src/hope_kv_list.erl

   1 %%%----------------------------------------------------------------------------
   2 %%% Equivalent to stdlib's orddict, but with a pretty (IMO), uniform interface.
   3 %%%----------------------------------------------------------------------------
   4 -module(hope_kv_list).
   5
   6 -behavior(hope_dictionary).
   7
   8 -export_type(
   9     [ t/2
  10     ]).
  11
  12 -export(
  13     [ empty/0
  14     , get/2
  15     , set/3
  16     , update/3
  17     , iter/2
  18     , map/2
  19     , filter/2
  20     , fold/3
  21     , of_kv_list/1
  22     , to_kv_list/1
  23     ]).
  24
  25
  26 -type t(K, V) ::
  27     [{K, V}].
  28
  29
  30 %% ============================================================================
  31 %% API
  32 %% ============================================================================
  33
  34 -spec empty() ->
  35     [].
  36 empty() ->
  37     [].
  38
  39 get(T, K) ->
  40     case lists:keyfind(K, 1, T)
  41     of  false  -> none
  42     ;   {K, V} -> {some, V}
  43     end.
  44
  45 set(T, K, V) ->
  46     lists:keystore(K, 1, T, {K, V}).
  47
  48 update(T, K, F) ->
  49     V1Opt = get(T, K),
  50     V2 = F(V1Opt),
  51     set(T, K, V2).
  52
  53 iter(T, Map1) ->
  54     Map2 = lift_map_into_list(Map1),
  55     lists:foreach(Map2, T).
  56
  57 map(T, Map1) ->
  58     Map2 = lift_map_into_list(Map1),
  59     lists:map(Map2, T).
  60
  61 filter(T, Map1) ->
  62     Map2 = lift_map_into_list(Map1),
  63     lists:filter(Map2, T).
  64
  65 fold(T, F1, Accumulator) ->
  66     F2 = fun ({K, V}, Acc) -> F1(K, V, Acc) end,
  67     lists:foldl(F2, T, Accumulator).
  68
  69 to_kv_list(T) ->
  70     T.
  71
  72 of_kv_list(List) ->
  73     List.
  74
  75
  76 %% ============================================================================
  77 %% Helpers
  78 %% ============================================================================
  79
  80 lift_map_into_list(Map) ->
  81     fun ({K, V}) -> {K, Map(K, V)} end.