: "prefix (xs @ ys) xs = (ys = [])"

93 by (metis append_Nil2 append_self_conv prefix_order.eq_iff prefixI)

95 lemma prefix_prefix [simp]: "prefix xs ys \<Longrightarrow> prefix xs (ys @ zs)"

96 unfolding prefix_def by fastforce

98 lemma append_prefixD: "prefix (xs @ ys) zs \<Longrightarrow> prefix xs zs"

99 by (auto simp add: prefix_def)

101 theorem prefix_Cons: "prefix xs (y # ys) = (xs = [] \<or> (\<exists>zs. xs = y # zs \<and> prefix zs ys))"

102 by (cases xs) (auto simp add: prefix_def)

104 theorem prefix_append:

105 "prefix xs (ys @ zs) = (prefix xs ys \<or> (\<exists>us. xs = ys @ us \<and> prefix us zs))"

106 apply (induct zs rule: rev_induct)

107 apply force

108 apply (simp del: append_assoc add: append_assoc [symmetric])

109 apply (metis append_eq_appendI)

110 done

112 lemma append_one_prefix:

113 "prefix xs ys \<Longrightarrow> length xs < length ys \<Longrightarrow> prefix (xs @ [ys ! length xs]) ys"

114 proof (unfold prefix_def)

115 assume a1: "\<exists>zs. ys = xs @ zs"

116 then obtain sk :: "'a list" where sk: "ys = xs @ sk" by fastforce

117 assume a2: "length xs < length ys"

118 have f1: "\<And>v. ([]::'a list) @ v = v" using append_Nil2 by simp

119 have "[] \<noteq> sk" using a1 a2 sk less_not_refl by force

120 hence "\<exists>v. xs @ hd sk # v = ys" using sk by (metis hd_Cons_tl)

121 thus "\<exists>zs. ys = (xs @ [ys ! length xs]) @ zs" using f1 by fastforce

122 qed

124 theorem prefix_length_le: "prefix xs ys \<Longrightarrow> length xs \<le> length ys"

125 by (auto simp add: prefix_def)

127 lemma prefix_same_cases:

128 "prefix (xs\<^sub>1::'a list) ys \<Longrightarrow> prefix xs\<^sub>2 ys \<Longrightarrow> prefix xs\<^sub>1 xs\<^sub>2 \<or> prefix xs\<^sub>2 xs\<^sub>1"

129 unfolding prefix_def by (force simp: append_eq_append_conv2)

131 lemma prefix_length_prefix:

132 "prefix ps xs \<Longrightarrow> prefix qs xs \<Longrightarrow> length ps \<le> length qs \<Longrightarrow> prefix ps qs"

133 by (auto simp: prefix_def) (metis append_Nil2 append_eq_append_conv_if)

135 lemma set_mono_prefix: "prefix xs ys \<Longrightarrow> set xs \<subseteq> set ys"

136 by (auto simp add: prefix_def)

138 lemma take_is_prefix: "prefix (take n xs) xs"

139 unfolding prefix_def by (metis append_take_drop_id)

141 lemma prefixeq_butlast: "prefix (butlast xs) xs"

142 by (simp add: butlast_conv_take take_is_prefix)

144 lemma map_prefixI: "prefix xs ys \<Longrightarrow> prefix (map f xs) (map f ys)"

145 by (auto simp: prefix_def)

147 lemma prefix_length_less: "strict_prefix xs ys \<Longrightarrow> length xs < length ys"

148 by (auto simp: strict_prefix_def prefix_def)

150 lemma prefix_snocD: "prefix (xs@[x]) ys \<Longrightarrow> strict_prefix xs ys"

151 by (simp add: strict_prefixI' prefix_order.dual_order.strict_trans1)

153 lemma strict_prefix_simps [simp, code]:

154 "strict_prefix xs [] \<longleftrightarrow> False"

155 "strict_prefix [] (x # xs) \<longleftrightarrow> True"

156 "strict_prefix (x # xs) (y # ys) \<longleftrightarrow> x = y \<and> strict_prefix xs ys"

157 by (simp_all add: strict_prefix_def cong: conj_cong)

159 lemma take_strict_prefix: "strict_prefix xs ys \<Longrightarrow> strict_prefix (take n xs) ys"

160 proof (induct n arbitrary: xs ys)

161 case 0

162 then show ?case by (cases ys) simp_all

163 next

164 case (Suc n)

165 then show ?case by (metis prefix_order.less_trans strict_prefixI take_is_prefix)

166 qed

168 lemma not_prefix_cases:

169 assumes pfx: "\<not> prefix ps ls"

170 obtains

171 (c1) "ps \<noteq> []" and "ls = []"

172 | (c2) a as x xs where "ps = a#as" and "ls = x#xs" and "x = a" and "\<not> prefix as xs"

173 | (c3) a as x xs where "ps = a#as" and "ls = x#xs" and "x \<noteq> a"

174 proof (cases ps)

175 case Nil

176 then show ?thesis using pfx by simp

177 next

178 case (Cons a as)

179 note c = \<open>ps = a#as\<close>

180 show ?thesis

181 proof (cases ls)

182 case Nil then show ?thesis by (metis append_Nil2 pfx c1 same_prefix_nil)

183 next

184 case (Cons x xs)

185 show ?thesis

186 proof (cases "x = a")

187 case True

188 have "\<not> prefix as xs" using pfx c Cons True by simp

189 with c Cons True show ?thesis by (rule c2)

190 next

191 case False

192 with c Cons show ?thesis by (rule c3)

193 qed

194 qed

195 qed

197 lemma not_prefix_induct [consumes 1, case_names Nil Neq Eq]:

198 assumes np: "\<not> prefix ps ls"

199 and base: "\<And>x xs. P (x#xs) []"

200 and r1: "\<And>x xs y ys. x \<noteq> y \<Longrightarrow> P (x#xs) (y#ys)"

201 and r2: "\<And>x xs y ys. \<lbrakk> x = y; \<not> prefix xs ys; P xs ys \<rbrakk> \<Longrightarrow> P (x#xs) (y#ys)"

202 shows "P ps ls" using np

203 proof (induct ls arbitrary: ps)

204 case Nil

205 then show ?case

206 by (auto simp: neq_Nil_conv elim!: not_prefix_cases intro!: base)

207 next

208 case (Cons y ys)

209 then have npfx: "\<not> prefix ps (y # ys)" by simp

210 then obtain x xs where pv: "ps = x # xs"

211 by (rule not_prefix_cases) auto

212 show ?case by (metis Cons.hyps Cons_prefix_Cons npfx pv r1 r2)

213 qed

216 subsection \<open>Prefixes\<close>

218 primrec prefixes where

219 "prefixes [] = [[]]" |

220 "prefixes (x#xs) = [] # map (op # x) (prefixes xs)"

222 lemma in_set_prefixes[simp]: "xs \<in> set (prefixes ys) \<longleftrightarrow> prefix xs ys"

223 proof (induct xs arbitrary: ys)

224 case Nil

225 then show ?case by (cases ys) auto

226 next

227 case (Cons a xs)

228 then show ?case by (cases ys) auto

229 qed

231 lemma length_prefixes[simp]: "length (prefixes xs) = length xs+1"

232 by (induction xs) auto

234 lemma distinct_prefixes [intro]: "distinct (prefixes xs)"

235 by (induction xs) (auto simp: distinct_map)

237 lemma prefixes_snoc [simp]: "prefixes (xs@[x]) = prefixes xs @ [xs@[x]]"

238 by (induction xs) auto

240 lemma prefixes_not_Nil [simp]: "prefixes xs \<noteq> []"

241 by (cases xs) auto

243 lemma hd_prefixes [simp]: "hd (prefixes xs) = []"

244 by (cases xs) simp_all

246 lemma last_prefixes [simp]: "last (prefixes xs) = xs"

247 by (induction xs) (simp_all add: last_map)

249 lemma prefixes_append:

250 "prefixes (xs @ ys) = prefixes xs @ map (\<lambda>ys'. xs @ ys') (tl (prefixes ys))"

251 proof (induction xs)

252 case Nil

253 thus ?case by (cases ys) auto

254 qed simp_all

256 lemma prefixes_eq_snoc:

257 "prefixes ys = xs @ [x] \<longleftrightarrow>

258 (ys = [] \<and> xs = [] \<or> (\<exists>z zs. ys = zs@[z] \<and> xs = prefixes zs)) \<and> x = ys"

259 by (cases ys rule: rev_cases) auto

261 lemma prefixes_tailrec [code]:

