src/HOL/Data_Structures/Brother12_Set.thy
author nipkow
Tue Jun 12 17:18:40 2018 +0200 (13 months ago)
changeset 68431 b294e095f64c
parent 68020 6aade817bee5
permissions -rw-r--r--
more abstract naming
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(* Author: Tobias Nipkow, Daniel Stüwe *)
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section \<open>1-2 Brother Tree Implementation of Sets\<close>
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theory Brother12_Set
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imports
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  Cmp
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  Set_Specs
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  "HOL-Number_Theory.Fib"
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begin
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subsection \<open>Data Type and Operations\<close>
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datatype 'a bro =
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  N0 |
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  N1 "'a bro" |
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  N2 "'a bro" 'a "'a bro" |
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  (* auxiliary constructors: *)
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  L2 'a |
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  N3 "'a bro" 'a "'a bro" 'a "'a bro"
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definition empty :: "'a bro" where
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"empty = N0"
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fun inorder :: "'a bro \<Rightarrow> 'a list" where
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"inorder N0 = []" |
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"inorder (N1 t) = inorder t" |
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"inorder (N2 l a r) = inorder l @ a # inorder r" |
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"inorder (L2 a) = [a]" |
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"inorder (N3 t1 a1 t2 a2 t3) = inorder t1 @ a1 # inorder t2 @ a2 # inorder t3"
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fun isin :: "'a bro \<Rightarrow> 'a::linorder \<Rightarrow> bool" where
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"isin N0 x = False" |
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"isin (N1 t) x = isin t x" |
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"isin (N2 l a r) x =
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  (case cmp x a of
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     LT \<Rightarrow> isin l x |
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     EQ \<Rightarrow> True |
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     GT \<Rightarrow> isin r x)"
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fun n1 :: "'a bro \<Rightarrow> 'a bro" where
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"n1 (L2 a) = N2 N0 a N0" |
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"n1 (N3 t1 a1 t2 a2 t3) = N2 (N2 t1 a1 t2) a2 (N1 t3)" |
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"n1 t = N1 t"
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hide_const (open) insert
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locale insert
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begin
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fun n2 :: "'a bro \<Rightarrow> 'a \<Rightarrow> 'a bro \<Rightarrow> 'a bro" where
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"n2 (L2 a1) a2 t = N3 N0 a1 N0 a2 t" |
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"n2 (N3 t1 a1 t2 a2 t3) a3 (N1 t4) = N2 (N2 t1 a1 t2) a2 (N2 t3 a3 t4)" |
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"n2 (N3 t1 a1 t2 a2 t3) a3 t4 = N3 (N2 t1 a1 t2) a2 (N1 t3) a3 t4" |
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"n2 t1 a1 (L2 a2) = N3 t1 a1 N0 a2 N0" |
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"n2 (N1 t1) a1 (N3 t2 a2 t3 a3 t4) = N2 (N2 t1 a1 t2) a2 (N2 t3 a3 t4)" |
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"n2 t1 a1 (N3 t2 a2 t3 a3 t4) = N3 t1 a1 (N1 t2) a2 (N2 t3 a3 t4)" |
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"n2 t1 a t2 = N2 t1 a t2"
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fun ins :: "'a::linorder \<Rightarrow> 'a bro \<Rightarrow> 'a bro" where
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"ins x N0 = L2 x" |
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"ins x (N1 t) = n1 (ins x t)" |
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"ins x (N2 l a r) =
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  (case cmp x a of
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     LT \<Rightarrow> n2 (ins x l) a r |
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     EQ \<Rightarrow> N2 l a r |
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     GT \<Rightarrow> n2 l a (ins x r))"
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fun tree :: "'a bro \<Rightarrow> 'a bro" where
