src/HOL/Library/Sublist.thy
author wenzelm
Mon Sep 03 23:03:54 2012 +0200 (2012-09-03)
changeset 49107 ec34e9df0514
parent 49087 7a17ba4bc997
child 50516 ed6b40d15d1c
permissions -rw-r--r--
misc tuning;
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(*  Title:      HOL/Library/Sublist.thy
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    Author:     Tobias Nipkow and Markus Wenzel, TU Muenchen
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    Author:     Christian Sternagel, JAIST
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*)
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header {* List prefixes, suffixes, and embedding*}
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theory Sublist
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imports Main
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begin
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subsection {* Prefix order on lists *}
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definition prefixeq :: "'a list => 'a list => bool"
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  where "prefixeq xs ys \<longleftrightarrow> (\<exists>zs. ys = xs @ zs)"
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definition prefix :: "'a list => 'a list => bool"
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  where "prefix xs ys \<longleftrightarrow> prefixeq xs ys \<and> xs \<noteq> ys"
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interpretation prefix_order: order prefixeq prefix
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  by default (auto simp: prefixeq_def prefix_def)
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interpretation prefix_bot: bot prefixeq prefix Nil
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  by default (simp add: prefixeq_def)
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lemma prefixeqI [intro?]: "ys = xs @ zs ==> prefixeq xs ys"
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  unfolding prefixeq_def by blast
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lemma prefixeqE [elim?]:
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  assumes "prefixeq xs ys"
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  obtains zs where "ys = xs @ zs"
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  using assms unfolding prefixeq_def by blast
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lemma prefixI' [intro?]: "ys = xs @ z # zs ==> prefix xs ys"
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  unfolding prefix_def prefixeq_def by blast
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lemma prefixE' [elim?]:
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  assumes "prefix xs ys"
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  obtains z zs where "ys = xs @ z # zs"
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proof -
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  from `prefix xs ys` obtain us where "ys = xs @ us" and "xs \<noteq> ys"
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    unfolding prefix_def prefixeq_def by blast
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  with that show ?thesis by (auto simp add: neq_Nil_conv)
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qed
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lemma prefixI [intro?]: "prefixeq xs ys ==> xs \<noteq> ys ==> prefix xs ys"
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  unfolding prefix_def by blast
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lemma prefixE [elim?]:
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  fixes xs ys :: "'a list"
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  assumes "prefix xs ys"
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  obtains "prefixeq xs ys" and "xs \<noteq> ys"
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  using assms unfolding prefix_def by blast
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subsection {* Basic properties of prefixes *}
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theorem Nil_prefixeq [iff]: "prefixeq [] xs"
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  by (simp add: prefixeq_def)
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theorem prefixeq_Nil [simp]: "(prefixeq xs []) = (xs = [])"
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  by (induct xs) (simp_all add: prefixeq_def)
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lemma prefixeq_snoc [simp]: "prefixeq xs (ys @ [y]) \<longleftrightarrow> xs = ys @ [y] \<or> prefixeq xs ys"
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proof
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  assume "prefixeq xs (ys @ [y])"
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  then obtain zs where zs: "ys @ [y] = xs @ zs" ..
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  show "xs = ys @ [y] \<or> prefixeq xs ys"
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    by (metis append_Nil2 butlast_append butlast_snoc prefixeqI zs)
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next
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  assume "xs = ys @ [y] \<or> prefixeq xs ys"
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  then show "prefixeq xs (ys @ [y])"
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    by (metis prefix_order.eq_iff prefix_order.order_trans prefixeqI)
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qed
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lemma Cons_prefixeq_Cons [simp]: "prefixeq (x # xs) (y # ys) = (x = y \<and> prefixeq xs ys)"
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  by (auto simp add: prefixeq_def)
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lemma prefixeq_code [code]:
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  "prefixeq [] xs \<longleftrightarrow> True"
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  "prefixeq (x # xs) [] \<longleftrightarrow> False"
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  "prefixeq (x # xs) (y # ys) \<longleftrightarrow> x = y \<and> prefixeq xs ys"
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  by simp_all
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lemma same_prefixeq_prefixeq [simp]: "prefixeq (xs @ ys) (xs @ zs) = prefixeq ys zs"
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  by (induct xs) simp_all
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lemma same_prefixeq_nil [iff]: "prefixeq (xs @ ys) xs = (ys = [])"
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  by (metis append_Nil2 append_self_conv prefix_order.eq_iff prefixeqI)
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lemma prefixeq_prefixeq [simp]: "prefixeq xs ys ==> prefixeq xs (ys @ zs)"
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  by (metis prefix_order.le_less_trans prefixeqI prefixE prefixI)
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lemma append_prefixeqD: "prefixeq (xs @ ys) zs \<Longrightarrow> prefixeq xs zs"
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  by (auto simp add: prefixeq_def)
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theorem prefixeq_Cons: "prefixeq xs (y # ys) = (xs = [] \<or> (\<exists>zs. xs = y # zs \<and> prefixeq zs ys))"
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  by (cases xs) (auto simp add: prefixeq_def)
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theorem prefixeq_append:
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  "prefixeq xs (ys @ zs) = (prefixeq xs ys \<or> (\<exists>us. xs = ys @ us \<and> prefixeq us zs))"
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  apply (induct zs rule: rev_induct)
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   apply force
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  apply (simp del: append_assoc add: append_assoc [symmetric])
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  apply (metis append_eq_appendI)
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  done
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lemma append_one_prefixeq:
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  "prefixeq xs ys ==> length xs < length ys ==> prefixeq (xs @ [ys ! length xs]) ys"
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  unfolding prefixeq_def