262 "prefixes xs = rev (snd (foldl (\<lambda>(acc1, acc2) x. (x#acc1, rev (x#acc1)#acc2)) ([],[[]]) xs))"

263 proof -

264 have "foldl (\<lambda>(acc1, acc2) x. (x#acc1, rev (x#acc1)#acc2)) (ys, rev ys # zs) xs =

265 (rev xs @ ys, rev (map (\<lambda>as. rev ys @ as) (prefixes xs)) @ zs)" for ys zs

266 proof (induction xs arbitrary: ys zs)

267 case (Cons x xs ys zs)

268 from Cons.IH[of "x # ys" "rev ys # zs"]

269 show ?case by (simp add: o_def)

270 qed simp_all

271 from this [of "[]" "[]"] show ?thesis by simp

272 qed

274 lemma set_prefixes_eq: "set (prefixes xs) = {ys. prefix ys xs}"

275 by auto

277 lemma card_set_prefixes [simp]: "card (set (prefixes xs)) = Suc (length xs)"

278 by (subst distinct_card) auto

280 lemma set_prefixes_append:

281 "set (prefixes (xs @ ys)) = set (prefixes xs) \<union> {xs @ ys' |ys'. ys' \<in> set (prefixes ys)}"

282 by (subst prefixes_append, cases ys) auto

285 subsection \<open>Longest Common Prefix\<close>

287 definition Longest_common_prefix :: "'a list set \<Rightarrow> 'a list" where

288 "Longest_common_prefix L = (ARG_MAX length ps. \<forall>xs \<in> L. prefix ps xs)"

290 lemma Longest_common_prefix_ex: "L \<noteq> {} \<Longrightarrow>

291 \<exists>ps. (\<forall>xs \<in> L. prefix ps xs) \<and> (\<forall>qs. (\<forall>xs \<in> L. prefix qs xs) \<longrightarrow> size qs \<le> size ps)"

292 (is "_ \<Longrightarrow> \<exists>ps. ?P L ps")

293 proof(induction "LEAST n. \<exists>xs \<in>L. n = length xs" arbitrary: L)

294 case 0

295 have "[] : L" using "0.hyps" LeastI[of "\<lambda>n. \<exists>xs\<in>L. n = length xs"] \<open>L \<noteq> {}\<close>

296 by auto

297 hence "?P L []" by(auto)

298 thus ?case ..

299 next

300 case (Suc n)

301 let ?EX = "\<lambda>n. \<exists>xs\<in>L. n = length xs"

302 obtain x xs where xxs: "x#xs \<in> L" "size xs = n" using Suc.prems Suc.hyps(2)

303 by(metis LeastI_ex[of ?EX] Suc_length_conv ex_in_conv)

304 hence "[] \<notin> L" using Suc.hyps(2) by auto

305 show ?case

306 proof (cases "\<forall>xs \<in> L. \<exists>ys. xs = x#ys")

307 case True

308 let ?L = "{ys. x#ys \<in> L}"

309 have 1: "(LEAST n. \<exists>xs \<in> ?L. n = length xs) = n"

310 using xxs Suc.prems Suc.hyps(2) Least_le[of "?EX"]

311 by - (rule Least_equality, fastforce+)

312 have 2: "?L \<noteq> {}" using \<open>x # xs \<in> L\<close> by auto

313 from Suc.hyps(1)[OF 1[symmetric] 2] obtain ps where IH: "?P ?L ps" ..

314 { fix qs

315 assume "\<forall>qs. (\<forall>xa. x # xa \<in> L \<longrightarrow> prefix qs xa) \<longrightarrow> length qs \<le> length ps"

316 and "\<forall>xs\<in>L. prefix qs xs"

317 hence "length (tl qs) \<le> length ps"

318 by (metis Cons_prefix_Cons hd_Cons_tl list.sel(2) Nil_prefix)

319 hence "length qs \<le> Suc (length ps)" by auto

320 }

321 hence "?P L (x#ps)" using True IH by auto

322 thus ?thesis ..

323 next

324 case False

325 then obtain y ys where yys: "x\<noteq>y" "y#ys \<in> L" using \<open>[] \<notin> L\<close>

326 by (auto) (metis list.exhaust)

327 have "\<forall>qs. (\<forall>xs\<in>L. prefix qs xs) \<longrightarrow> qs = []" using yys \<open>x#xs \<in> L\<close>

328 by auto (metis Cons_prefix_Cons prefix_Cons)

329 hence "?P L []" by auto

330 thus ?thesis ..

331 qed

332 qed

334 lemma Longest_common_prefix_unique: "L \<noteq> {} \<Longrightarrow>

335 \<exists>! ps. (\<forall>xs \<in> L. prefix ps xs) \<and> (\<forall>qs. (\<forall>xs \<in> L. prefix qs xs) \<longrightarrow> size qs \<le> size ps)"

336 by(rule ex_ex1I[OF Longest_common_prefix_ex];

337 meson equals0I prefix_length_prefix prefix_order.antisym)

339 lemma Longest_common_prefix_eq:

340 "\<lbrakk> L \<noteq> {}; \<forall>xs \<in> L. prefix ps xs;

341 \<forall>qs. (\<forall>xs \<in> L. prefix qs xs) \<longrightarrow> size qs \<le> size ps \<rbrakk>

342 \<Longrightarrow> Longest_common_prefix L = ps"

343 unfolding Longest_common_prefix_def arg_max_def is_arg_max_linorder

344 by(rule some1_equality[OF Longest_common_prefix_unique]) auto

346 lemma Longest_common_prefix_prefix:

347 "xs \<in> L \<Longrightarrow> prefix (Longest_common_prefix L) xs"

348 unfolding Longest_common_prefix_def arg_max_def is_arg_max_linorder

349 by(rule someI2_ex[OF Longest_common_prefix_ex]) auto

351 lemma Longest_common_prefix_longest:

352 "L \<noteq> {} \<Longrightarrow> \<forall>xs\<in>L. prefix ps xs \<Longrightarrow> length ps \<le> length(Longest_common_prefix L)"

353 unfolding Longest_common_prefix_def arg_max_def is_arg_max_linorder

354 by(rule someI2_ex[OF Longest_common_prefix_ex]) auto

356 lemma Longest_common_prefix_max_prefix:

357 "L \<noteq> {} \<Longrightarrow> \<forall>xs\<in>L. prefix ps xs \<Longrightarrow> prefix ps (Longest_common_prefix L)"

358 by(metis Longest_common_prefix_prefix Longest_common_prefix_longest

359 prefix_length_prefix ex_in_conv)

361 lemma Longest_common_prefix_Nil: "[] \<in> L \<Longrightarrow> Longest_common_prefix L = []"

362 using Longest_common_prefix_prefix prefix_Nil by blast

364 lemma Longest_common_prefix_image_Cons: "L \<noteq> {} \<Longrightarrow>

365 Longest_common_prefix (op # x ` L) = x # Longest_common_prefix L"

366 apply(rule Longest_common_prefix_eq)

367 apply(simp)

368 apply (simp add: Longest_common_prefix_prefix)

369 apply simp

370 by(metis Longest_common_prefix_longest[of L] Cons_prefix_Cons Nitpick.size_list_simp(2)

371 Suc_le_mono hd_Cons_tl order.strict_implies_order zero_less_Suc)

373 lemma Longest_common_prefix_eq_Cons: assumes "L \<noteq> {}" "[] \<notin> L" "\<forall>xs\<in>L. hd xs = x"

374 shows "Longest_common_prefix L = x # Longest_common_prefix {ys. x#ys \<in> L}"

375 proof -

376 have "L = op # x ` {ys. x#ys \<in> L}" using assms(2,3)

377 by (auto simp: image_def)(metis hd_Cons_tl)

378 thus ?thesis

379 by (metis Longest_common_prefix_image_Cons image_is_empty assms(1))

380 qed

382 lemma Longest_common_prefix_eq_Nil:

383 "\<lbrakk>x#ys \<in> L; y#zs \<in> L; x \<noteq> y \<rbrakk> \<Longrightarrow> Longest_common_prefix L = []"

384 by (metis Longest_common_prefix_prefix list.inject prefix_Cons)

387 fun longest_common_prefix :: "'a list \<Rightarrow> 'a list \<Rightarrow> 'a list" where

388 "longest_common_prefix (x#xs) (y#ys) =

389 (if x=y then x # longest_common_prefix xs ys else [])" |

390 "longest_common_prefix _ _ = []"

392 lemma longest_common_prefix_prefix1:

393 "prefix (longest_common_prefix xs ys) xs"

