src/HOL/Library/AList_Mapping.thy

tuned;

(* Title: HOL/Library/AList_Mapping.thy
   Author: Florian Haftmann, TU Muenchen
*)

section \<open>Implementation of mappings with Association Lists\<close>

theory AList_Mapping
imports AList Mapping
begin

lift_definition Mapping :: "('a \<times> 'b) list \<Rightarrow> ('a, 'b) mapping" is map_of .

code_datatype Mapping

lemma lookup_Mapping [simp, code]:
  "Mapping.lookup (Mapping xs) = map_of xs"
  by transfer rule

lemma keys_Mapping [simp, code]:
  "Mapping.keys (Mapping xs) = set (map fst xs)" 
  by transfer (simp add: dom_map_of_conv_image_fst)

lemma empty_Mapping [code]:
  "Mapping.empty = Mapping []"
  by transfer simp

lemma is_empty_Mapping [code]:
  "Mapping.is_empty (Mapping xs) \<longleftrightarrow> List.null xs"
  by (case_tac xs) (simp_all add: is_empty_def null_def)

lemma update_Mapping [code]:
  "Mapping.update k v (Mapping xs) = Mapping (AList.update k v xs)"
  by transfer (simp add: update_conv')

lemma delete_Mapping [code]:
  "Mapping.delete k (Mapping xs) = Mapping (AList.delete k xs)"
  by transfer (simp add: delete_conv')

lemma ordered_keys_Mapping [code]:
  "Mapping.ordered_keys (Mapping xs) = sort (remdups (map fst xs))"
  by (simp only: ordered_keys_def keys_Mapping sorted_list_of_set_sort_remdups) simp

lemma size_Mapping [code]:
  "Mapping.size (Mapping xs) = length (remdups (map fst xs))"
  by (simp add: size_def length_remdups_card_conv dom_map_of_conv_image_fst)

lemma tabulate_Mapping [code]:
  "Mapping.tabulate ks f = Mapping (map (\<lambda>k. (k, f k)) ks)"
  by transfer (simp add: map_of_map_restrict)

lemma bulkload_Mapping [code]:
  "Mapping.bulkload vs = Mapping (map (\<lambda>n. (n, vs ! n)) [0..<length vs])"
  by transfer (simp add: map_of_map_restrict fun_eq_iff)

lemma equal_Mapping [code]:
  "HOL.equal (Mapping xs) (Mapping ys) \<longleftrightarrow>
    (let ks = map fst xs; ls = map fst ys
    in (\<forall>l\<in>set ls. l \<in> set ks) \<and> (\<forall>k\<in>set ks. k \<in> set ls \<and> map_of xs k = map_of ys k))"
proof -
  have aux: "\<And>a b xs. (a, b) \<in> set xs \<Longrightarrow> a \<in> fst ` set xs"
    by (auto simp add: image_def intro!: bexI)
  show ?thesis apply transfer
    by (auto intro!: map_of_eqI) (auto dest!: map_of_eq_dom intro: aux)
qed

lemma map_values_Mapping [code]:
  fixes f :: "'c \<Rightarrow> 'a \<Rightarrow> 'b" and xs :: "('c \<times> 'a) list"
  shows "Mapping.map_values f (Mapping xs) = Mapping (map (\<lambda>(x,y). (x, f x y)) xs)"
proof (transfer, rule ext, goal_cases)
  case (1 f xs x)
  thus ?case by (induction xs) auto
qed

lemma combine_with_key_code [code]: 
  "Mapping.combine_with_key f (Mapping xs) (Mapping ys) =
     Mapping.tabulate (remdups (map fst xs @ map fst ys)) 
       (\<lambda>x. the (combine_options (f x) (map_of xs x) (map_of ys x)))"
proof (transfer, rule ext, rule sym, goal_cases)
  case (1 f xs ys x)
  show ?case
  by (cases "map_of xs x"; cases "map_of ys x"; simp)
     (force simp: map_of_eq_None_iff combine_options_def option.the_def o_def image_iff
            dest: map_of_SomeD split: option.splits)+
qed

lemma combine_code [code]: 
  "Mapping.combine f (Mapping xs) (Mapping ys) =
     Mapping.tabulate (remdups (map fst xs @ map fst ys)) 
       (\<lambda>x. the (combine_options f (map_of xs x) (map_of ys x)))"
proof (transfer, rule ext, rule sym, goal_cases)
  case (1 f xs ys x)
  show ?case
  by (cases "map_of xs x"; cases "map_of ys x"; simp)
     (force simp: map_of_eq_None_iff combine_options_def option.the_def o_def image_iff
            dest: map_of_SomeD split: option.splits)+
qed

(* TODO: Move? *)
lemma map_of_filter_distinct:
  assumes "distinct (map fst xs)"
  shows   "map_of (filter P xs) x = 
             (case map_of xs x of None \<Rightarrow> None | Some y \<Rightarrow> if P (x,y) then Some y else None)"
  using assms
  by (auto simp: map_of_eq_None_iff filter_map distinct_map_filter dest: map_of_SomeD
           simp del: map_of_eq_Some_iff intro!: map_of_is_SomeI split: option.splits)
(* END TODO *)
  
lemma filter_Mapping [code]:
  "Mapping.filter P (Mapping xs) = Mapping (filter (\<lambda>(k,v). P k v) (AList.clearjunk xs))"
 by (transfer, rule ext)
    (subst map_of_filter_distinct, simp_all add: map_of_clearjunk split: option.split)

lemma [code nbe]:
  "HOL.equal (x :: ('a, 'b) mapping) x \<longleftrightarrow> True"
  by (fact equal_refl)

end