42 (case cmp x a of |
42 (case cmp x a of |
43 LT \<Rightarrow> Node (delete x l) a r | |
43 LT \<Rightarrow> Node (delete x l) a r | |
44 GT \<Rightarrow> Node l a (delete x r) | |
44 GT \<Rightarrow> Node l a (delete x r) | |
45 EQ \<Rightarrow> if r = Leaf then l else let (a',r') = split_min r in Node l a' r')" |
45 EQ \<Rightarrow> if r = Leaf then l else let (a',r') = split_min r in Node l a' r')" |
46 |
46 |
47 text \<open>Deletion by appending:\<close> |
47 text \<open>Deletion by joining:\<close> |
48 |
48 |
49 fun app :: "('a::linorder)tree \<Rightarrow> 'a tree \<Rightarrow> 'a tree" where |
49 fun join :: "('a::linorder)tree \<Rightarrow> 'a tree \<Rightarrow> 'a tree" where |
50 "app t Leaf = t" | |
50 "join t Leaf = t" | |
51 "app Leaf t = t" | |
51 "join Leaf t = t" | |
52 "app (Node t1 a t2) (Node t3 b t4) = |
52 "join (Node t1 a t2) (Node t3 b t4) = |
53 (case app t2 t3 of |
53 (case join t2 t3 of |
54 Leaf \<Rightarrow> Node t1 a (Node Leaf b t4) | |
54 Leaf \<Rightarrow> Node t1 a (Node Leaf b t4) | |
55 Node u2 x u3 \<Rightarrow> Node (Node t1 a u2) x (Node u3 b t4))" |
55 Node u2 x u3 \<Rightarrow> Node (Node t1 a u2) x (Node u3 b t4))" |
56 |
56 |
57 fun delete2 :: "'a::linorder \<Rightarrow> 'a tree \<Rightarrow> 'a tree" where |
57 fun delete2 :: "'a::linorder \<Rightarrow> 'a tree \<Rightarrow> 'a tree" where |
58 "delete2 x Leaf = Leaf" | |
58 "delete2 x Leaf = Leaf" | |
59 "delete2 x (Node l a r) = |
59 "delete2 x (Node l a r) = |
60 (case cmp x a of |
60 (case cmp x a of |
61 LT \<Rightarrow> Node (delete2 x l) a r | |
61 LT \<Rightarrow> Node (delete2 x l) a r | |
62 GT \<Rightarrow> Node l a (delete2 x r) | |
62 GT \<Rightarrow> Node l a (delete2 x r) | |
63 EQ \<Rightarrow> app l r)" |
63 EQ \<Rightarrow> join l r)" |
64 |
64 |
65 |
65 |
66 subsection "Functional Correctness Proofs" |
66 subsection "Functional Correctness Proofs" |
67 |
67 |
68 lemma isin_set: "sorted(inorder t) \<Longrightarrow> isin t x = (x \<in> set (inorder t))" |
68 lemma isin_set: "sorted(inorder t) \<Longrightarrow> isin t x = (x \<in> set (inorder t))" |
93 case 3 thus ?case by(simp add: inorder_insert) |
93 case 3 thus ?case by(simp add: inorder_insert) |
94 next |
94 next |
95 case 4 thus ?case by(simp add: inorder_delete) |
95 case 4 thus ?case by(simp add: inorder_delete) |
96 qed (rule TrueI)+ |
96 qed (rule TrueI)+ |
97 |
97 |
98 lemma inorder_app: |
98 lemma inorder_join: |
99 "inorder(app l r) = inorder l @ inorder r" |
99 "inorder(join l r) = inorder l @ inorder r" |
100 by(induction l r rule: app.induct) (auto split: tree.split) |
100 by(induction l r rule: join.induct) (auto split: tree.split) |
101 |
101 |
102 lemma inorder_delete2: |
102 lemma inorder_delete2: |
103 "sorted(inorder t) \<Longrightarrow> inorder(delete2 x t) = del_list x (inorder t)" |
103 "sorted(inorder t) \<Longrightarrow> inorder(delete2 x t) = del_list x (inorder t)" |
104 by(induction t) (auto simp: inorder_app del_list_simps) |
104 by(induction t) (auto simp: inorder_join del_list_simps) |
105 |
105 |
106 interpretation S2: Set_by_Ordered |
106 interpretation S2: Set_by_Ordered |
107 where empty = empty and isin = isin and insert = insert and delete = delete2 |
107 where empty = empty and isin = isin and insert = insert and delete = delete2 |
108 and inorder = inorder and inv = "\<lambda>_. True" |
108 and inorder = inorder and inv = "\<lambda>_. True" |
109 proof (standard, goal_cases) |
109 proof (standard, goal_cases) |