Theory Map_by_Ordered

theory Map_by_Ordered
imports AList_Upd_Del
(* Author: Tobias Nipkow *)

section {* Implementing Ordered Maps *}

theory Map_by_Ordered
imports AList_Upd_Del

locale Map =
fixes empty :: "'m"
fixes update :: "'a ⇒ 'b ⇒ 'm ⇒ 'm"
fixes delete :: "'a ⇒ 'm ⇒ 'm"
fixes lookup :: "'m ⇒ 'a ⇒ 'b option"
fixes invar :: "'m ⇒ bool"
assumes map_empty: "lookup empty = (λ_. None)"
and map_update: "invar m ⟹ lookup(update a b m) = (lookup m)(a := Some b)"
and map_delete: "invar m ⟹ lookup(delete a m) = (lookup m)(a := None)"
and invar_empty: "invar empty"
and invar_update: "invar m ⟹ invar(update a b m)"
and invar_delete: "invar m ⟹ invar(delete a m)"

locale Map_by_Ordered =
fixes empty :: "'t"
fixes update :: "'a::linorder ⇒ 'b ⇒ 't ⇒ 't"
fixes delete :: "'a ⇒ 't ⇒ 't"
fixes lookup :: "'t ⇒ 'a ⇒ 'b option"
fixes inorder :: "'t ⇒ ('a * 'b) list"
fixes inv :: "'t ⇒ bool"
assumes empty: "inorder empty = []"
and lookup: "inv t ∧ sorted1 (inorder t) ⟹
  lookup t a = map_of (inorder t) a"
and update: "inv t ∧ sorted1 (inorder t) ⟹
  inorder(update a b t) = upd_list a b (inorder t)"
and delete: "inv t ∧ sorted1 (inorder t) ⟹
  inorder(delete a t) = del_list a (inorder t)"
and inv_empty:  "inv empty"
and inv_update: "inv t ∧ sorted1 (inorder t) ⟹ inv(update a b t)"
and inv_delete: "inv t ∧ sorted1 (inorder t) ⟹ inv(delete a t)"

sublocale Map
  empty update delete lookup "λt. inv t ∧ sorted1 (inorder t)"
proof(standard, goal_cases)
  case 1 show ?case by (auto simp: lookup empty inv_empty)
  case 2 thus ?case
    by(simp add: fun_eq_iff update inv_update map_of_ins_list lookup sorted_upd_list)
  case 3 thus ?case
    by(simp add: fun_eq_iff delete inv_delete map_of_del_list lookup sorted_del_list)
  case 4 thus ?case by(simp add: empty inv_empty)
  case 5 thus ?case by(simp add: update inv_update sorted_upd_list)
  case 6 thus ?case by (auto simp: delete inv_delete sorted_del_list)