394 by(induction xs ys rule: longest_common_prefix.induct) auto

396 lemma longest_common_prefix_prefix2:

397 "prefix (longest_common_prefix xs ys) ys"

398 by(induction xs ys rule: longest_common_prefix.induct) auto

400 lemma longest_common_prefix_max_prefix:

401 "\<lbrakk> prefix ps xs; prefix ps ys \<rbrakk>

402 \<Longrightarrow> prefix ps (longest_common_prefix xs ys)"

403 by(induction xs ys arbitrary: ps rule: longest_common_prefix.induct)

404 (auto simp: prefix_Cons)

407 subsection \<open>Parallel lists\<close>

409 definition parallel :: "'a list \<Rightarrow> 'a list \<Rightarrow> bool" (infixl "\<parallel>" 50)

410 where "(xs \<parallel> ys) = (\<not> prefix xs ys \<and> \<not> prefix ys xs)"

412 lemma parallelI [intro]: "\<not> prefix xs ys \<Longrightarrow> \<not> prefix ys xs \<Longrightarrow> xs \<parallel> ys"

413 unfolding parallel_def by blast

415 lemma parallelE [elim]:

416 assumes "xs \<parallel> ys"

417 obtains "\<not> prefix xs ys \<and> \<not> prefix ys xs"

418 using assms unfolding parallel_def by blast

420 theorem prefix_cases:

421 obtains "prefix xs ys" | "strict_prefix ys xs" | "xs \<parallel> ys"

422 unfolding parallel_def strict_prefix_def by blast

424 theorem parallel_decomp:

425 "xs \<parallel> ys \<Longrightarrow> \<exists>as b bs c cs. b \<noteq> c \<and> xs = as @ b # bs \<and> ys = as @ c # cs"

426 proof (induct xs rule: rev_induct)

427 case Nil

428 then have False by auto

429 then show ?case ..

430 next

431 case (snoc x xs)

432 show ?case

433 proof (rule prefix_cases)

434 assume le: "prefix xs ys"

435 then obtain ys' where ys: "ys = xs @ ys'" ..

436 show ?thesis

437 proof (cases ys')

438 assume "ys' = []"

439 then show ?thesis by (metis append_Nil2 parallelE prefixI snoc.prems ys)

440 next

441 fix c cs assume ys': "ys' = c # cs"

442 have "x \<noteq> c" using snoc.prems ys ys' by fastforce

443 thus "\<exists>as b bs c cs. b \<noteq> c \<and> xs @ [x] = as @ b # bs \<and> ys = as @ c # cs"

444 using ys ys' by blast

445 qed

446 next

447 assume "strict_prefix ys xs"

448 then have "prefix ys (xs @ [x])" by (simp add: strict_prefix_def)

449 with snoc have False by blast

450 then show ?thesis ..

451 next

452 assume "xs \<parallel> ys"

453 with snoc obtain as b bs c cs where neq: "(b::'a) \<noteq> c"

454 and xs: "xs = as @ b # bs" and ys: "ys = as @ c # cs"

455 by blast

456 from xs have "xs @ [x] = as @ b # (bs @ [x])" by simp

457 with neq ys show ?thesis by blast

458 qed

459 qed

461 lemma parallel_append: "a \<parallel> b \<Longrightarrow> a @ c \<parallel> b @ d"

462 apply (rule parallelI)

463 apply (erule parallelE, erule conjE,

464 induct rule: not_prefix_induct, simp+)+

465 done

467 lemma parallel_appendI: "xs \<parallel> ys \<Longrightarrow> x = xs @ xs' \<Longrightarrow> y = ys @ ys' \<Longrightarrow> x \<parallel> y"

468 by (simp add: parallel_append)

470 lemma parallel_commute: "a \<parallel> b \<longleftrightarrow> b \<parallel> a"

471 unfolding parallel_def by auto

474 subsection \<open>Suffix order on lists\<close>

476 definition suffix :: "'a list \<Rightarrow> 'a list \<Rightarrow> bool"

477 where "suffix xs ys = (\<exists>zs. ys = zs @ xs)"

479 definition strict_suffix :: "'a list \<Rightarrow> 'a list \<Rightarrow> bool"

480 where "strict_suffix xs ys \<longleftrightarrow> suffix xs ys \<and> xs \<noteq> ys"

482 interpretation suffix_order: order suffix strict_suffix

483 by standard (auto simp: suffix_def strict_suffix_def)

485 interpretation suffix_bot: order_bot Nil suffix strict_suffix

486 by standard (simp add: suffix_def)

488 lemma suffixI [intro?]: "ys = zs @ xs \<Longrightarrow> suffix xs ys"

489 unfolding suffix_def by blast

491 lemma suffixE [elim?]:

492 assumes "suffix xs ys"

493 obtains zs where "ys = zs @ xs"

494 using assms unfolding suffix_def by blast

496 lemma suffix_tl [simp]: "suffix (tl xs) xs"

497 by (induct xs) (auto simp: suffix_def)

499 lemma strict_suffix_tl [simp]: "xs \<noteq> [] \<Longrightarrow> strict_suffix (tl xs) xs"

500 by (induct xs) (auto simp: strict_suffix_def suffix_def)

502 lemma Nil_suffix [simp]: "suffix [] xs"

503 by (simp add: suffix_def)

505 lemma suffix_Nil [simp]: "(suffix xs []) = (xs = [])"

506 by (auto simp add: suffix_def)

508 lemma suffix_ConsI: "suffix xs ys \<Longrightarrow> suffix xs (y # ys)"

509 by (auto simp add: suffix_def)

511 lemma suffix_ConsD: "suffix (x # xs) ys \<Longrightarrow> suffix xs ys"

512 by (auto simp add: suffix_def)

514 lemma suffix_appendI: "suffix xs ys \<Longrightarrow> suffix xs (zs @ ys)"

515 by (auto simp add: suffix_def)

517 lemma suffix_appendD: "suffix (zs @ xs) ys \<Longrightarrow> suffix xs ys"

518 by (auto simp add: suffix_def)

520 lemma strict_suffix_set_subset: "strict_suffix xs ys \<Longrightarrow> set xs \<subseteq> set ys"

521 by (auto simp: strict_suffix_def suffix_def)

523 lemma suffix_set_subset: "suffix xs ys \<Longrightarrow> set xs \<subseteq> set ys"

524 by (auto simp: suffix_def)

526 lemma suffix_ConsD2: "suffix (x # xs) (y # ys) \<Longrightarrow> suffix xs ys"

527 proof -

528 assume "suffix (x # xs) (y # ys)"

529 then obtain zs where "y # ys = zs @ x # xs" ..

530 then show ?thesis

531 by (induct zs) (auto intro!: suffix_appendI suffix_ConsI)

532 qed

534 lemma suffix_to_prefix [code]: "suffix xs ys \<longleftrightarrow> prefix (rev xs) (rev ys)"

535 proof

536 assume "suffix xs ys"

537 then obtain zs where "ys = zs @ xs" ..

538 then have "rev ys = rev xs @ rev zs" by simp

539 then show "prefix (rev xs) (rev ys)" ..

540 next

541 assume "prefix (rev xs) (rev ys)"

542 then obtain zs where "rev ys = rev xs @ zs" ..

543 then have "rev (rev ys) = rev zs @ rev (rev xs)" by simp

544 then have "ys = rev zs @ xs" by simp

545 then show "suffix xs ys" ..

