Implement a Key->Value list dictionary.

diff --git a/src/hope_kv_list.erl b/src/hope_kv_list.erl
new file mode 100644 (file)
index 0000000..0b80a4a
--- /dev/null
+++ b/src/hope_kv_list.erl
@@ -0,0 +1,81 @@
+%%%----------------------------------------------------------------------------
+%%% Equivalent to stdlib's orddict, but with a pretty (IMO), uniform interface.
+%%%----------------------------------------------------------------------------
+-module(hope_kv_list).
+
+-behavior(hope_dictionary).
+
+-export_type(
+    [ t/2
+    ]).
+
+-export(
+    [ empty/0
+    , get/2
+    , set/3
+    , update/3
+    , iter/2
+    , map/2
+    , filter/2
+    , fold/3
+    , of_kv_list/1
+    , to_kv_list/1
+    ]).
+
+
+-type t(K, V) ::
+    [{K, V}].
+
+
+%% ============================================================================
+%% API
+%% ============================================================================
+
+-spec empty() ->
+    [].
+empty() ->
+    [].
+
+get(T, K) ->
+    case lists:keyfind(K, 1, T)
+    of  false  -> none
+    ;   {K, V} -> {some, V}
+    end.
+
+set(T, K, V) ->
+    lists:keystore(K, 1, T, {K, V}).
+
+update(T, K, F) ->
+    V1Opt = get(T, K),
+    V2 = F(V1Opt),
+    set(T, K, V2).
+
+iter(T, Map1) ->
+    Map2 = lift_map_into_list(Map1),
+    lists:foreach(Map2, T).
+
+map(T, Map1) ->
+    Map2 = lift_map_into_list(Map1),
+    lists:map(Map2, T).
+
+filter(T, Map1) ->
+    Map2 = lift_map_into_list(Map1),
+    lists:filter(Map2, T).
+
+fold(T, F1, Accumulator) ->
+    F2 = fun ({K, V}, Acc) -> F1(K, V, Acc) end,
+    lists:foldl(F2, T, Accumulator).
+
+to_kv_list(T) ->
+    T.
+
+of_kv_list(List) ->
+    List.
+
+
+%% ============================================================================
+%% Helpers
+%% ============================================================================
+
+lift_map_into_list(Map) ->
+    fun ({K, V}) -> {K, Map(K, V)} end.