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  by (metis Cons_eq_appendI append_eq_appendI append_eq_conv_conj
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    eq_Nil_appendI nth_drop')
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theorem prefixeq_length_le: "prefixeq xs ys ==> length xs \<le> length ys"
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  by (auto simp add: prefixeq_def)
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lemma prefixeq_same_cases:
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  "prefixeq (xs\<^isub>1::'a list) ys \<Longrightarrow> prefixeq xs\<^isub>2 ys \<Longrightarrow> prefixeq xs\<^isub>1 xs\<^isub>2 \<or> prefixeq xs\<^isub>2 xs\<^isub>1"
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  unfolding prefixeq_def by (metis append_eq_append_conv2)
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lemma set_mono_prefixeq: "prefixeq xs ys \<Longrightarrow> set xs \<subseteq> set ys"
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  by (auto simp add: prefixeq_def)
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lemma take_is_prefixeq: "prefixeq (take n xs) xs"
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  unfolding prefixeq_def by (metis append_take_drop_id)
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lemma map_prefixeqI: "prefixeq xs ys \<Longrightarrow> prefixeq (map f xs) (map f ys)"
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  by (auto simp: prefixeq_def)
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lemma prefixeq_length_less: "prefix xs ys \<Longrightarrow> length xs < length ys"
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  by (auto simp: prefix_def prefixeq_def)
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lemma prefix_simps [simp, code]:
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  "prefix xs [] \<longleftrightarrow> False"
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  "prefix [] (x # xs) \<longleftrightarrow> True"
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  "prefix (x # xs) (y # ys) \<longleftrightarrow> x = y \<and> prefix xs ys"
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  by (simp_all add: prefix_def cong: conj_cong)
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lemma take_prefix: "prefix xs ys \<Longrightarrow> prefix (take n xs) ys"
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  apply (induct n arbitrary: xs ys)
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   apply (case_tac ys, simp_all)[1]
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  apply (metis prefix_order.less_trans prefixI take_is_prefixeq)
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  done
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lemma not_prefixeq_cases:
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  assumes pfx: "\<not> prefixeq ps ls"
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  obtains
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    (c1) "ps \<noteq> []" and "ls = []"
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  | (c2) a as x xs where "ps = a#as" and "ls = x#xs" and "x = a" and "\<not> prefixeq as xs"
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  | (c3) a as x xs where "ps = a#as" and "ls = x#xs" and "x \<noteq> a"
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proof (cases ps)
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  case Nil
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  then show ?thesis using pfx by simp
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next
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  case (Cons a as)
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  note c = `ps = a#as`
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  show ?thesis
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  proof (cases ls)
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    case Nil then show ?thesis by (metis append_Nil2 pfx c1 same_prefixeq_nil)
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  next
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    case (Cons x xs)
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    show ?thesis
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    proof (cases "x = a")
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      case True
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      have "\<not> prefixeq as xs" using pfx c Cons True by simp
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      with c Cons True show ?thesis by (rule c2)
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    next
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      case False
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      with c Cons show ?thesis by (rule c3)
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    qed
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  qed
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qed
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lemma not_prefixeq_induct [consumes 1, case_names Nil Neq Eq]:
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  assumes np: "\<not> prefixeq ps ls"
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    and base: "\<And>x xs. P (x#xs) []"
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    and r1: "\<And>x xs y ys. x \<noteq> y \<Longrightarrow> P (x#xs) (y#ys)"
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    and r2: "\<And>x xs y ys. \<lbrakk> x = y; \<not> prefixeq xs ys; P xs ys \<rbrakk> \<Longrightarrow> P (x#xs) (y#ys)"
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  shows "P ps ls" using np
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proof (induct ls arbitrary: ps)
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  case Nil then show ?case
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    by (auto simp: neq_Nil_conv elim!: not_prefixeq_cases intro!: base)
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next
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  case (Cons y ys)
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  then have npfx: "\<not> prefixeq ps (y # ys)" by simp
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  then obtain x xs where pv: "ps = x # xs"
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    by (rule not_prefixeq_cases) auto
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  show ?case by (metis Cons.hyps Cons_prefixeq_Cons npfx pv r1 r2)
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qed
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subsection {* Parallel lists *}
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definition parallel :: "'a list => 'a list => bool"  (infixl "\<parallel>" 50)
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  where "(xs \<parallel> ys) = (\<not> prefixeq xs ys \<and> \<not> prefixeq ys xs)"
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lemma parallelI [intro]: "\<not> prefixeq xs ys ==> \<not> prefixeq ys xs ==> xs \<parallel> ys"
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  unfolding parallel_def by blast
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lemma parallelE [elim]:
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  assumes "xs \<parallel> ys"
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  obtains "\<not> prefixeq xs ys \<and> \<not> prefixeq ys xs"
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  using assms unfolding parallel_def by blast
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theorem prefixeq_cases:
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  obtains "prefixeq xs ys" | "prefix ys xs" | "xs \<parallel> ys"
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  unfolding parallel_def prefix_def by blast
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theorem parallel_decomp:
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  "xs \<parallel> ys ==> \<exists>as b bs c cs. b \<noteq> c \<and> xs = as @ b # bs \<and> ys = as @ c # cs"
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proof (induct xs rule: rev_induct)
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  case Nil
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  then have False by auto
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  then show ?case ..