546 qed

548 lemma strict_suffix_to_prefix [code]: "strict_suffix xs ys \<longleftrightarrow> strict_prefix (rev xs) (rev ys)"

549 by (auto simp: suffix_to_prefix strict_suffix_def strict_prefix_def)

551 lemma distinct_suffix: "distinct ys \<Longrightarrow> suffix xs ys \<Longrightarrow> distinct xs"

552 by (clarsimp elim!: suffixE)

554 lemma suffix_map: "suffix xs ys \<Longrightarrow> suffix (map f xs) (map f ys)"

555 by (auto elim!: suffixE intro: suffixI)

557 lemma suffix_drop: "suffix (drop n as) as"

558 unfolding suffix_def by (rule exI [where x = "take n as"]) simp

560 lemma suffix_take: "suffix xs ys \<Longrightarrow> ys = take (length ys - length xs) ys @ xs"

561 by (auto elim!: suffixE)

563 lemma strict_suffix_reflclp_conv: "strict_suffix\<^sup>=\<^sup>= = suffix"

564 by (intro ext) (auto simp: suffix_def strict_suffix_def)

566 lemma suffix_lists: "suffix xs ys \<Longrightarrow> ys \<in> lists A \<Longrightarrow> xs \<in> lists A"

567 unfolding suffix_def by auto

569 lemma suffix_snoc [simp]: "suffix xs (ys @ [y]) \<longleftrightarrow> xs = [] \<or> (\<exists>zs. xs = zs @ [y] \<and> suffix zs ys)"

570 by (cases xs rule: rev_cases) (auto simp: suffix_def)

572 lemma snoc_suffix_snoc [simp]: "suffix (xs @ [x]) (ys @ [y]) = (x = y \<and> suffix xs ys)"

573 by (auto simp add: suffix_def)

575 lemma same_suffix_suffix [simp]: "suffix (ys @ xs) (zs @ xs) = suffix ys zs"

576 by (simp add: suffix_to_prefix)

578 lemma same_suffix_nil [simp]: "suffix (ys @ xs) xs = (ys = [])"

579 by (simp add: suffix_to_prefix)

581 theorem suffix_Cons: "suffix xs (y # ys) \<longleftrightarrow> xs = y # ys \<or> suffix xs ys"

582 unfolding suffix_def by (auto simp: Cons_eq_append_conv)

584 theorem suffix_append:

585 "suffix xs (ys @ zs) \<longleftrightarrow> suffix xs zs \<or> (\<exists>xs'. xs = xs' @ zs \<and> suffix xs' ys)"

586 by (auto simp: suffix_def append_eq_append_conv2)

588 theorem suffix_length_le: "suffix xs ys \<Longrightarrow> length xs \<le> length ys"

589 by (auto simp add: suffix_def)

591 lemma suffix_same_cases:

592 "suffix (xs\<^sub>1::'a list) ys \<Longrightarrow> suffix xs\<^sub>2 ys \<Longrightarrow> suffix xs\<^sub>1 xs\<^sub>2 \<or> suffix xs\<^sub>2 xs\<^sub>1"

593 unfolding suffix_def by (force simp: append_eq_append_conv2)

595 lemma suffix_length_suffix:

596 "suffix ps xs \<Longrightarrow> suffix qs xs \<Longrightarrow> length ps \<le> length qs \<Longrightarrow> suffix ps qs"

597 by (auto simp: suffix_to_prefix intro: prefix_length_prefix)

599 lemma suffix_length_less: "strict_suffix xs ys \<Longrightarrow> length xs < length ys"

600 by (auto simp: strict_suffix_def suffix_def)

602 lemma suffix_ConsD': "suffix (x#xs) ys \<Longrightarrow> strict_suffix xs ys"

603 by (auto simp: strict_suffix_def suffix_def)

605 lemma drop_strict_suffix: "strict_suffix xs ys \<Longrightarrow> strict_suffix (drop n xs) ys"

606 proof (induct n arbitrary: xs ys)

607 case 0

608 then show ?case by (cases ys) simp_all

609 next

610 case (Suc n)

611 then show ?case

612 by (cases xs) (auto intro: Suc dest: suffix_ConsD' suffix_order.less_imp_le)

613 qed

615 lemma not_suffix_cases:

616 assumes pfx: "\<not> suffix ps ls"

617 obtains

618 (c1) "ps \<noteq> []" and "ls = []"

619 | (c2) a as x xs where "ps = as@[a]" and "ls = xs@[x]" and "x = a" and "\<not> suffix as xs"

620 | (c3) a as x xs where "ps = as@[a]" and "ls = xs@[x]" and "x \<noteq> a"

621 proof (cases ps rule: rev_cases)

622 case Nil

623 then show ?thesis using pfx by simp

624 next

625 case (snoc as a)

626 note c = \<open>ps = as@[a]\<close>

627 show ?thesis

628 proof (cases ls rule: rev_cases)

629 case Nil then show ?thesis by (metis append_Nil2 pfx c1 same_suffix_nil)

630 next

631 case (snoc xs x)

632 show ?thesis

633 proof (cases "x = a")

634 case True

635 have "\<not> suffix as xs" using pfx c snoc True by simp

636 with c snoc True show ?thesis by (rule c2)

637 next

638 case False

639 with c snoc show ?thesis by (rule c3)

640 qed

641 qed

642 qed

644 lemma not_suffix_induct [consumes 1, case_names Nil Neq Eq]:

645 assumes np: "\<not> suffix ps ls"

646 and base: "\<And>x xs. P (xs@[x]) []"

647 and r1: "\<And>x xs y ys. x \<noteq> y \<Longrightarrow> P (xs@[x]) (ys@[y])"

648 and r2: "\<And>x xs y ys. \<lbrakk> x = y; \<not> suffix xs ys; P xs ys \<rbrakk> \<Longrightarrow> P (xs@[x]) (ys@[y])"

649 shows "P ps ls" using np

650 proof (induct ls arbitrary: ps rule: rev_induct)

651 case Nil

652 then show ?case by (cases ps rule: rev_cases) (auto intro: base)

653 next

654 case (snoc y ys ps)

655 then have npfx: "\<not> suffix ps (ys @ [y])" by simp

656 then obtain x xs where pv: "ps = xs @ [x]"

657 by (rule not_suffix_cases) auto

658 show ?case by (metis snoc.hyps snoc_suffix_snoc npfx pv r1 r2)

659 qed

662 lemma parallelD1: "x \<parallel> y \<Longrightarrow> \<not> prefix x y"

663 by blast

665 lemma parallelD2: "x \<parallel> y \<Longrightarrow> \<not> prefix y x"

666 by blast

668 lemma parallel_Nil1 [simp]: "\<not> x \<parallel> []"

669 unfolding parallel_def by simp

671 lemma parallel_Nil2 [simp]: "\<not> [] \<parallel> x"

672 unfolding parallel_def by simp

674 lemma Cons_parallelI1: "a \<noteq> b \<Longrightarrow> a # as \<parallel> b # bs"

675 by auto

677 lemma Cons_parallelI2: "\<lbrakk> a = b; as \<parallel> bs \<rbrakk> \<Longrightarrow> a # as \<parallel> b # bs"

678 by (metis Cons_prefix_Cons parallelE parallelI)

680 lemma not_equal_is_parallel:

681 assumes neq: "xs \<noteq> ys"

682 and len: "length xs = length ys"

683 shows "xs \<parallel> ys"

684 using len neq

685 proof (induct rule: list_induct2)

686 case Nil

687 then show ?case by simp

688 next

689 case (Cons a as b bs)

690 have ih: "as \<noteq> bs \<Longrightarrow> as \<parallel> bs" by fact

691 show ?case

692 proof (cases "a = b")

693 case True

694 then have "as \<noteq> bs" using Cons by simp

695 then show ?thesis by (rule Cons_parallelI2 [OF True ih])

696 next

697 case False

698 then show ?thesis by (rule Cons_parallelI1)

699 qed

700 qed

702 subsection \<open>Suffixes\<close>

704 primrec suffixes where

705 "suffixes [] = [[]]"

706 | "suffixes (x#xs) = suffixes xs @ [x # xs]"

708 lemma in_set_suffixes [simp]: "xs \<in> set (suffixes ys) \<longleftrightarrow> suffix xs ys"

709 by (induction ys) (auto simp: suffix_def Cons_eq_append_conv)

711 lemma distinct_suffixes [intro]: "distinct (suffixes xs)"

712 by (induction xs) (auto simp: suffix_def)

714 lemma length_suffixes [simp]: "length (suffixes xs) = Suc (length xs)"

715 by (induction xs) auto

717 lemma suffixes_snoc [simp]: "suffixes (xs @ [x]) = [] # map (\<lambda>ys. ys @ [x]) (suffixes xs)"

718 by (induction xs) auto

720 lemma suffixes_not_Nil [simp]: "suffixes xs \<noteq> []"

721 by (cases xs) auto

723 lemma hd_suffixes [simp]: "hd (suffixes xs) = []"

724 by (induction xs) simp_all

726 lemma last_suffixes [simp]: "last (suffixes xs) = xs"

727 by (cases xs) simp_all

729 lemma suffixes_append:

730 "suffixes (xs @ ys) = suffixes ys @ map (\<lambda>xs'. xs' @ ys) (tl (suffixes xs))"

731 proof (induction ys rule: rev_induct)

732 case Nil

733 thus ?case by (cases xs rule: rev_cases) auto

734 next

735 case (snoc y ys)

736 show ?case

737 by (simp only: append.assoc [symmetric] suffixes_snoc snoc.IH) simp

738 qed

740 lemma suffixes_eq_snoc:

