1(* Author: Tobias Nipkow *)
2
3section \<open>2-3 Tree Implementation of Maps\<close>
4
5theory Tree23_Map
6imports
7  Tree23_Set
8  Map_Specs
9begin
10
11fun lookup :: "('a::linorder * 'b) tree23 \<Rightarrow> 'a \<Rightarrow> 'b option" where
12"lookup Leaf x = None" |
13"lookup (Node2 l (a,b) r) x = (case cmp x a of
14  LT \<Rightarrow> lookup l x |
15  GT \<Rightarrow> lookup r x |
16  EQ \<Rightarrow> Some b)" |
17"lookup (Node3 l (a1,b1) m (a2,b2) r) x = (case cmp x a1 of
18  LT \<Rightarrow> lookup l x |
19  EQ \<Rightarrow> Some b1 |
20  GT \<Rightarrow> (case cmp x a2 of
21          LT \<Rightarrow> lookup m x |
22          EQ \<Rightarrow> Some b2 |
23          GT \<Rightarrow> lookup r x))"
24
25fun upd :: "'a::linorder \<Rightarrow> 'b \<Rightarrow> ('a*'b) tree23 \<Rightarrow> ('a*'b) up\<^sub>i" where
26"upd x y Leaf = Up\<^sub>i Leaf (x,y) Leaf" |
27"upd x y (Node2 l ab r) = (case cmp x (fst ab) of
28   LT \<Rightarrow> (case upd x y l of
29           T\<^sub>i l' => T\<^sub>i (Node2 l' ab r)
30         | Up\<^sub>i l1 ab' l2 => T\<^sub>i (Node3 l1 ab' l2 ab r)) |
31   EQ \<Rightarrow> T\<^sub>i (Node2 l (x,y) r) |
32   GT \<Rightarrow> (case upd x y r of
33           T\<^sub>i r' => T\<^sub>i (Node2 l ab r')
34         | Up\<^sub>i r1 ab' r2 => T\<^sub>i (Node3 l ab r1 ab' r2)))" |
35"upd x y (Node3 l ab1 m ab2 r) = (case cmp x (fst ab1) of
36   LT \<Rightarrow> (case upd x y l of
37           T\<^sub>i l' => T\<^sub>i (Node3 l' ab1 m ab2 r)
38         | Up\<^sub>i l1 ab' l2 => Up\<^sub>i (Node2 l1 ab' l2) ab1 (Node2 m ab2 r)) |
39   EQ \<Rightarrow> T\<^sub>i (Node3 l (x,y) m ab2 r) |
40   GT \<Rightarrow> (case cmp x (fst ab2) of
41           LT \<Rightarrow> (case upd x y m of
42                   T\<^sub>i m' => T\<^sub>i (Node3 l ab1 m' ab2 r)
43                 | Up\<^sub>i m1 ab' m2 => Up\<^sub>i (Node2 l ab1 m1) ab' (Node2 m2 ab2 r)) |
44           EQ \<Rightarrow> T\<^sub>i (Node3 l ab1 m (x,y) r) |
45           GT \<Rightarrow> (case upd x y r of
46                   T\<^sub>i r' => T\<^sub>i (Node3 l ab1 m ab2 r')
47                 | Up\<^sub>i r1 ab' r2 => Up\<^sub>i (Node2 l ab1 m) ab2 (Node2 r1 ab' r2))))"
48
49definition update :: "'a::linorder \<Rightarrow> 'b \<Rightarrow> ('a*'b) tree23 \<Rightarrow> ('a*'b) tree23" where
50"update a b t = tree\<^sub>i(upd a b t)"
51
52fun del :: "'a::linorder \<Rightarrow> ('a*'b) tree23 \<Rightarrow> ('a*'b) up\<^sub>d" where
53"del x Leaf = T\<^sub>d Leaf" |
54"del x (Node2 Leaf ab1 Leaf) = (if x=fst ab1 then Up\<^sub>d Leaf else T\<^sub>d(Node2 Leaf ab1 Leaf))" |
55"del x (Node3 Leaf ab1 Leaf ab2 Leaf) = T\<^sub>d(if x=fst ab1 then Node2 Leaf ab2 Leaf
56  else if x=fst ab2 then Node2 Leaf ab1 Leaf else Node3 Leaf ab1 Leaf ab2 Leaf)" |
57"del x (Node2 l ab1 r) = (case cmp x (fst ab1) of
58  LT \<Rightarrow> node21 (del x l) ab1 r |
59  GT \<Rightarrow> node22 l ab1 (del x r) |
60  EQ \<Rightarrow> let (ab1',t) = split_min r in node22 l ab1' t)" |
61"del x (Node3 l ab1 m ab2 r) = (case cmp x (fst ab1) of
62  LT \<Rightarrow> node31 (del x l) ab1 m ab2 r |