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"tree (L2 a) = N2 N0 a N0" |
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"tree (N3 t1 a1 t2 a2 t3) = N2 (N2 t1 a1 t2) a2 (N1 t3)" |
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"tree t = t"
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definition insert :: "'a::linorder \<Rightarrow> 'a bro \<Rightarrow> 'a bro" where
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"insert x t = tree(ins x t)"
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end
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locale delete
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begin
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fun n2 :: "'a bro \<Rightarrow> 'a \<Rightarrow> 'a bro \<Rightarrow> 'a bro" where
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"n2 (N1 t1) a1 (N1 t2) = N1 (N2 t1 a1 t2)" |
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"n2 (N1 (N1 t1)) a1 (N2 (N1 t2) a2 (N2 t3 a3 t4)) =
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  N1 (N2 (N2 t1 a1 t2) a2 (N2 t3 a3 t4))" |
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"n2 (N1 (N1 t1)) a1 (N2 (N2 t2 a2 t3) a3 (N1 t4)) =
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  N1 (N2 (N2 t1 a1 t2) a2 (N2 t3 a3 t4))" |
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"n2 (N1 (N1 t1)) a1 (N2 (N2 t2 a2 t3) a3 (N2 t4 a4 t5)) =
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  N2 (N2 (N1 t1) a1 (N2 t2 a2 t3)) a3 (N1 (N2 t4 a4 t5))" |
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"n2 (N2 (N1 t1) a1 (N2 t2 a2 t3)) a3 (N1 (N1 t4)) =
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  N1 (N2 (N2 t1 a1 t2) a2 (N2 t3 a3 t4))" |
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"n2 (N2 (N2 t1 a1 t2) a2 (N1 t3)) a3 (N1 (N1 t4)) =
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  N1 (N2 (N2 t1 a1 t2) a2 (N2 t3 a3 t4))" |
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"n2 (N2 (N2 t1 a1 t2) a2 (N2 t3 a3 t4)) a5 (N1 (N1 t5)) =
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  N2 (N1 (N2 t1 a1 t2)) a2 (N2 (N2 t3 a3 t4) a5 (N1 t5))" |
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"n2 t1 a1 t2 = N2 t1 a1 t2"
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fun split_min :: "'a bro \<Rightarrow> ('a \<times> 'a bro) option" where
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"split_min N0 = None" |
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"split_min (N1 t) =
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  (case split_min t of
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     None \<Rightarrow> None |
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     Some (a, t') \<Rightarrow> Some (a, N1 t'))" |
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"split_min (N2 t1 a t2) =
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  (case split_min t1 of
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     None \<Rightarrow> Some (a, N1 t2) |
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     Some (b, t1') \<Rightarrow> Some (b, n2 t1' a t2))"
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fun del :: "'a::linorder \<Rightarrow> 'a bro \<Rightarrow> 'a bro" where
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"del _ N0         = N0" |
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"del x (N1 t)     = N1 (del x t)" |
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"del x (N2 l a r) =
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  (case cmp x a of
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     LT \<Rightarrow> n2 (del x l) a r |
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     GT \<Rightarrow> n2 l a (del x r) |
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     EQ \<Rightarrow> (case split_min r of
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              None \<Rightarrow> N1 l |
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              Some (b, r') \<Rightarrow> n2 l b r'))"
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fun tree :: "'a bro \<Rightarrow> 'a bro" where
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"tree (N1 t) = t" |
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"tree t = t"
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definition delete :: "'a::linorder \<Rightarrow> 'a bro \<Rightarrow> 'a bro" where
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"delete a t = tree (del a t)"
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end
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subsection \<open>Invariants\<close>
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fun B :: "nat \<Rightarrow> 'a bro set"
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and U :: "nat \<Rightarrow> 'a bro set" where
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"B 0 = {N0}" |
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"B (Suc h) = { N2 t1 a t2 | t1 a t2. 