741 "suffixes ys = xs @ [x] \<longleftrightarrow>

742 (ys = [] \<and> xs = [] \<or> (\<exists>z zs. ys = z#zs \<and> xs = suffixes zs)) \<and> x = ys"

743 by (cases ys) auto

745 lemma suffixes_tailrec [code]:

746 "suffixes xs = rev (snd (foldl (\<lambda>(acc1, acc2) x. (x#acc1, (x#acc1)#acc2)) ([],[[]]) (rev xs)))"

747 proof -

748 have "foldl (\<lambda>(acc1, acc2) x. (x#acc1, (x#acc1)#acc2)) (ys, ys # zs) (rev xs) =

749 (xs @ ys, rev (map (\<lambda>as. as @ ys) (suffixes xs)) @ zs)" for ys zs

750 proof (induction xs arbitrary: ys zs)

751 case (Cons x xs ys zs)

752 from Cons.IH[of ys zs]

753 show ?case by (simp add: o_def case_prod_unfold)

754 qed simp_all

755 from this [of "[]" "[]"] show ?thesis by simp

756 qed

758 lemma set_suffixes_eq: "set (suffixes xs) = {ys. suffix ys xs}"

759 by auto

761 lemma card_set_suffixes [simp]: "card (set (suffixes xs)) = Suc (length xs)"

762 by (subst distinct_card) auto

764 lemma set_suffixes_append:

765 "set (suffixes (xs @ ys)) = set (suffixes ys) \<union> {xs' @ ys |xs'. xs' \<in> set (suffixes xs)}"

766 by (subst suffixes_append, cases xs rule: rev_cases) auto

769 lemma suffixes_conv_prefixes: "suffixes xs = map rev (prefixes (rev xs))"

770 by (induction xs) auto

772 lemma prefixes_conv_suffixes: "prefixes xs = map rev (suffixes (rev xs))"

773 by (induction xs) auto

775 lemma prefixes_rev: "prefixes (rev xs) = map rev (suffixes xs)"

776 by (induction xs) auto

778 lemma suffixes_rev: "suffixes (rev xs) = map rev (prefixes xs)"

779 by (induction xs) auto

782 subsection \<open>Homeomorphic embedding on lists\<close>

784 inductive list_emb :: "('a \<Rightarrow> 'a \<Rightarrow> bool) \<Rightarrow> 'a list \<Rightarrow> 'a list \<Rightarrow> bool"

785 for P :: "('a \<Rightarrow> 'a \<Rightarrow> bool)"

786 where

787 list_emb_Nil [intro, simp]: "list_emb P [] ys"

788 | list_emb_Cons [intro] : "list_emb P xs ys \<Longrightarrow> list_emb P xs (y#ys)"

789 | list_emb_Cons2 [intro]: "P x y \<Longrightarrow> list_emb P xs ys \<Longrightarrow> list_emb P (x#xs) (y#ys)"

791 lemma list_emb_mono:

792 assumes "\<And>x y. P x y \<longrightarrow> Q x y"

793 shows "list_emb P xs ys \<longrightarrow> list_emb Q xs ys"

794 proof

795 assume "list_emb P xs ys"

796 then show "list_emb Q xs ys" by (induct) (auto simp: assms)

797 qed

799 lemma list_emb_Nil2 [simp]:

800 assumes "list_emb P xs []" shows "xs = []"

801 using assms by (cases rule: list_emb.cases) auto

803 lemma list_emb_refl:

804 assumes "\<And>x. x \<in> set xs \<Longrightarrow> P x x"

805 shows "list_emb P xs xs"

806 using assms by (induct xs) auto

808 lemma list_emb_Cons_Nil [simp]: "list_emb P (x#xs) [] = False"

809 proof -

810 { assume "list_emb P (x#xs) []"

811 from list_emb_Nil2 [OF this] have False by simp

812 } moreover {

813 assume False

814 then have "list_emb P (x#xs) []" by simp

815 } ultimately show ?thesis by blast

816 qed

818 lemma list_emb_append2 [intro]: "list_emb P xs ys \<Longrightarrow> list_emb P xs (zs @ ys)"

819 by (induct zs) auto

821 lemma list_emb_prefix [intro]:

822 assumes "list_emb P xs ys" shows "list_emb P xs (ys @ zs)"

823 using assms

824 by (induct arbitrary: zs) auto

826 lemma list_emb_ConsD:

827 assumes "list_emb P (x#xs) ys"

828 shows "\<exists>us v vs. ys = us @ v # vs \<and> P x v \<and> list_emb P xs vs"

829 using assms

830 proof (induct x \<equiv> "x # xs" ys arbitrary: x xs)

831 case list_emb_Cons

832 then show ?case by (metis append_Cons)

833 next

834 case (list_emb_Cons2 x y xs ys)

835 then show ?case by blast

836 qed

838 lemma list_emb_appendD:

839 assumes "list_emb P (xs @ ys) zs"

840 shows "\<exists>us vs. zs = us @ vs \<and> list_emb P xs us \<and> list_emb P ys vs"

841 using assms

842 proof (induction xs arbitrary: ys zs)

843 case Nil then show ?case by auto

844 next

845 case (Cons x xs)

846 then obtain us v vs where

847 zs: "zs = us @ v # vs" and p: "P x v" and lh: "list_emb P (xs @ ys) vs"

848 by (auto dest: list_emb_ConsD)

849 obtain sk\<^sub>0 :: "'a list \<Rightarrow> 'a list \<Rightarrow> 'a list" and sk\<^sub>1 :: "'a list \<Rightarrow> 'a list \<Rightarrow> 'a list" where

850 sk: "\<forall>x\<^sub>0 x\<^sub>1. \<not> list_emb P (xs @ x\<^sub>0) x\<^sub>1 \<or> sk\<^sub>0 x\<^sub>0 x\<^sub>1 @ sk\<^sub>1 x\<^sub>0 x\<^sub>1 = x\<^sub>1 \<and> list_emb P xs (sk\<^sub>0 x\<^sub>0 x\<^sub>1) \<and> list_emb P x\<^sub>0 (sk\<^sub>1 x\<^sub>0 x\<^sub>1)"

851 using Cons(1) by (metis (no_types))

852 hence "\<forall>x\<^sub>2. list_emb P (x # xs) (x\<^sub>2 @ v # sk\<^sub>0 ys vs)" using p lh by auto

853 thus ?case using lh zs sk by (metis (no_types) append_Cons append_assoc)

854 qed

856 lemma list_emb_strict_suffix:

857 assumes "list_emb P xs ys" and "strict_suffix ys zs"

858 shows "list_emb P xs zs"

859 using assms(2) and list_emb_append2 [OF assms(1)] by (auto simp: strict_suffix_def suffix_def)

861 lemma list_emb_suffix:

862 assumes "list_emb P xs ys" and "suffix ys zs"

863 shows "list_emb P xs zs"

864 using assms and list_emb_strict_suffix

865 unfolding strict_suffix_reflclp_conv[symmetric] by auto

867 lemma list_emb_length: "list_emb P xs ys \<Longrightarrow> length xs \<le> length ys"

868 by (induct rule: list_emb.induct) auto

870 lemma list_emb_trans:

871 assumes "\<And>x y z. \<lbrakk>x \<in> set xs; y \<in> set ys; z \<in> set zs; P x y; P y z\<rbrakk> \<Longrightarrow> P x z"

872 shows "\<lbrakk>list_emb P xs ys; list_emb P ys zs\<rbrakk> \<Longrightarrow> list_emb P xs zs"

873 proof -

874 assume "list_emb P xs ys" and "list_emb P ys zs"

875 then show "list_emb P xs zs" using assms

876 proof (induction arbitrary: zs)

877 case list_emb_Nil show ?case by blast

878 next

879 case (list_emb_Cons xs ys y)

880 from list_emb_ConsD [OF \<open>list_emb P (y#ys) zs\<close>] obtain us v vs

881 where zs: "zs = us @ v # vs" and "P\<^sup>=\<^sup>= y v" and "list_emb P ys vs" by blast

882 then have "list_emb P ys (v#vs)" by blast

883 then have "list_emb P ys zs" unfolding zs by (rule list_emb_append2)

884 from list_emb_Cons.IH [OF this] and list_emb_Cons.prems show ?case by auto

885 next

886 case (list_emb_Cons2 x y xs ys)

887 from list_emb_ConsD [OF \<open>list_emb P (y#ys) zs\<close>] obtain us v vs

888 where zs: "zs = us @ v # vs" and "P y v" and "list_emb P ys vs" by blast

889 with list_emb_Cons2 have "list_emb P xs vs" by auto

890 moreover have "P x v"

