src/HOL/Library/List_lexord.thy
author haftmann
Tue Mar 20 15:52:40 2007 +0100 (2007-03-20)
changeset 22483 86064f2f2188
parent 22316 f662831459de
child 22744 5cbe966d67a2
permissions -rw-r--r--
added instance for lattice
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(*  Title:      HOL/Library/List_lexord.thy
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    ID:         $Id$
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    Author:     Norbert Voelker
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*)
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header {* Lexicographic order on lists *}
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theory List_lexord
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imports Main
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begin
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instance list :: (ord) ord
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  list_le_def:  "(xs::('a::ord) list) \<le> ys \<equiv> (xs < ys \<or> xs = ys)"
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  list_less_def: "(xs::('a::ord) list) < ys \<equiv> (xs, ys) \<in> lexord {(u,v). u < v}" ..
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lemmas list_ord_defs = list_less_def list_le_def
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instance list :: (order) order
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  apply (intro_classes, unfold list_ord_defs)
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  apply safe
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  apply (rule_tac r1 = "{(a::'a,b). a < b}" in lexord_irreflexive [THEN notE])
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  apply simp
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  apply assumption
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  apply (blast intro: lexord_trans transI order_less_trans)
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  apply (rule_tac r1 = "{(a::'a,b). a < b}" in lexord_irreflexive [THEN notE])
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  apply simp
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  apply (blast intro: lexord_trans transI order_less_trans)
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  done
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instance list :: (linorder) linorder
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  apply (intro_classes, unfold list_le_def list_less_def, safe)
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  apply (cut_tac x = x and y = y and  r = "{(a,b). a < b}"  in lexord_linear)
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   apply force
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  apply simp
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  done
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instance list :: (linorder) distrib_lattice
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  "inf \<equiv> min"
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  "sup \<equiv> max"
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  by intro_classes
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    (auto simp add: inf_list_def sup_list_def min_max.sup_inf_distrib1)
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lemma not_less_Nil [simp]: "\<not> (x < [])"
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  by (unfold list_less_def) simp
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lemma Nil_less_Cons [simp]: "[] < a # x"
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  by (unfold list_less_def) simp
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lemma Cons_less_Cons [simp]: "a # x < b # y \<longleftrightarrow> a < b \<or> a = b \<and> x < y"
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  by (unfold list_less_def) simp
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lemma le_Nil [simp]: "x \<le> [] \<longleftrightarrow> x = []"
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  by (unfold list_ord_defs, cases x) auto
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lemma Nil_le_Cons [simp]: "[] \<le> x"
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  by (unfold list_ord_defs, cases x) auto
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lemma Cons_le_Cons [simp]: "a # x \<le> b # y \<longleftrightarrow> a < b \<or> a = b \<and> x \<le> y"
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  by (unfold list_ord_defs) auto
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lemma less_code [code func]:
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  "xs < ([]\<Colon>'a\<Colon>{eq, order} list) \<longleftrightarrow> False"
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  "[] < (x\<Colon>'a\<Colon>{eq, order}) # xs \<longleftrightarrow> True"
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  "(x\<Colon>'a\<Colon>{eq, order}) # xs < y # ys \<longleftrightarrow> x < y \<or> x = y \<and> xs < ys"
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  by simp_all
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lemma less_eq_code [code func]:
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  "x # xs \<le> ([]\<Colon>'a\<Colon>{eq, order} list) \<longleftrightarrow> False"
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  "[] \<le> (xs\<Colon>'a\<Colon>{eq, order} list) \<longleftrightarrow> True"
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  "(x\<Colon>'a\<Colon>{eq, order}) # xs \<le> y # ys \<longleftrightarrow> x < y \<or> x = y \<and> xs \<le> ys"
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  by simp_all
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end