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next
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  case (snoc x xs)
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  show ?case
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  proof (rule prefixeq_cases)
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    assume le: "prefixeq xs ys"
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    then obtain ys' where ys: "ys = xs @ ys'" ..
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    show ?thesis
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    proof (cases ys')
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      assume "ys' = []"
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      then show ?thesis by (metis append_Nil2 parallelE prefixeqI snoc.prems ys)
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    next
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      fix c cs assume ys': "ys' = c # cs"
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      then show ?thesis
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        by (metis Cons_eq_appendI eq_Nil_appendI parallelE prefixeqI
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          same_prefixeq_prefixeq snoc.prems ys)
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    qed
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  next
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    assume "prefix ys xs"
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    then have "prefixeq ys (xs @ [x])" by (simp add: prefix_def)
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    with snoc have False by blast
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    then show ?thesis ..
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  next
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    assume "xs \<parallel> ys"
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    with snoc obtain as b bs c cs where neq: "(b::'a) \<noteq> c"
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      and xs: "xs = as @ b # bs" and ys: "ys = as @ c # cs"
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      by blast
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    from xs have "xs @ [x] = as @ b # (bs @ [x])" by simp
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    with neq ys show ?thesis by blast
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  qed
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qed
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lemma parallel_append: "a \<parallel> b \<Longrightarrow> a @ c \<parallel> b @ d"
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  apply (rule parallelI)
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    apply (erule parallelE, erule conjE,
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      induct rule: not_prefixeq_induct, simp+)+
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  done
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lemma parallel_appendI: "xs \<parallel> ys \<Longrightarrow> x = xs @ xs' \<Longrightarrow> y = ys @ ys' \<Longrightarrow> x \<parallel> y"
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  by (simp add: parallel_append)
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lemma parallel_commute: "a \<parallel> b \<longleftrightarrow> b \<parallel> a"
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  unfolding parallel_def by auto
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subsection {* Suffix order on lists *}
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definition suffixeq :: "'a list \<Rightarrow> 'a list \<Rightarrow> bool"
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  where "suffixeq xs ys = (\<exists>zs. ys = zs @ xs)"
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definition suffix :: "'a list \<Rightarrow> 'a list \<Rightarrow> bool"
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  where "suffix xs ys \<longleftrightarrow> (\<exists>us. ys = us @ xs \<and> us \<noteq> [])"
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lemma suffix_imp_suffixeq:
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  "suffix xs ys \<Longrightarrow> suffixeq xs ys"
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  by (auto simp: suffixeq_def suffix_def)
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lemma suffixeqI [intro?]: "ys = zs @ xs ==> suffixeq xs ys"
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  unfolding suffixeq_def by blast
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lemma suffixeqE [elim?]:
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  assumes "suffixeq xs ys"
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  obtains zs where "ys = zs @ xs"
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  using assms unfolding suffixeq_def by blast
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lemma suffixeq_refl [iff]: "suffixeq xs xs"
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  by (auto simp add: suffixeq_def)
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lemma suffix_trans:
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  "suffix xs ys \<Longrightarrow> suffix ys zs \<Longrightarrow> suffix xs zs"
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  by (auto simp: suffix_def)
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lemma suffixeq_trans: "\<lbrakk>suffixeq xs ys; suffixeq ys zs\<rbrakk> \<Longrightarrow> suffixeq xs zs"
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  by (auto simp add: suffixeq_def)
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lemma suffixeq_antisym: "\<lbrakk>suffixeq xs ys; suffixeq ys xs\<rbrakk> \<Longrightarrow> xs = ys"
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  by (auto simp add: suffixeq_def)
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lemma suffixeq_tl [simp]: "suffixeq (tl xs) xs"
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  by (induct xs) (auto simp: suffixeq_def)
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lemma suffix_tl [simp]: "xs \<noteq> [] \<Longrightarrow> suffix (tl xs) xs"
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  by (induct xs) (auto simp: suffix_def)
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lemma Nil_suffixeq [iff]: "suffixeq [] xs"
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  by (simp add: suffixeq_def)
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lemma suffixeq_Nil [simp]: "(suffixeq xs []) = (xs = [])"
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  by (auto simp add: suffixeq_def)
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lemma suffixeq_ConsI: "suffixeq xs ys \<Longrightarrow> suffixeq xs (y # ys)"
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  by (auto simp add: suffixeq_def)
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lemma suffixeq_ConsD: "suffixeq (x # xs) ys \<Longrightarrow> suffixeq xs ys"
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  by (auto simp add: suffixeq_def)
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lemma suffixeq_appendI: "suffixeq xs ys \<Longrightarrow> suffixeq xs (zs @ ys)"
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  by (auto simp add: suffixeq_def)
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lemma suffixeq_appendD: "suffixeq (zs @ xs) ys \<Longrightarrow> suffixeq xs ys"
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  by (auto simp add: suffixeq_def)
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lemma suffix_set_subset:
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  "suffix xs ys \<Longrightarrow> set xs \<subseteq> set ys" by (auto simp: suffix_def)
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lemma suffixeq_set_subset:
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  "suffixeq xs ys \<Longrightarrow> set xs \<subseteq> set ys" by (auto simp: suffixeq_def)
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lemma suffixeq_ConsD2: "suffixeq (x # xs) (y # ys) \<Longrightarrow> suffixeq xs ys"
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proof -
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  assume "suffixeq (x # xs) (y # ys)"
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  then obtain zs where "y # ys = zs @ x # xs" ..