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  t1 \<in> B h \<union> U h \<and> t2 \<in> B h \<or> t1 \<in> B h \<and> t2 \<in> B h \<union> U h}" |
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"U 0 = {}" |
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"U (Suc h) = N1 ` B h"
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abbreviation "T h \<equiv> B h \<union> U h"
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fun Bp :: "nat \<Rightarrow> 'a bro set" where
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"Bp 0 = B 0 \<union> L2 ` UNIV" |
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"Bp (Suc 0) = B (Suc 0) \<union> {N3 N0 a N0 b N0|a b. True}" |
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"Bp (Suc(Suc h)) = B (Suc(Suc h)) \<union>
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  {N3 t1 a t2 b t3 | t1 a t2 b t3. t1 \<in> B (Suc h) \<and> t2 \<in> U (Suc h) \<and> t3 \<in> B (Suc h)}"
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fun Um :: "nat \<Rightarrow> 'a bro set" where
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"Um 0 = {}" |
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"Um (Suc h) = N1 ` T h"
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subsection "Functional Correctness Proofs"
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subsubsection "Proofs for isin"
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lemma isin_set:
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  "t \<in> T h \<Longrightarrow> sorted(inorder t) \<Longrightarrow> isin t x = (x \<in> set(inorder t))"
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by(induction h arbitrary: t) (fastforce simp: isin_simps split: if_splits)+
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subsubsection "Proofs for insertion"
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lemma inorder_n1: "inorder(n1 t) = inorder t"
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by(cases t rule: n1.cases) (auto simp: sorted_lems)
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context insert
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begin
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lemma inorder_n2: "inorder(n2 l a r) = inorder l @ a # inorder r"
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by(cases "(l,a,r)" rule: n2.cases) (auto simp: sorted_lems)
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lemma inorder_tree: "inorder(tree t) = inorder t"
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by(cases t) auto
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lemma inorder_ins: "t \<in> T h \<Longrightarrow>
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  sorted(inorder t) \<Longrightarrow> inorder(ins a t) = ins_list a (inorder t)"
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by(induction h arbitrary: t) (auto simp: ins_list_simps inorder_n1 inorder_n2)
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lemma inorder_insert: "t \<in> T h \<Longrightarrow>
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  sorted(inorder t) \<Longrightarrow> inorder(insert a t) = ins_list a (inorder t)"
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by(simp add: insert_def inorder_ins inorder_tree)
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end
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subsubsection \<open>Proofs for deletion\<close>
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context delete
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begin
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lemma inorder_tree: "inorder(tree t) = inorder t"
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by(cases t) auto
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lemma inorder_n2: "inorder(n2 l a r) = inorder l @ a # inorder r"
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by(cases "(l,a,r)" rule: n2.cases) (auto)
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lemma inorder_split_min:
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  "t \<in> T h \<Longrightarrow> (split_min t = None \<longleftrightarrow> inorder t = []) \<and>
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  (split_min t = Some(a,t') \<longrightarrow> inorder t = a # inorder t')"
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by(induction h arbitrary: t a t') (auto simp: inorder_n2 split: option.splits)
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lemma inorder_del:
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  "t \<in> T h \<Longrightarrow> sorted(inorder t) \<Longrightarrow> inorder(del x t) = del_list x (inorder t)"