891 proof -

892 from zs have "v \<in> set zs" by auto

893 moreover have "x \<in> set (x#xs)" and "y \<in> set (y#ys)" by simp_all

894 ultimately show ?thesis

895 using \<open>P x y\<close> and \<open>P y v\<close> and list_emb_Cons2

896 by blast

897 qed

898 ultimately have "list_emb P (x#xs) (v#vs)" by blast

899 then show ?case unfolding zs by (rule list_emb_append2)

900 qed

901 qed

903 lemma list_emb_set:

904 assumes "list_emb P xs ys" and "x \<in> set xs"

905 obtains y where "y \<in> set ys" and "P x y"

906 using assms by (induct) auto

908 lemma list_emb_Cons_iff1 [simp]:

909 assumes "P x y"

910 shows "list_emb P (x#xs) (y#ys) \<longleftrightarrow> list_emb P xs ys"

911 using assms by (subst list_emb.simps) (auto dest: list_emb_ConsD)

913 lemma list_emb_Cons_iff2 [simp]:

914 assumes "\<not>P x y"

915 shows "list_emb P (x#xs) (y#ys) \<longleftrightarrow> list_emb P (x#xs) ys"

916 using assms by (subst list_emb.simps) auto

918 lemma list_emb_code [code]:

919 "list_emb P [] ys \<longleftrightarrow> True"

920 "list_emb P (x#xs) [] \<longleftrightarrow> False"

921 "list_emb P (x#xs) (y#ys) \<longleftrightarrow> (if P x y then list_emb P xs ys else list_emb P (x#xs) ys)"

922 by simp_all

925 subsection \<open>Subsequences (special case of homeomorphic embedding)\<close>

927 abbreviation subseq :: "'a list \<Rightarrow> 'a list \<Rightarrow> bool"

928 where "subseq xs ys \<equiv> list_emb (op =) xs ys"

930 definition strict_subseq where "strict_subseq xs ys \<longleftrightarrow> xs \<noteq> ys \<and> subseq xs ys"

932 lemma subseq_Cons2: "subseq xs ys \<Longrightarrow> subseq (x#xs) (x#ys)" by auto

934 lemma subseq_same_length:

935 assumes "subseq xs ys" and "length xs = length ys" shows "xs = ys"

936 using assms by (induct) (auto dest: list_emb_length)

938 lemma not_subseq_length [simp]: "length ys < length xs \<Longrightarrow> \<not> subseq xs ys"

939 by (metis list_emb_length linorder_not_less)

941 lemma subseq_Cons': "subseq (x#xs) ys \<Longrightarrow> subseq xs ys"

942 by (induct xs, simp, blast dest: list_emb_ConsD)

944 lemma subseq_Cons2':

945 assumes "subseq (x#xs) (x#ys)" shows "subseq xs ys"

946 using assms by (cases) (rule subseq_Cons')

948 lemma subseq_Cons2_neq:

949 assumes "subseq (x#xs) (y#ys)"

950 shows "x \<noteq> y \<Longrightarrow> subseq (x#xs) ys"

951 using assms by (cases) auto

953 lemma subseq_Cons2_iff [simp]:

954 "subseq (x#xs) (y#ys) = (if x = y then subseq xs ys else subseq (x#xs) ys)"

955 by simp

957 lemma subseq_append': "subseq (zs @ xs) (zs @ ys) \<longleftrightarrow> subseq xs ys"

958 by (induct zs) simp_all

960 interpretation subseq_order: order subseq strict_subseq

961 proof

962 fix xs ys :: "'a list"

963 {

964 assume "subseq xs ys" and "subseq ys xs"

965 thus "xs = ys"

966 proof (induct)

967 case list_emb_Nil

968 from list_emb_Nil2 [OF this] show ?case by simp

969 next

970 case list_emb_Cons2

971 thus ?case by simp

972 next

973 case list_emb_Cons

974 hence False using subseq_Cons' by fastforce

975 thus ?case ..

976 qed

977 }

978 thus "strict_subseq xs ys \<longleftrightarrow> (subseq xs ys \<and> \<not>subseq ys xs)"

979 by (auto simp: strict_subseq_def)

980 qed (auto simp: list_emb_refl intro: list_emb_trans)

982 lemma in_set_subseqs [simp]: "xs \<in> set (subseqs ys) \<longleftrightarrow> subseq xs ys"

983 proof

984 assume "xs \<in> set (subseqs ys)"

985 thus "subseq xs ys"

986 by (induction ys arbitrary: xs) (auto simp: Let_def)

987 next

988 have [simp]: "[] \<in> set (subseqs ys)" for ys :: "'a list"

989 by (induction ys) (auto simp: Let_def)

990 assume "subseq xs ys"

991 thus "xs \<in> set (subseqs ys)"

992 by (induction xs ys rule: list_emb.induct) (auto simp: Let_def)

993 qed

995 lemma set_subseqs_eq: "set (subseqs ys) = {xs. subseq xs ys}"

996 by auto

998 lemma subseq_append_le_same_iff: "subseq (xs @ ys) ys \<longleftrightarrow> xs = []"

999 by (auto dest: list_emb_length)

1001 lemma subseq_singleton_left: "subseq [x] ys \<longleftrightarrow> x \<in> set ys"

1002 by (fastforce dest: list_emb_ConsD split_list_last)

1004 lemma list_emb_append_mono:

1005 "\<lbrakk> list_emb P xs xs'; list_emb P ys ys' \<rbrakk> \<Longrightarrow> list_emb P (xs@ys) (xs'@ys')"

1006 by (induct rule: list_emb.induct) auto

1008 lemma prefix_imp_subseq [intro]: "prefix xs ys \<Longrightarrow> subseq xs ys"

1009 by (auto simp: prefix_def)

1011 lemma suffix_imp_subseq [intro]: "suffix xs ys \<Longrightarrow> subseq xs ys"

1012 by (auto simp: suffix_def)

1015 subsection \<open>Appending elements\<close>

1017 lemma subseq_append [simp]:

1018 "subseq (xs @ zs) (ys @ zs) \<longleftrightarrow> subseq xs ys" (is "?l = ?r")

1019 proof

1020 { fix xs' ys' xs ys zs :: "'a list" assume "subseq xs' ys'"

1021 then have "xs' = xs @ zs & ys' = ys @ zs \<longrightarrow> subseq xs ys"

1022 proof (induct arbitrary: xs ys zs)

1023 case list_emb_Nil show ?case by simp

1024 next

1025 case (list_emb_Cons xs' ys' x)

1026 { assume "ys=[]" then have ?case using list_emb_Cons(1) by auto }

1027 moreover

1028 { fix us assume "ys = x#us"

1029 then have ?case using list_emb_Cons(2) by(simp add: list_emb.list_emb_Cons) }

1030 ultimately show ?case by (auto simp:Cons_eq_append_conv)

1031 next

1032 case (list_emb_Cons2 x y xs' ys')

1033 { assume "xs=[]" then have ?case using list_emb_Cons2(1) by auto }

1034 moreover

1035 { fix us vs assume "xs=x#us" "ys=x#vs" then have ?case using list_emb_Cons2 by auto}

1036 moreover

1037 { fix us assume "xs=x#us" "ys=[]" then have ?case using list_emb_Cons2(2) by bestsimp }

1038 ultimately show ?case using \<open>op = x y\<close> by (auto simp: Cons_eq_append_conv)

1039 qed }

1040 moreover assume ?l

1041 ultimately show ?r by blast

1042 next

1043 assume ?r then show ?l by (metis list_emb_append_mono subseq_order.order_refl)

1044 qed

1046 lemma subseq_append_iff:

1047 "subseq xs (ys @ zs) \<longleftrightarrow> (\<exists>xs1 xs2. xs = xs1 @ xs2 \<and> subseq xs1 ys \<and> subseq xs2 zs)"

1048 (is "?lhs = ?rhs")

1049 proof

1050 assume ?lhs thus ?rhs

1051 proof (induction xs "ys @ zs" arbitrary: ys zs rule: list_emb.induct)

1052 case (list_emb_Cons xs ws y ys zs)

1053 from list_emb_Cons(2)[of "tl ys" zs] and list_emb_Cons(2)[of "[]" "tl zs"] and list_emb_Cons(1,3)

1054 show ?case by (cases ys) auto

1055 next

1056 case (list_emb_Cons2 x y xs ws ys zs)