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  then show ?thesis
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    by (induct zs) (auto intro!: suffixeq_appendI suffixeq_ConsI)
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qed
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lemma suffixeq_to_prefixeq [code]: "suffixeq xs ys \<longleftrightarrow> prefixeq (rev xs) (rev ys)"
Christian@49087
   325
proof
Christian@49087
   326
  assume "suffixeq xs ys"
Christian@49087
   327
  then obtain zs where "ys = zs @ xs" ..
Christian@49087
   328
  then have "rev ys = rev xs @ rev zs" by simp
Christian@49087
   329
  then show "prefixeq (rev xs) (rev ys)" ..
Christian@49087
   330
next
Christian@49087
   331
  assume "prefixeq (rev xs) (rev ys)"
Christian@49087
   332
  then obtain zs where "rev ys = rev xs @ zs" ..
Christian@49087
   333
  then have "rev (rev ys) = rev zs @ rev (rev xs)" by simp
Christian@49087
   334
  then have "ys = rev zs @ xs" by simp
Christian@49087
   335
  then show "suffixeq xs ys" ..
wenzelm@21305
   336
qed
oheimb@14538
   337
Christian@49087
   338
lemma distinct_suffixeq: "distinct ys \<Longrightarrow> suffixeq xs ys \<Longrightarrow> distinct xs"
Christian@49087
   339
  by (clarsimp elim!: suffixeqE)
wenzelm@17201
   340
Christian@49087
   341
lemma suffixeq_map: "suffixeq xs ys \<Longrightarrow> suffixeq (map f xs) (map f ys)"
Christian@49087
   342
  by (auto elim!: suffixeqE intro: suffixeqI)
kleing@25299
   343
Christian@49087
   344
lemma suffixeq_drop: "suffixeq (drop n as) as"
Christian@49087
   345
  unfolding suffixeq_def
wenzelm@25692
   346
  apply (rule exI [where x = "take n as"])
wenzelm@25692
   347
  apply simp
wenzelm@25692
   348
  done
kleing@25299
   349
Christian@49087
   350
lemma suffixeq_take: "suffixeq xs ys \<Longrightarrow> ys = take (length ys - length xs) ys @ xs"
wenzelm@49107
   351
  by (auto elim!: suffixeqE)
kleing@25299
   352
wenzelm@49107
   353
lemma suffixeq_suffix_reflclp_conv: "suffixeq = suffix\<^sup>=\<^sup>="
Christian@49087
   354
proof (intro ext iffI)
Christian@49087
   355
  fix xs ys :: "'a list"
Christian@49087
   356
  assume "suffixeq xs ys"
Christian@49087
   357
  show "suffix\<^sup>=\<^sup>= xs ys"
Christian@49087
   358
  proof
Christian@49087
   359
    assume "xs \<noteq> ys"
wenzelm@49107
   360
    with `suffixeq xs ys` show "suffix xs ys"
wenzelm@49107
   361
      by (auto simp: suffixeq_def suffix_def)
Christian@49087
   362
  qed
Christian@49087
   363
next
Christian@49087
   364
  fix xs ys :: "'a list"
Christian@49087
   365
  assume "suffix\<^sup>=\<^sup>= xs ys"
wenzelm@49107
   366
  then show "suffixeq xs ys"
Christian@49087
   367
  proof
wenzelm@49107
   368
    assume "suffix xs ys" then show "suffixeq xs ys"
wenzelm@49107
   369
      by (rule suffix_imp_suffixeq)
Christian@49087
   370
  next
wenzelm@49107
   371
    assume "xs = ys" then show "suffixeq xs ys"
wenzelm@49107
   372
      by (auto simp: suffixeq_def)
Christian@49087
   373
  qed
Christian@49087
   374
qed
Christian@49087
   375
Christian@49087
   376
lemma parallelD1: "x \<parallel> y \<Longrightarrow> \<not> prefixeq x y"
wenzelm@25692
   377
  by blast
kleing@25299
   378
Christian@49087
   379
lemma parallelD2: "x \<parallel> y \<Longrightarrow> \<not> prefixeq y x"
wenzelm@25692
   380
  by blast
wenzelm@25355
   381
wenzelm@25355
   382
lemma parallel_Nil1 [simp]: "\<not> x \<parallel> []"
wenzelm@25692
   383
  unfolding parallel_def by simp
wenzelm@25355
   384
kleing@25299
   385
lemma parallel_Nil2 [simp]: "\<not> [] \<parallel> x"
wenzelm@25692
   386
  unfolding parallel_def by simp
kleing@25299
   387
nipkow@25564
   388
lemma Cons_parallelI1: "a \<noteq> b \<Longrightarrow> a # as \<parallel> b # bs"
wenzelm@25692
   389
  by auto
kleing@25299
   390
nipkow@25564
   391
lemma Cons_parallelI2: "\<lbrakk> a = b; as \<parallel> bs \<rbrakk> \<Longrightarrow> a # as \<parallel> b # bs"
Christian@49087
   392
  by (metis Cons_prefixeq_Cons parallelE parallelI)
nipkow@25665
   393
kleing@25299
   394
lemma not_equal_is_parallel:
kleing@25299
   395
