(* Author: Tobias Nipkow *)
section {* Implementing Ordered Maps *}
theory Map_by_Ordered
imports AList_Upd_Del
begin
locale Map =
fixes empty :: "'m"
fixes update :: "'a \<Rightarrow> 'b \<Rightarrow> 'm \<Rightarrow> 'm"
fixes delete :: "'a \<Rightarrow> 'm \<Rightarrow> 'm"
fixes lookup :: "'m \<Rightarrow> 'a \<Rightarrow> 'b option"
fixes invar :: "'m \<Rightarrow> bool"
assumes map_empty: "lookup empty = (\<lambda>_. None)"
and map_update: "invar m \<Longrightarrow> lookup(update a b m) = (lookup m)(a := Some b)"
and map_delete: "invar m \<Longrightarrow> lookup(delete a m) = (lookup m)(a := None)"
and invar_empty: "invar empty"
and invar_update: "invar m \<Longrightarrow> invar(update a b m)"
and invar_delete: "invar m \<Longrightarrow> invar(delete a m)"
locale Map_by_Ordered =
fixes empty :: "'t"
fixes update :: "'a::linorder \<Rightarrow> 'b \<Rightarrow> 't \<Rightarrow> 't"
fixes delete :: "'a \<Rightarrow> 't \<Rightarrow> 't"
fixes lookup :: "'t \<Rightarrow> 'a \<Rightarrow> 'b option"
fixes inorder :: "'t \<Rightarrow> ('a * 'b) list"
fixes inv :: "'t \<Rightarrow> bool"
assumes empty: "inorder empty = []"
and lookup: "inv t \<and> sorted1 (inorder t) \<Longrightarrow>
lookup t a = map_of (inorder t) a"
and update: "inv t \<and> sorted1 (inorder t) \<Longrightarrow>
inorder(update a b t) = upd_list a b (inorder t)"
and delete: "inv t \<and> sorted1 (inorder t) \<Longrightarrow>
inorder(delete a t) = del_list a (inorder t)"
and inv_empty: "inv empty"
and inv_update: "inv t \<and> sorted1 (inorder t) \<Longrightarrow> inv(update a b t)"
and inv_delete: "inv t \<and> sorted1 (inorder t) \<Longrightarrow> inv(delete a t)"
begin
sublocale Map
empty update delete lookup "\<lambda>t. inv t \<and> sorted1 (inorder t)"
proof(standard, goal_cases)
case 1 show ?case by (auto simp: lookup empty inv_empty)
next
case 2 thus ?case
by(simp add: fun_eq_iff update inv_update map_of_ins_list lookup sorted_upd_list)
next
case 3 thus ?case
by(simp add: fun_eq_iff delete inv_delete map_of_del_list lookup sorted_del_list)
next
case 4 thus ?case by(simp add: empty inv_empty)
next
case 5 thus ?case by(simp add: update inv_update sorted_upd_list)
next
case 6 thus ?case by (auto simp: delete inv_delete sorted_del_list)
qed
end
end