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by(induction h arbitrary: t) (auto simp: del_list_simps inorder_n2
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     inorder_split_min[OF UnI1] inorder_split_min[OF UnI2] split: option.splits)
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lemma inorder_delete:
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  "t \<in> T h \<Longrightarrow> sorted(inorder t) \<Longrightarrow> inorder(delete x t) = del_list x (inorder t)"
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by(simp add: delete_def inorder_del inorder_tree)
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end
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subsection \<open>Invariant Proofs\<close>
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subsubsection \<open>Proofs for insertion\<close>
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lemma n1_type: "t \<in> Bp h \<Longrightarrow> n1 t \<in> T (Suc h)"
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by(cases h rule: Bp.cases) auto
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context insert
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begin
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lemma tree_type: "t \<in> Bp h \<Longrightarrow> tree t \<in> B h \<union> B (Suc h)"
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by(cases h rule: Bp.cases) auto
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lemma n2_type:
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  "(t1 \<in> Bp h \<and> t2 \<in> T h \<longrightarrow> n2 t1 a t2 \<in> Bp (Suc h)) \<and>
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   (t1 \<in> T h \<and> t2 \<in> Bp h \<longrightarrow> n2 t1 a t2 \<in> Bp (Suc h))"
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apply(cases h rule: Bp.cases)
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apply (auto)[2]
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apply(rule conjI impI | erule conjE exE imageE | simp | erule disjE)+
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done
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lemma Bp_if_B: "t \<in> B h \<Longrightarrow> t \<in> Bp h"
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by (cases h rule: Bp.cases) simp_all
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text\<open>An automatic proof:\<close>
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lemma
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  "(t \<in> B h \<longrightarrow> ins x t \<in> Bp h) \<and> (t \<in> U h \<longrightarrow> ins x t \<in> T h)"
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apply(induction h arbitrary: t)
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 apply (simp)
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apply (fastforce simp: Bp_if_B n2_type dest: n1_type)
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done
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text\<open>A detailed proof:\<close>
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lemma ins_type:
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shows "t \<in> B h \<Longrightarrow> ins x t \<in> Bp h" and "t \<in> U h \<Longrightarrow> ins x t \<in> T h"
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proof(induction h arbitrary: t)
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  case 0
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  { case 1 thus ?case by simp
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  next
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    case 2 thus ?case by simp }
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next
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  case (Suc h)
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  { case 1
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    then obtain t1 a t2 where [simp]: "t = N2 t1 a t2" and
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      t1: "t1 \<in> T h" and t2: "t2 \<in> T h" and t12: "t1 \<in> B h \<or> t2 \<in> B h"
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      by auto
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    have ?case if "x < a"
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    proof -
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      have "n2 (ins x t1) a t2 \<in> Bp (Suc h)"
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      proof cases
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        assume "t1 \<in> B h"
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        with t2 show ?thesis by (simp add: Suc.IH(1) n2_type)
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      next