  assumes neq: "xs \<noteq> ys"
wenzelm@25356
   396
    and len: "length xs = length ys"
wenzelm@25356
   397
  shows "xs \<parallel> ys"
kleing@25299
   398
  using len neq
wenzelm@25355
   399
proof (induct rule: list_induct2)
haftmann@26445
   400
  case Nil
wenzelm@25356
   401
  then show ?case by simp
kleing@25299
   402
next
haftmann@26445
   403
  case (Cons a as b bs)
wenzelm@25355
   404
  have ih: "as \<noteq> bs \<Longrightarrow> as \<parallel> bs" by fact
kleing@25299
   405
  show ?case
kleing@25299
   406
  proof (cases "a = b")
wenzelm@25355
   407
    case True
haftmann@26445
   408
    then have "as \<noteq> bs" using Cons by simp
wenzelm@25355
   409
    then show ?thesis by (rule Cons_parallelI2 [OF True ih])
kleing@25299
   410
  next
kleing@25299
   411
    case False
wenzelm@25355
   412
    then show ?thesis by (rule Cons_parallelI1)
kleing@25299
   413
  qed
kleing@25299
   414
qed
haftmann@22178
   415
wenzelm@49107
   416
lemma suffix_reflclp_conv: "suffix\<^sup>=\<^sup>= = suffixeq"
Christian@49087
   417
  by (intro ext) (auto simp: suffixeq_def suffix_def)
Christian@49087
   418
wenzelm@49107
   419
lemma suffix_lists: "suffix xs ys \<Longrightarrow> ys \<in> lists A \<Longrightarrow> xs \<in> lists A"
Christian@49087
   420
  unfolding suffix_def by auto
Christian@49087
   421
Christian@49087
   422
Christian@49087
   423
subsection {* Embedding on lists *}
Christian@49087
   424
wenzelm@49107
   425
inductive emb :: "('a \<Rightarrow> 'a \<Rightarrow> bool) \<Rightarrow> 'a list \<Rightarrow> 'a list \<Rightarrow> bool"
Christian@49087
   426
  for P :: "('a \<Rightarrow> 'a \<Rightarrow> bool)"
Christian@49087
   427
where
Christian@49087
   428
  emb_Nil [intro, simp]: "emb P [] ys"
Christian@49087
   429
| emb_Cons [intro] : "emb P xs ys \<Longrightarrow> emb P xs (y#ys)"
Christian@49087
   430
| emb_Cons2 [intro]: "P x y \<Longrightarrow> emb P xs ys \<Longrightarrow> emb P (x#xs) (y#ys)"
Christian@49087
   431
Christian@49087
   432
lemma emb_Nil2 [simp]:
Christian@49087
   433
  assumes "emb P xs []" shows "xs = []"
Christian@49087
   434
  using assms by (cases rule: emb.cases) auto
Christian@49087
   435
wenzelm@49107
   436
lemma emb_Cons_Nil [simp]: "emb P (x#xs) [] = False"
Christian@49087
   437
proof -
Christian@49087
   438
  { assume "emb P (x#xs) []"
Christian@49087
   439
    from emb_Nil2 [OF this] have False by simp
Christian@49087
   440
  } moreover {
Christian@49087
   441
    assume False
wenzelm@49107
   442
    then have "emb P (x#xs) []" by simp
Christian@49087
   443
  } ultimately show ?thesis by blast
Christian@49087
   444
qed
Christian@49087
   445
wenzelm@49107
   446
lemma emb_append2 [intro]: "emb P xs ys \<Longrightarrow> emb P xs (zs @ ys)"
Christian@49087
   447
  by (induct zs) auto
Christian@49087
   448
Christian@49087
   449
lemma emb_prefix [intro]:
Christian@49087
   450
  assumes "emb P xs ys" shows "emb P xs (ys @ zs)"
Christian@49087
   451
  using assms
Christian@49087
   452
  by (induct arbitrary: zs) auto
Christian@49087
   453
Christian@49087
   454
lemma emb_ConsD:
Christian@49087
   455
  assumes "emb P (x#xs) ys"
Christian@49087
   456
  shows "\<exists>us v vs. ys = us @ v # vs \<and> P x v \<and> emb P xs vs"
Christian@49087
   457
using assms
wenzelm@49107
   458
proof (induct x \<equiv> "x # xs" ys arbitrary: x xs)
wenzelm@49107
   459
  case emb_Cons
wenzelm@49107
   460
  then show ?case by (metis append_Cons)
Christian@49087
   461
next
Christian@49087
   462
  case (emb_Cons2 x y xs ys)
wenzelm@49107
   463
  then show ?case by (cases xs) (auto, blast+)
Christian@49087
   464
qed
Christian@49087
   465
Christian@49087
   466
lemma emb_appendD:
Christian@49087
   467
  assumes "emb P (xs @ ys) zs"
Christian@49087
   468
  shows "\<exists>us vs. zs = us @ vs \<and> emb P xs us \<and> emb P ys vs"
Christian@49087
   469
using assms
Christian@49087
   470
proof (induction xs arbitrary: ys zs)
wenzelm@49107
   471
  case Nil then show ?case by auto
Christian@49087
   472
next
Christian@49087
   473
  case (Cons x xs)
Christian@49087
   474