1057 from list_emb_Cons2(3)[of "tl ys" zs] and list_emb_Cons2(3)[of "[]" "tl zs"]

1058 and list_emb_Cons2(1,2,4)

1059 show ?case by (cases ys) (auto simp: Cons_eq_append_conv)

1060 qed auto

1061 qed (auto intro: list_emb_append_mono)

1063 lemma subseq_appendE [case_names append]:

1064 assumes "subseq xs (ys @ zs)"

1065 obtains xs1 xs2 where "xs = xs1 @ xs2" "subseq xs1 ys" "subseq xs2 zs"

1066 using assms by (subst (asm) subseq_append_iff) auto

1068 lemma subseq_drop_many: "subseq xs ys \<Longrightarrow> subseq xs (zs @ ys)"

1069 by (induct zs) auto

1071 lemma subseq_rev_drop_many: "subseq xs ys \<Longrightarrow> subseq xs (ys @ zs)"

1072 by (metis append_Nil2 list_emb_Nil list_emb_append_mono)

1075 subsection \<open>Relation to standard list operations\<close>

1077 lemma subseq_map:

1078 assumes "subseq xs ys" shows "subseq (map f xs) (map f ys)"

1079 using assms by (induct) auto

1081 lemma subseq_filter_left [simp]: "subseq (filter P xs) xs"

1082 by (induct xs) auto

1084 lemma subseq_filter [simp]:

1085 assumes "subseq xs ys" shows "subseq (filter P xs) (filter P ys)"

1086 using assms by induct auto

1088 lemma subseq_conv_nths:

1089 "subseq xs ys \<longleftrightarrow> (\<exists>N. xs = nths ys N)" (is "?L = ?R")

1090 proof

1091 assume ?L

1092 then show ?R

1093 proof (induct)

1094 case list_emb_Nil show ?case by (metis nths_empty)

1095 next

1096 case (list_emb_Cons xs ys x)

1097 then obtain N where "xs = nths ys N" by blast

1098 then have "xs = nths (x#ys) (Suc ` N)"

1099 by (clarsimp simp add: nths_Cons inj_image_mem_iff)

1100 then show ?case by blast

1101 next

1102 case (list_emb_Cons2 x y xs ys)

1103 then obtain N where "xs = nths ys N" by blast

1104 then have "x#xs = nths (x#ys) (insert 0 (Suc ` N))"

1105 by (clarsimp simp add: nths_Cons inj_image_mem_iff)

1106 moreover from list_emb_Cons2 have "x = y" by simp

1107 ultimately show ?case by blast

1108 qed

1109 next

1110 assume ?R

1111 then obtain N where "xs = nths ys N" ..

1112 moreover have "subseq (nths ys N) ys"

1113 proof (induct ys arbitrary: N)

1114 case Nil show ?case by simp

1115 next

1116 case Cons then show ?case by (auto simp: nths_Cons)

1117 qed

1118 ultimately show ?L by simp

1119 qed

1122 subsection \<open>Contiguous sublists\<close>

1124 definition sublist :: "'a list \<Rightarrow> 'a list \<Rightarrow> bool" where

1125 "sublist xs ys = (\<exists>ps ss. ys = ps @ xs @ ss)"

1127 definition strict_sublist :: "'a list \<Rightarrow> 'a list \<Rightarrow> bool" where

1128 "strict_sublist xs ys \<longleftrightarrow> sublist xs ys \<and> xs \<noteq> ys"

1130 interpretation sublist_order: order sublist strict_sublist

1131 proof

1132 fix xs ys zs :: "'a list"

1133 assume "sublist xs ys" "sublist ys zs"

1134 then obtain xs1 xs2 ys1 ys2 where "ys = xs1 @ xs @ xs2" "zs = ys1 @ ys @ ys2"

1135 by (auto simp: sublist_def)

1136 hence "zs = (ys1 @ xs1) @ xs @ (xs2 @ ys2)" by simp

1137 thus "sublist xs zs" unfolding sublist_def by blast

1138 next

1139 fix xs ys :: "'a list"

1140 {

1141 assume "sublist xs ys" "sublist ys xs"

1142 then obtain as bs cs ds

1143 where xs: "xs = as @ ys @ bs" and ys: "ys = cs @ xs @ ds"

1144 by (auto simp: sublist_def)

1145 have "xs = as @ cs @ xs @ ds @ bs" by (subst xs, subst ys) auto

1146 also have "length \<dots> = length as + length cs + length xs + length bs + length ds"

1147 by simp

1148 finally have "as = []" "bs = []" by simp_all

1149 with xs show "xs = ys" by simp

1150 }

1151 thus "strict_sublist xs ys \<longleftrightarrow> (sublist xs ys \<and> \<not>sublist ys xs)"

1152 by (auto simp: strict_sublist_def)

1153 qed (auto simp: strict_sublist_def sublist_def intro: exI[of _ "[]"])

1155 lemma sublist_Nil_left [simp, intro]: "sublist [] ys"

1156 by (auto simp: sublist_def)

1158 lemma sublist_Cons_Nil [simp]: "\<not>sublist (x#xs) []"

1159 by (auto simp: sublist_def)

1161 lemma sublist_Nil_right [simp]: "sublist xs [] \<longleftrightarrow> xs = []"

1162 by (cases xs) auto

1164 lemma sublist_appendI [simp, intro]: "sublist xs (ps @ xs @ ss)"

1165 by (auto simp: sublist_def)

1167 lemma sublist_append_leftI [simp, intro]: "sublist xs (ps @ xs)"

1168 by (auto simp: sublist_def intro: exI[of _ "[]"])

1170 lemma sublist_append_rightI [simp, intro]: "sublist xs (xs @ ss)"

1171 by (auto simp: sublist_def intro: exI[of _ "[]"])

1173 lemma sublist_altdef: "sublist xs ys \<longleftrightarrow> (\<exists>ys'. prefix ys' ys \<and> suffix xs ys')"

1174 proof safe

1175 assume "sublist xs ys"

1176 then obtain ps ss where "ys = ps @ xs @ ss" by (auto simp: sublist_def)

1177 thus "\<exists>ys'. prefix ys' ys \<and> suffix xs ys'"

1178 by (intro exI[of _ "ps @ xs"] conjI suffix_appendI) auto

1179 next

1180 fix ys'

1181 assume "prefix ys' ys" "suffix xs ys'"

1182 thus "sublist xs ys" by (auto simp: prefix_def suffix_def)

1183 qed

1185 lemma sublist_altdef': "sublist xs ys \<longleftrightarrow> (\<exists>ys'. suffix ys' ys \<and> prefix xs ys')"

1186 proof safe

1187 assume "sublist xs ys"

1188 then obtain ps ss where "ys = ps @ xs @ ss" by (auto simp: sublist_def)

1189 thus "\<exists>ys'. suffix ys' ys \<and> prefix xs ys'"

1190 by (intro exI[of _ "xs @ ss"] conjI suffixI) auto

1191 next

1192 fix ys'

1193 assume "suffix ys' ys" "prefix xs ys'"

1194 thus "sublist xs ys" by (auto simp: prefix_def suffix_def)

1195 qed

1197 lemma sublist_Cons_right: "sublist xs (y # ys) \<longleftrightarrow> prefix xs (y # ys) \<or> sublist xs ys"

1198 by (auto simp: sublist_def prefix_def Cons_eq_append_conv)

1200 lemma sublist_code [code]:

1201 "sublist [] ys \<longleftrightarrow> True"

1202 "sublist (x # xs) [] \<longleftrightarrow> False"

1203 "sublist (x # xs) (y # ys) \<longleftrightarrow> prefix (x # xs) (y # ys) \<or> sublist (x # xs) ys"

1204 by (simp_all add: sublist_Cons_right)

1207 lemma sublist_append:

1208 "sublist xs (ys @ zs) \<longleftrightarrow>

1209 sublist xs ys \<or> sublist xs zs \<or> (\<exists>xs1 xs2. xs = xs1 @ xs2 \<and> suffix xs1 ys \<and> prefix xs2 zs)"

1210 by (auto simp: sublist_altdef prefix_append suffix_append)

1212 primrec sublists :: "'a list \<Rightarrow> 'a list list" where

1213 "sublists [] = [[]]"

1214 | "sublists (x # xs) = sublists xs @ map (op # x) (prefixes xs)"

1216 lemma in_set_sublists [simp]: "xs \<in> set (sublists ys) \<longleftrightarrow> sublist xs ys"

1217 by (induction ys arbitrary: xs) (auto simp: sublist_Cons_right prefix_Cons)