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        assume "t1 \<notin> B h"
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        hence 1: "t1 \<in> U h" and 2: "t2 \<in> B h" using t1 t12 by auto
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        show ?thesis by (metis Suc.IH(2)[OF 1] Bp_if_B[OF 2] n2_type)
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      qed
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      with \<open>x < a\<close> show ?case by simp
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    qed
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    moreover
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    have ?case if "a < x"
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    proof -
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      have "n2 t1 a (ins x t2) \<in> Bp (Suc h)"
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      proof cases
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        assume "t2 \<in> B h"
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        with t1 show ?thesis by (simp add: Suc.IH(1) n2_type)
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      next
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        assume "t2 \<notin> B h"
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        hence 1: "t1 \<in> B h" and 2: "t2 \<in> U h" using t2 t12 by auto
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        show ?thesis by (metis Bp_if_B[OF 1] Suc.IH(2)[OF 2] n2_type)
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      qed
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      with \<open>a < x\<close> show ?case by simp
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    qed
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    moreover
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    have ?case if "x = a"
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    proof -
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      from 1 have "t \<in> Bp (Suc h)" by(rule Bp_if_B)
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      thus "?case" using \<open>x = a\<close> by simp
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    qed
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    ultimately show ?case by auto
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  next
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    case 2 thus ?case using Suc(1) n1_type by fastforce }
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qed
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lemma insert_type:
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  "t \<in> B h \<Longrightarrow> insert x t \<in> B h \<union> B (Suc h)"
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unfolding insert_def by (metis ins_type(1) tree_type)
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end
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subsubsection "Proofs for deletion"
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lemma B_simps[simp]: 
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  "N1 t \<in> B h = False"
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  "L2 y \<in> B h = False"
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  "(N3 t1 a1 t2 a2 t3) \<in> B h = False"
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  "N0 \<in> B h \<longleftrightarrow> h = 0"
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by (cases h, auto)+
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context delete
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begin
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lemma n2_type1:
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  "\<lbrakk>t1 \<in> Um h; t2 \<in> B h\<rbrakk> \<Longrightarrow> n2 t1 a t2 \<in> T (Suc h)"
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apply(cases h rule: Bp.cases)
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   319
apply auto[2]
nipkow@61784
   320
apply(erule exE bexE conjE imageE | simp | erule disjE)+
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   321
done
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   322
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   323
lemma n2_type2:
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   324
  "\<lbrakk>t1 \<in> B h ; t2 \<in> Um h \<rbrakk> \<Longrightarrow> n2 t1 a t2 \<in> T (Suc h)"
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   325
apply(cases h rule: Bp.cases)
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   326
apply auto[2]