  then obtain us v vs where "zs = us @ v # vs"
Christian@49087
   475
    and "P x v" and "emb P (xs @ ys) vs" by (auto dest: emb_ConsD)
Christian@49087
   476
  with Cons show ?case by (metis append_Cons append_assoc emb_Cons2 emb_append2)
Christian@49087
   477
qed
Christian@49087
   478
Christian@49087
   479
lemma emb_suffix:
Christian@49087
   480
  assumes "emb P xs ys" and "suffix ys zs"
Christian@49087
   481
  shows "emb P xs zs"
Christian@49087
   482
  using assms(2) and emb_append2 [OF assms(1)] by (auto simp: suffix_def)
Christian@49087
   483
Christian@49087
   484
lemma emb_suffixeq:
Christian@49087
   485
  assumes "emb P xs ys" and "suffixeq ys zs"
Christian@49087
   486
  shows "emb P xs zs"
Christian@49087
   487
  using assms and emb_suffix unfolding suffixeq_suffix_reflclp_conv by auto
Christian@49087
   488
Christian@49087
   489
lemma emb_length: "emb P xs ys \<Longrightarrow> length xs \<le> length ys"
Christian@49087
   490
  by (induct rule: emb.induct) auto
Christian@49087
   491
Christian@49087
   492
(*FIXME: move*)
wenzelm@49107
   493
definition transp_on :: "('a \<Rightarrow> 'a \<Rightarrow> bool) \<Rightarrow> 'a set \<Rightarrow> bool"
wenzelm@49107
   494
  where "transp_on P A \<longleftrightarrow> (\<forall>a\<in>A. \<forall>b\<in>A. \<forall>c\<in>A. P a b \<and> P b c \<longrightarrow> P a c)"
Christian@49087
   495
lemma transp_onI [Pure.intro]:
Christian@49087
   496
  "(\<And>a b c. \<lbrakk>a \<in> A; b \<in> A; c \<in> A; P a b; P b c\<rbrakk> \<Longrightarrow> P a c) \<Longrightarrow> transp_on P A"
Christian@49087
   497
  unfolding transp_on_def by blast
Christian@49087
   498
Christian@49087
   499
lemma transp_on_emb:
Christian@49087
   500
  assumes "transp_on P A"
Christian@49087
   501
  shows "transp_on (emb P) (lists A)"
Christian@49087
   502
proof
Christian@49087
   503
  fix xs ys zs
Christian@49087
   504
  assume "emb P xs ys" and "emb P ys zs"
Christian@49087
   505
    and "xs \<in> lists A" and "ys \<in> lists A" and "zs \<in> lists A"
wenzelm@49107
   506
  then show "emb P xs zs"
Christian@49087
   507
  proof (induction arbitrary: zs)
Christian@49087
   508
    case emb_Nil show ?case by blast
Christian@49087
   509
  next
Christian@49087
   510
    case (emb_Cons xs ys y)
Christian@49087
   511
    from emb_ConsD [OF `emb P (y#ys) zs`] obtain us v vs
Christian@49087
   512
      where zs: "zs = us @ v # vs" and "P y v" and "emb P ys vs" by blast
wenzelm@49107
   513
    then have "emb P ys (v#vs)" by blast
wenzelm@49107
   514
    then have "emb P ys zs" unfolding zs by (rule emb_append2)
Christian@49087
   515
    from emb_Cons.IH [OF this] and emb_Cons.prems show ?case by simp
Christian@49087
   516
  next
Christian@49087
   517
    case (emb_Cons2 x y xs ys)
Christian@49087
   518
    from emb_ConsD [OF `emb P (y#ys) zs`] obtain us v vs
Christian@49087
   519
      where zs: "zs = us @ v # vs" and "P y v" and "emb P ys vs" by blast
Christian@49087
   520
    with emb_Cons2 have "emb P xs vs" by simp
Christian@49087
   521
    moreover have "P x v"
Christian@49087
   522
    proof -
Christian@49087
   523
      from zs and `zs \<in> lists A` have "v \<in> A" by auto
Christian@49087
   524
      moreover have "x \<in> A" and "y \<in> A" using emb_Cons2 by simp_all
Christian@49087
   525
      ultimately show ?thesis using `P x y` and `P y v` and assms
Christian@49087
   526
        unfolding transp_on_def by blast
Christian@49087
   527
    qed
Christian@49087
   528
    ultimately have "emb P (x#xs) (v#vs)" by blast
wenzelm@49107
   529
    then show ?case unfolding zs by (rule emb_append2)
Christian@49087
   530
  qed
Christian@49087
   531
qed
Christian@49087
   532
Christian@49087
   533
Christian@49087
   534
subsection {* Sublists (special case of embedding) *}
Christian@49087
   535
wenzelm@49107
   536
abbreviation sub :: "'a list \<Rightarrow> 'a list \<Rightarrow> bool"
wenzelm@49107
   537
  where "sub xs ys \<equiv> emb (op =) xs ys"
Christian@49087
   538
Christian@49087
   539
lemma sub_Cons2: "sub xs ys \<Longrightarrow> sub (x#xs) (x#ys)" by auto
Christian@49087
   540
Christian@49087