63  EQ \<Rightarrow> let (ab1',m') = split_min m in node32 l ab1' m' ab2 r |
64  GT \<Rightarrow> (case cmp x (fst ab2) of
65           LT \<Rightarrow> node32 l ab1 (del x m) ab2 r |
66           EQ \<Rightarrow> let (ab2',r') = split_min r in node33 l ab1 m ab2' r' |
67           GT \<Rightarrow> node33 l ab1 m ab2 (del x r)))"
68
69definition delete :: "'a::linorder \<Rightarrow> ('a*'b) tree23 \<Rightarrow> ('a*'b) tree23" where
70"delete x t = tree\<^sub>d(del x t)"
71
72
73subsection \<open>Functional Correctness\<close>
74
75lemma lookup_map_of:
76  "sorted1(inorder t) \<Longrightarrow> lookup t x = map_of (inorder t) x"
77by (induction t) (auto simp: map_of_simps split: option.split)
78
79
80lemma inorder_upd:
81  "sorted1(inorder t) \<Longrightarrow> inorder(tree\<^sub>i(upd x y t)) = upd_list x y (inorder t)"
82by(induction t) (auto simp: upd_list_simps split: up\<^sub>i.splits)
83
84corollary inorder_update:
85  "sorted1(inorder t) \<Longrightarrow> inorder(update x y t) = upd_list x y (inorder t)"
86by(simp add: update_def inorder_upd)
87
88
89lemma inorder_del: "\<lbrakk> bal t ; sorted1(inorder t) \<rbrakk> \<Longrightarrow>
90  inorder(tree\<^sub>d (del x t)) = del_list x (inorder t)"
91by(induction t rule: del.induct)
92  (auto simp: del_list_simps inorder_nodes split_minD split!: if_split prod.splits)
93
94corollary inorder_delete: "\<lbrakk> bal t ; sorted1(inorder t) \<rbrakk> \<Longrightarrow>
95  inorder(delete x t) = del_list x (inorder t)"
96by(simp add: delete_def inorder_del)
97
98
99subsection \<open>Balancedness\<close>
100
101lemma bal_upd: "bal t \<Longrightarrow> bal (tree\<^sub>i(upd x y t)) \<and> height(upd x y t) = height t"
102by (induct t) (auto split!: if_split up\<^sub>i.split)(* 16 secs in 2015 *)
103
104corollary bal_update: "bal t \<Longrightarrow> bal (update x y t)"
105by (simp add: update_def bal_upd)
106
107
108lemma height_del: "bal t \<Longrightarrow> height(del x t) = height t"
109by(induction x t rule: del.induct)
110  (auto simp add: heights max_def height_split_min split: prod.split)
111
112lemma bal_tree\<^sub>d_del: "bal t \<Longrightarrow> bal(tree\<^sub>d(del x t))"
113by(induction x t rule: del.induct)
114  (auto simp: bals bal_split_min height_del height_split_min split: prod.split)
115
116corollary bal_delete: "bal t \<Longrightarrow> bal(delete x t)"
117by(simp add: delete_def bal_tree\<^sub>d_del)
118
119
120subsection \<open>Overall Correctness\<close>
121
122interpretation M: Map_by_Ordered
123where empty = empty and lookup = lookup and update = update and delete = delete
124and inorder = inorder and inv = bal
125proof (standard, goal_cases)
126  case 1 thus ?case by(simp add: empty_def)
127next
128  case 2 thus ?case by(simp add: lookup_map_of)
129next
130  case 3 thus ?case by(simp add: inorder_update)
131next
132  case 4 thus ?case by(simp add: inorder_delete)
133next
134  case 5 thus ?case by(simp add: empty_def)
135next
136  case 6 thus ?case by(simp add: bal_update)
137next
138  case 7 thus ?case by(simp add: bal_delete)
139qed
140
141end
142