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   327
apply(erule exE bexE conjE imageE | simp | erule disjE)+
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   328
done
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   329
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   330
lemma n2_type3:
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   331
  "\<lbrakk>t1 \<in> T h ; t2 \<in> T h \<rbrakk> \<Longrightarrow> n2 t1 a t2 \<in> T (Suc h)"
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   332
apply(cases h rule: Bp.cases)
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   333
apply auto[2]
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   334
apply(erule exE bexE conjE imageE | simp | erule disjE)+
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   335
done
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   336
nipkow@68020
   337
lemma split_minNoneN0: "\<lbrakk>t \<in> B h; split_min t = None\<rbrakk> \<Longrightarrow>  t = N0"
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   338
by (cases t) (auto split: option.splits)
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   339
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   340
lemma split_minNoneN1 : "\<lbrakk>t \<in> U h; split_min t = None\<rbrakk> \<Longrightarrow> t = N1 N0"
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   341
by (cases h) (auto simp: split_minNoneN0  split: option.splits)
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   342
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   343
lemma split_min_type:
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   344
  "t \<in> B h \<Longrightarrow> split_min t = Some (a, t') \<Longrightarrow> t' \<in> T h"
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   345
  "t \<in> U h \<Longrightarrow> split_min t = Some (a, t') \<Longrightarrow> t' \<in> Um h"
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   346
proof (induction h arbitrary: t a t')
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   347
  case (Suc h)
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   348
  { case 1
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   349
    then obtain t1 a t2 where [simp]: "t = N2 t1 a t2" and
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   350
      t12: "t1 \<in> T h" "t2 \<in> T h" "t1 \<in> B h \<or> t2 \<in> B h"
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   351
      by auto
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   352
    show ?case
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   353
    proof (cases "split_min t1")
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   354
      case None
nipkow@61784
   355
      show ?thesis
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   356
      proof cases
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   357
        assume "t1 \<in> B h"
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   358
        with split_minNoneN0[OF this None] 1 show ?thesis by(auto)
nipkow@61784
   359
      next
nipkow@61784
   360
        assume "t1 \<notin> B h"
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   361
        thus ?thesis using 1 None by (auto)
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   362
      qed
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   363
    next
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   364
      case [simp]: (Some bt')
nipkow@61784
   365
      obtain b t1' where [simp]: "bt' = (b,t1')" by fastforce
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   366
      show ?thesis
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   367
      proof cases
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   368
        assume "t1 \<in> B h"
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   369
        from Suc.IH(1)[OF this] 1 have "t1' \<in> T h" by simp
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   370
        from n2_type3[OF this t12(2)] 1 show ?thesis by auto
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   371
      next
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   372
        assume "t1 \<notin> B h"
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   373
        hence t1: "t1 \<in> U h" and t2: "t2 \<in> B h" using t12 by auto
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   374
        from Suc.IH(2)[OF t1] have "t1' \<in> Um h" by simp
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   375
        from n2_type1[OF this t2] 1 show ?thesis by auto
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   376
      qed
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   377
    qed