   541
lemma sub_same_length:
Christian@49087
   542
  assumes "sub xs ys" and "length xs = length ys" shows "xs = ys"
Christian@49087
   543
  using assms by (induct) (auto dest: emb_length)
Christian@49087
   544
Christian@49087
   545
lemma not_sub_length [simp]: "length ys < length xs \<Longrightarrow> \<not> sub xs ys"
Christian@49087
   546
  by (metis emb_length linorder_not_less)
Christian@49087
   547
Christian@49087
   548
lemma [code]:
Christian@49087
   549
  "emb P [] ys \<longleftrightarrow> True"
Christian@49087
   550
  "emb P (x#xs) [] \<longleftrightarrow> False"
Christian@49087
   551
  by (simp_all)
Christian@49087
   552
Christian@49087
   553
lemma sub_Cons': "sub (x#xs) ys \<Longrightarrow> sub xs ys"
Christian@49087
   554
  by (induct xs) (auto dest: emb_ConsD)
Christian@49087
   555
Christian@49087
   556
lemma sub_Cons2':
Christian@49087
   557
  assumes "sub (x#xs) (x#ys)" shows "sub xs ys"
Christian@49087
   558
  using assms by (cases) (rule sub_Cons')
Christian@49087
   559
Christian@49087
   560
lemma sub_Cons2_neq:
Christian@49087
   561
  assumes "sub (x#xs) (y#ys)"
Christian@49087
   562
  shows "x \<noteq> y \<Longrightarrow> sub (x#xs) ys"
Christian@49087
   563
  using assms by (cases) auto
Christian@49087
   564
Christian@49087
   565
lemma sub_Cons2_iff [simp, code]:
Christian@49087
   566
  "sub (x#xs) (y#ys) = (if x = y then sub xs ys else sub (x#xs) ys)"
Christian@49087
   567
  by (metis emb_Cons emb_Cons2 [of "op =", OF refl] sub_Cons2' sub_Cons2_neq)
Christian@49087
   568
Christian@49087
   569
lemma sub_append': "sub (zs @ xs) (zs @ ys) \<longleftrightarrow> sub xs ys"
Christian@49087
   570
  by (induct zs) simp_all
Christian@49087
   571
Christian@49087
   572
lemma sub_refl [simp, intro!]: "sub xs xs" by (induct xs) simp_all
Christian@49087
   573
Christian@49087
   574
lemma sub_antisym:
Christian@49087
   575
  assumes "sub xs ys" and "sub ys xs"
Christian@49087
   576
  shows "xs = ys"
Christian@49087
   577
using assms
Christian@49087
   578
proof (induct)
Christian@49087
   579
  case emb_Nil
Christian@49087
   580
  from emb_Nil2 [OF this] show ?case by simp
Christian@49087
   581
next
wenzelm@49107
   582
  case emb_Cons2
wenzelm@49107
   583
  then show ?case by simp
Christian@49087
   584
next
wenzelm@49107
   585
  case emb_Cons
wenzelm@49107
   586
  then show ?case
Christian@49087
   587
    by (metis sub_Cons' emb_length Suc_length_conv Suc_n_not_le_n)
Christian@49087
   588
qed
Christian@49087
   589
Christian@49087
   590
lemma transp_on_sub: "transp_on sub UNIV"
Christian@49087
   591
proof -
Christian@49087
   592
  have "transp_on (op =) UNIV" by (simp add: transp_on_def)
Christian@49087
   593
  from transp_on_emb [OF this] show ?thesis by simp
Christian@49087
   594
qed
Christian@49087
   595
Christian@49087
   596
lemma sub_trans: "sub xs ys \<Longrightarrow> sub ys zs \<Longrightarrow> sub xs zs"
Christian@49087
   597
  using transp_on_sub [unfolded transp_on_def] by blast
Christian@49087
   598
Christian@49087
   599
lemma sub_append_le_same_iff: "sub (xs @ ys) ys \<longleftrightarrow> xs = []"
Christian@49087
   600
  by (auto dest: emb_length)
Christian@49087
   601
Christian@49087
   602
lemma emb_append_mono:
Christian@49087
   603
  "\<lbrakk> emb P xs xs'; emb P ys ys' \<rbrakk> \<Longrightarrow> emb P (xs@ys) (xs'@ys')"
wenzelm@49107
   604
  apply (induct rule: emb.induct)
wenzelm@49107
   605
    apply (metis eq_Nil_appendI emb_append2)
wenzelm@49107
   606
   apply (metis append_Cons emb_Cons)
wenzelm@49107
   607
  apply (metis append_Cons emb_Cons2)
wenzelm@49107
   608
  done
Christian@49087
   609
Christian@49087
   610
Christian@49087
   611
subsection {* Appending elements *}
Christian@49087
   612
Christian@49087
   613
lemma sub_append [simp]:
Christian@49087
   614
  "sub (xs @ zs) (ys @ zs) \<longleftrightarrow> sub xs ys" (is "?l = ?r")
Christian@49087
   615
proof
Christian@49087
   616
  { fix xs' ys' xs ys zs :: "'a list" assume "sub xs' ys'"
wenzelm@49107
   617
    then have "xs' = xs @ zs & ys' = ys @ zs \<longrightarrow> sub xs ys"