1219 lemma set_sublists_eq: "set (sublists xs) = {ys. sublist ys xs}"

1220 by auto

1222 lemma length_sublists [simp]: "length (sublists xs) = Suc (length xs * Suc (length xs) div 2)"

1223 by (induction xs) simp_all

1225 lemma sublist_length_le: "sublist xs ys \<Longrightarrow> length xs \<le> length ys"

1226 by (auto simp add: sublist_def)

1228 lemma set_mono_sublist: "sublist xs ys \<Longrightarrow> set xs \<subseteq> set ys"

1229 by (auto simp add: sublist_def)

1231 lemma prefix_imp_sublist [simp, intro]: "prefix xs ys \<Longrightarrow> sublist xs ys"

1232 by (auto simp: sublist_def prefix_def intro: exI[of _ "[]"])

1234 lemma suffix_imp_sublist [simp, intro]: "suffix xs ys \<Longrightarrow> sublist xs ys"

1235 by (auto simp: sublist_def suffix_def intro: exI[of _ "[]"])

1237 lemma sublist_take [simp, intro]: "sublist (take n xs) xs"

1238 by (rule prefix_imp_sublist) (simp_all add: take_is_prefix)

1240 lemma sublist_drop [simp, intro]: "sublist (drop n xs) xs"

1241 by (rule suffix_imp_sublist) (simp_all add: suffix_drop)

1243 lemma sublist_tl [simp, intro]: "sublist (tl xs) xs"

1244 by (rule suffix_imp_sublist) (simp_all add: suffix_drop)

1246 lemma sublist_butlast [simp, intro]: "sublist (butlast xs) xs"

1247 by (rule prefix_imp_sublist) (simp_all add: prefixeq_butlast)

1249 lemma sublist_rev [simp]: "sublist (rev xs) (rev ys) = sublist xs ys"

1250 proof

1251 assume "sublist (rev xs) (rev ys)"

1252 then obtain as bs where "rev ys = as @ rev xs @ bs"

1253 by (auto simp: sublist_def)

1254 also have "rev \<dots> = rev bs @ xs @ rev as" by simp

1255 finally show "sublist xs ys" by simp

1256 next

1257 assume "sublist xs ys"

1258 then obtain as bs where "ys = as @ xs @ bs"

1259 by (auto simp: sublist_def)

1260 also have "rev \<dots> = rev bs @ rev xs @ rev as" by simp

1261 finally show "sublist (rev xs) (rev ys)" by simp

1262 qed

1264 lemma sublist_rev_left: "sublist (rev xs) ys = sublist xs (rev ys)"

1265 by (subst sublist_rev [symmetric]) (simp only: rev_rev_ident)

1267 lemma sublist_rev_right: "sublist xs (rev ys) = sublist (rev xs) ys"

1268 by (subst sublist_rev [symmetric]) (simp only: rev_rev_ident)

1270 lemma snoc_sublist_snoc:

1271 "sublist (xs @ [x]) (ys @ [y]) \<longleftrightarrow>

1272 (x = y \<and> suffix xs ys \<or> sublist (xs @ [x]) ys) "

1273 by (subst (1 2) sublist_rev [symmetric])

1274 (simp del: sublist_rev add: sublist_Cons_right suffix_to_prefix)

1276 lemma sublist_snoc:

1277 "sublist xs (ys @ [y]) \<longleftrightarrow> suffix xs (ys @ [y]) \<or> sublist xs ys"

1278 by (subst (1 2) sublist_rev [symmetric])

1279 (simp del: sublist_rev add: sublist_Cons_right suffix_to_prefix)

1281 lemma sublist_imp_subseq [intro]: "sublist xs ys \<Longrightarrow> subseq xs ys"

1282 by (auto simp: sublist_def)

1284 subsection \<open>Parametricity\<close>

1286 context includes lifting_syntax

1287 begin

1289 private lemma prefix_primrec:

1290 "prefix = rec_list (\<lambda>xs. True) (\<lambda>x xs xsa ys.

1291 case ys of [] \<Rightarrow> False | y # ys \<Rightarrow> x = y \<and> xsa ys)"

1292 proof (intro ext, goal_cases)

1293 case (1 xs ys)

1294 show ?case by (induction xs arbitrary: ys) (auto simp: prefix_Cons split: list.splits)

1295 qed

1297 private lemma sublist_primrec:

1298 "sublist = (\<lambda>xs ys. rec_list (\<lambda>xs. xs = []) (\<lambda>y ys ysa xs. prefix xs (y # ys) \<or> ysa xs) ys xs)"

1299 proof (intro ext, goal_cases)

1300 case (1 xs ys)

1301 show ?case by (induction ys) (auto simp: sublist_Cons_right)

1302 qed

1304 private lemma list_emb_primrec:

1305 "list_emb = (\<lambda>uu uua uuaa. rec_list (\<lambda>P xs. List.null xs) (\<lambda>y ys ysa P xs. case xs of [] \<Rightarrow> True

1306 | x # xs \<Rightarrow> if P x y then ysa P xs else ysa P (x # xs)) uuaa uu uua)"

1307 proof (intro ext, goal_cases)

1308 case (1 P xs ys)

1309 show ?case

1310 by (induction ys arbitrary: xs)

1311 (auto simp: list_emb_code List.null_def split: list.splits)

1312 qed

1314 lemma prefix_transfer [transfer_rule]:

1315 assumes [transfer_rule]: "bi_unique A"

1316 shows "(list_all2 A ===> list_all2 A ===> op =) prefix prefix"

1317 unfolding prefix_primrec by transfer_prover

1319 lemma suffix_transfer [transfer_rule]:

1320 assumes [transfer_rule]: "bi_unique A"

1321 shows "(list_all2 A ===> list_all2 A ===> op =) suffix suffix"

1322 unfolding suffix_to_prefix [abs_def] by transfer_prover

1324 lemma sublist_transfer [transfer_rule]:

1325 assumes [transfer_rule]: "bi_unique A"

1326 shows "(list_all2 A ===> list_all2 A ===> op =) sublist sublist"

1327 unfolding sublist_primrec by transfer_prover

1329 lemma parallel_transfer [transfer_rule]:

1330 assumes [transfer_rule]: "bi_unique A"

1331 shows "(list_all2 A ===> list_all2 A ===> op =) parallel parallel"

1332 unfolding parallel_def by transfer_prover

1336 lemma list_emb_transfer [transfer_rule]:

1337 "((A ===> A ===> op =) ===> list_all2 A ===> list_all2 A ===> op =) list_emb list_emb"

1338 unfolding list_emb_primrec by transfer_prover

1340 lemma strict_prefix_transfer [transfer_rule]:

1341 assumes [transfer_rule]: "bi_unique A"

1342 shows "(list_all2 A ===> list_all2 A ===> op =) strict_prefix strict_prefix"

1343 unfolding strict_prefix_def by transfer_prover

1345 lemma strict_suffix_transfer [transfer_rule]:

1346 assumes [transfer_rule]: "bi_unique A"

1347 shows "(list_all2 A ===> list_all2 A ===> op =) strict_suffix strict_suffix"

1348 unfolding strict_suffix_def by transfer_prover

1350 lemma strict_subseq_transfer [transfer_rule]:

1351 assumes [transfer_rule]: "bi_unique A"

1352 shows "(list_all2 A ===> list_all2 A ===> op =) strict_subseq strict_subseq"

1353 unfolding strict_subseq_def by transfer_prover

1355 lemma strict_sublist_transfer [transfer_rule]:

1356 assumes [transfer_rule]: "bi_unique A"

1357 shows "(list_all2 A ===> list_all2 A ===> op =) strict_sublist strict_sublist"

1358 unfolding strict_sublist_def by transfer_prover

1360 lemma prefixes_transfer [transfer_rule]:

1361 assumes [transfer_rule]: "bi_unique A"

1362 shows "(list_all2 A ===> list_all2 (list_all2 A)) prefixes prefixes"

1363 unfolding prefixes_def by transfer_prover

1365 lemma suffixes_transfer [transfer_rule]:

1366 assumes [transfer_rule]: "bi_unique A"

1367 shows "(list_all2 A ===> list_all2 (list_all2 A)) suffixes suffixes"

1368 unfolding suffixes_def by transfer_prover

1370 lemma sublists_transfer [transfer_rule]:

1371 assumes [transfer_rule]: "bi_unique A"

1372 shows "(list_all2 A ===> list_all2 (list_all2 A)) sublists sublists"

1373 unfolding sublists_def by transfer_prover

1375 end

1377 end