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   378
  }
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   379
  { case 2
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   380
    then obtain t1 where [simp]: "t = N1 t1" and t1: "t1 \<in> B h" by auto
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   381
    show ?case
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   382
    proof (cases "split_min t1")
nipkow@61784
   383
      case None
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   384
      with split_minNoneN0[OF t1 None] 2 show ?thesis by(auto)
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   385
    next
nipkow@61784
   386
      case [simp]: (Some bt')
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   387
      obtain b t1' where [simp]: "bt' = (b,t1')" by fastforce
nipkow@61784
   388
      from Suc.IH(1)[OF t1] have "t1' \<in> T h" by simp
nipkow@61784
   389
      thus ?thesis using 2 by auto
nipkow@61784
   390
    qed
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   391
  }
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   392
qed auto
nipkow@61784
   393
nipkow@61784
   394
lemma del_type:
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   395
  "t \<in> B h \<Longrightarrow> del x t \<in> T h"
nipkow@61784
   396
  "t \<in> U h \<Longrightarrow> del x t \<in> Um h"
nipkow@61784
   397
proof (induction h arbitrary: x t)
nipkow@61784
   398
  case (Suc h)
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   399
  { case 1
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   400
    then obtain l a r where [simp]: "t = N2 l a r" and
nipkow@61784
   401
      lr: "l \<in> T h" "r \<in> T h" "l \<in> B h \<or> r \<in> B h" by auto
nipkow@67040
   402
    have ?case if "x < a"
nipkow@67040
   403
    proof cases
nipkow@67040
   404
      assume "l \<in> B h"
nipkow@67040
   405
      from n2_type3[OF Suc.IH(1)[OF this] lr(2)]
wenzelm@67406
   406
      show ?thesis using \<open>x<a\<close> by(simp)
nipkow@67040
   407
    next
nipkow@67040
   408
      assume "l \<notin> B h"
nipkow@67040
   409
      hence "l \<in> U h" "r \<in> B h" using lr by auto
nipkow@67040
   410
      from n2_type1[OF Suc.IH(2)[OF this(1)] this(2)]
wenzelm@67406
   411
      show ?thesis using \<open>x<a\<close> by(simp)
nipkow@67040
   412
    qed
nipkow@67040
   413
    moreover
nipkow@67040
   414
    have ?case if "x > a"
nipkow@67040
   415
    proof cases
nipkow@67040
   416
      assume "r \<in> B h"
nipkow@67040
   417
      from n2_type3[OF lr(1) Suc.IH(1)[OF this]]
wenzelm@67406
   418
      show ?thesis using \<open>x>a\<close> by(simp)
nipkow@67040
   419
    next
nipkow@67040
   420
      assume "r \<notin> B h"
nipkow@67040
   421
      hence "l \<in> B h" "r \<in> U h" using lr by auto
nipkow@67040
   422
      from n2_type2[OF this(1) Suc.IH(2)[OF this(2)]]
wenzelm@67406
   423
      show ?thesis using \<open>x>a\<close> by(simp)
nipkow@67040
   424
    qed
nipkow@67040
   425
    moreover
nipkow@67040
   426
    have ?case if [simp]: "x=a"
nipkow@68020
   427
    proof (cases "split_min r")
nipkow@67040
   428
      case None
nipkow@67040
   429
      show ?thesis
nipkow@61784
   430
      proof cases
nipkow@61784
   431
        assume "r \<in> B h"
nipkow@68020
   432
        with split_minNoneN0[OF this None] lr show ?thesis by(simp)
nipkow@61784
   433
      next
nipkow@61784
   434
        assume "r \<notin> B h"
nipkow@67040
   435
        hence "r \<in> U h" using lr by auto
nipkow@68020
   436
        with split_minNoneN1[OF this None] lr(3) show ?thesis by (simp)
nipkow@61784
   437
      qed
nipkow@67040
   438
    next
nipkow@67040
   439
      case [simp]: (Some br')
nipkow@67040
   440
      obtain b r' where [simp]: "br' = (b,r')" by fastforce
nipkow@67040
   441
      show ?thesis
nipkow@67040
   442
      proof cases
nipkow@67040
   443
        assume "r \<in> B h"
nipkow@68020
   444
        from split_min_type(1)[OF this] n2_type3[OF lr(1)]
nipkow@67040
   445
        show ?thesis by simp
nipkow@61784
   446
      next
nipkow@67040
   447
        assume "r \<notin> B h"
nipkow@67040
   448
        hence "l \<in> B h" and "r \<in> U h" using lr by auto
nipkow@68020
   449
        from split_min_type(2)[OF this(2)] n2_type2[OF this(1)]
nipkow@67040
   450
        show ?thesis by simp
nipkow@61784
   451
      qed
nipkow@67040
   452
    qed
nipkow@67040
   453
    ultimately show ?case by auto
nipkow@61784
   454
  }
nipkow@61784
   455
  { case 2 with Suc.IH(1) show ?case by auto }
nipkow@61784
   456
qed auto
nipkow@61784
   457
wenzelm@67613
   458
lemma tree_type: "t \<in> T (h+1) \<Longrightarrow> tree t \<in> B (h+1) \<union> B h"