Christian@49087
   618
    proof (induct arbitrary: xs ys zs)
Christian@49087
   619
      case emb_Nil show ?case by simp
Christian@49087
   620
    next
Christian@49087
   621
      case (emb_Cons xs' ys' x)
wenzelm@49107
   622
      { assume "ys=[]" then have ?case using emb_Cons(1) by auto }
Christian@49087
   623
      moreover
Christian@49087
   624
      { fix us assume "ys = x#us"
wenzelm@49107
   625
        then have ?case using emb_Cons(2) by(simp add: emb.emb_Cons) }
Christian@49087
   626
      ultimately show ?case by (auto simp:Cons_eq_append_conv)
Christian@49087
   627
    next
Christian@49087
   628
      case (emb_Cons2 x y xs' ys')
wenzelm@49107
   629
      { assume "xs=[]" then have ?case using emb_Cons2(1) by auto }
Christian@49087
   630
      moreover
wenzelm@49107
   631
      { fix us vs assume "xs=x#us" "ys=x#vs" then have ?case using emb_Cons2 by auto}
Christian@49087
   632
      moreover
wenzelm@49107
   633
      { fix us assume "xs=x#us" "ys=[]" then have ?case using emb_Cons2(2) by bestsimp }
Christian@49087
   634
      ultimately show ?case using `x = y` by (auto simp: Cons_eq_append_conv)
Christian@49087
   635
    qed }
Christian@49087
   636
  moreover assume ?l
Christian@49087
   637
  ultimately show ?r by blast
Christian@49087
   638
next
wenzelm@49107
   639
  assume ?r then show ?l by (metis emb_append_mono sub_refl)
Christian@49087
   640
qed
Christian@49087
   641
Christian@49087
   642
lemma sub_drop_many: "sub xs ys \<Longrightarrow> sub xs (zs @ ys)"
Christian@49087
   643
  by (induct zs) auto
Christian@49087
   644
Christian@49087
   645
lemma sub_rev_drop_many: "sub xs ys \<Longrightarrow> sub xs (ys @ zs)"
Christian@49087
   646
  by (metis append_Nil2 emb_Nil emb_append_mono)
Christian@49087
   647
Christian@49087
   648
Christian@49087
   649
subsection {* Relation to standard list operations *}
Christian@49087
   650
Christian@49087
   651
lemma sub_map:
Christian@49087
   652
  assumes "sub xs ys" shows "sub (map f xs) (map f ys)"
Christian@49087
   653
  using assms by (induct) auto
Christian@49087
   654
Christian@49087
   655
lemma sub_filter_left [simp]: "sub (filter P xs) xs"
Christian@49087
   656
  by (induct xs) auto
Christian@49087
   657
Christian@49087
   658
lemma sub_filter [simp]:
Christian@49087
   659
  assumes "sub xs ys" shows "sub (filter P xs) (filter P ys)"
Christian@49087
   660
  using assms by (induct) auto
Christian@49087
   661
wenzelm@49107
   662
lemma "sub xs ys \<longleftrightarrow> (\<exists>N. xs = sublist ys N)" (is "?L = ?R")
Christian@49087
   663
proof
Christian@49087
   664
  assume ?L
wenzelm@49107
   665
  then show ?R
Christian@49087
   666
  proof (induct)
Christian@49087
   667
    case emb_Nil show ?case by (metis sublist_empty)
Christian@49087
   668
  next
Christian@49087
   669
    case (emb_Cons xs ys x)
Christian@49087
   670
    then obtain N where "xs = sublist ys N" by blast
wenzelm@49107
   671
    then have "xs = sublist (x#ys) (Suc ` N)"
Christian@49087
   672
      by (clarsimp simp add:sublist_Cons inj_image_mem_iff)
wenzelm@49107
   673
    then show ?case by blast
Christian@49087
   674
  next
Christian@49087
   675
    case (emb_Cons2 x y xs ys)
Christian@49087
   676
    then obtain N where "xs = sublist ys N" by blast
wenzelm@49107
   677
    then have "x#xs = sublist (x#ys) (insert 0 (Suc ` N))"
Christian@49087
   678
      by (clarsimp simp add:sublist_Cons inj_image_mem_iff)
wenzelm@49107
   679
    then show ?case unfolding `x = y` by blast
Christian@49087
   680
  qed
Christian@49087
   681
next
Christian@49087
   682
  assume ?R
Christian@49087
   683
  then obtain N where "xs = sublist ys N" ..
Christian@49087
   684
  moreover have "sub (sublist ys N) ys"
wenzelm@49107
   685
  proof (induct ys arbitrary: N)
Christian@49087
   686
    case Nil show ?case by simp
Christian@49087
   687
  next
wenzelm@49107
   688
    case Cons then show ?case by (auto simp: sublist_Cons)
Christian@49087
   689
  qed
Christian@49087
   690
  ultimately show ?L by simp
Christian@49087
   691
qed
Christian@49087
   692
wenzelm@10330
   693
end