nipkow@61784
   459
by(auto)
nipkow@61784
   460
nipkow@61809
   461
lemma delete_type: "t \<in> B h \<Longrightarrow> delete x t \<in> B h \<union> B(h-1)"
nipkow@61784
   462
unfolding delete_def
nipkow@61809
   463
by (cases h) (simp, metis del_type(1) tree_type Suc_eq_plus1 diff_Suc_1)
nipkow@61784
   464
nipkow@61784
   465
end
nipkow@61784
   466
nipkow@61789
   467
nipkow@61784
   468
subsection "Overall correctness"
nipkow@61784
   469
nipkow@61784
   470
interpretation Set_by_Ordered
nipkow@68431
   471
where empty = empty and isin = isin and insert = insert.insert
nipkow@61809
   472
and delete = delete.delete and inorder = inorder and inv = "\<lambda>t. \<exists>h. t \<in> B h"
nipkow@61784
   473
proof (standard, goal_cases)
nipkow@61784
   474
  case 2 thus ?case by(auto intro!: isin_set)
nipkow@61784
   475
next
nipkow@61784
   476
  case 3 thus ?case by(auto intro!: insert.inorder_insert)
nipkow@61784
   477
next
nipkow@61792
   478
  case 4 thus ?case by(auto intro!: delete.inorder_delete)
nipkow@61784
   479
next
nipkow@61784
   480
  case 6 thus ?case using insert.insert_type by blast
nipkow@61784
   481
next
nipkow@61784
   482
  case 7 thus ?case using delete.delete_type by blast
nipkow@68431
   483
qed (auto simp: empty_def)
nipkow@61784
   484
nipkow@63411
   485
nipkow@63411
   486
subsection \<open>Height-Size Relation\<close>
nipkow@63411
   487
nipkow@63411
   488
text \<open>By Daniel St\"uwe\<close>
nipkow@63411
   489
nipkow@63411
   490
fun fib_tree :: "nat \<Rightarrow> unit bro" where
nipkow@63411
   491
  "fib_tree 0 = N0" 
nipkow@63411
   492
| "fib_tree (Suc 0) = N2 N0 () N0"
nipkow@63411
   493
| "fib_tree (Suc(Suc h)) = N2 (fib_tree (h+1)) () (N1 (fib_tree h))"
nipkow@63411
   494
nipkow@63411
   495
fun fib' :: "nat \<Rightarrow> nat" where
nipkow@63411
   496
  "fib' 0 = 0" 
nipkow@63411
   497
| "fib' (Suc 0) = 1"
nipkow@63411
   498
| "fib' (Suc(Suc h)) = 1 + fib' (Suc h) + fib' h"
nipkow@63411
   499
nipkow@63411
   500
fun size :: "'a bro \<Rightarrow> nat" where
nipkow@63411
   501
  "size N0 = 0" 
nipkow@63411
   502
| "size (N1 t) = size t"
nipkow@63411
   503
| "size (N2 t1 _ t2) = 1 + size t1 + size t2"
nipkow@63411
   504
nipkow@63411
   505
lemma fib_tree_B: "fib_tree h \<in> B h"
nipkow@63411
   506
by (induction h rule: fib_tree.induct) auto
nipkow@63411
   507
nipkow@63411
   508
declare [[names_short]]
nipkow@63411
   509
nipkow@63411
   510
lemma size_fib': "size (fib_tree h) = fib' h"
nipkow@63411
   511
by (induction h rule: fib_tree.induct) auto
nipkow@63411
   512
nipkow@63411
   513
lemma fibfib: "fib' h + 1 = fib (Suc(Suc h))"
nipkow@63411
   514
by (induction h rule: fib_tree.induct) auto
nipkow@63411
   515
nipkow@63411
   516
lemma B_N2_cases[consumes 1]:
nipkow@63411
   517
assumes "N2 t1 a t2 \<in> B (Suc n)"
nipkow@63411
   518
obtains 
nipkow@63411
   519
  (BB) "t1 \<in> B n" and "t2 \<in> B n" |
nipkow@63411
   520
  (UB) "t1 \<in> U n" and "t2 \<in> B n" |
nipkow@63411
   521
  (BU) "t1 \<in> B n" and "t2 \<in> U n"
nipkow@63411
   522
using assms by auto
nipkow@63411
   523
nipkow@63411
   524
lemma size_bounded: "t \<in> B h \<Longrightarrow> size t \<ge> size (fib_tree h)"
nipkow@63411
   525
unfolding size_fib' proof (induction h arbitrary: t rule: fib'.induct)
nipkow@63411
   526
case (3 h t')
nipkow@63411
   527
  note main = 3
nipkow@63411
   528
  then obtain t1 a t2 where t': "t' = N2 t1 a t2" by auto
nipkow@63411
   529
  with main have "N2 t1 a t2 \<in> B (Suc (Suc h))" by auto
nipkow@63411
   530
  thus ?case proof (cases rule: B_N2_cases)
nipkow@63411
   531
    case BB
nipkow@63411
   532
    then obtain x y z where t2: "t2 = N2 x y z \<or> t2 = N2 z y x" "x \<in> B h" by auto
nipkow@63411
   533
    show ?thesis unfolding t' using main(1)[OF BB(1)] main(2)[OF t2(2)] t2(1) by auto
nipkow@63411
   534
  next
nipkow@63411
   535
    case UB
nipkow@63411
   536
    then obtain t11 where t1: "t1 = N1 t11" "t11 \<in> B h" by auto
nipkow@63411
   537
    show ?thesis unfolding t' t1(1) using main(2)[OF t1(2)] main(1)[OF UB(2)] by simp
nipkow@63411
   538
  next
nipkow@63411
   539
    case BU
nipkow@63411
   540
    then obtain t22 where t2: "t2 = N1 t22" "t22 \<in> B h" by auto
nipkow@63411
   541
    show ?thesis unfolding t' t2(1) using main(2)[OF t2(2)] main(1)[OF BU(1)] by simp
nipkow@63411
   542
  qed
nipkow@63411
   543
qed auto
nipkow@63411
   544
nipkow@63411
   545
theorem "t \<in> B h \<Longrightarrow> fib (h + 2) \<le> size t + 1"
nipkow@63411
   546
using size_bounded
nipkow@63411
   547
by (simp add: size_fib' fibfib[symmetric] del: fib.simps)
nipkow@63411
   548
nipkow@61784
   549
end