A dict module lookalike that uses hamt underneath. It passes the OTP dict test

suite successfully. It's bare, no comments or specs or anything, but it works.

src/hamt_dict.erl

@@ -0,0 +1,139 @@
+%% -*- coding: utf-8 -*-
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright (C) 2013 Gregory Burd. All Rights Reserved.
+%%
+%% The contents of this file are subject to the Mozilla Public License,
+%% Version 2, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Mozilla Public License along with this software. If not, it can be
+%% retrieved online at http://www.mozilla.org/MPL/
+%%
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%%
+%% %CopyrightEnd%
+-module(hamt_dict).
+-author('Steve Vinoski <vinoski@ieee.org>').
+
+-export([append/3, append_list/3, erase/2, fetch/2,
+         fetch_keys/1, filter/2, find/2, fold/3,
+         from_list/1, is_key/2, map/2, merge/3,
+         new/0, size/1, store/3, to_list/1,
+         update/3, update/4, update_counter/3]).
+
+append(Key, Value, Dict) ->
+    NewVal = case hamt:get(Key, Dict) of
+                 {error, not_found} ->
+                     [Value];
+                 OldVal ->
+                     OldVal ++ [Value]
+             end,
+    hamt:put(Key, NewVal, Dict).
+
+append_list(Key, ValList, Dict) when is_list(ValList) ->
+    NewVal = case hamt:get(Key, Dict) of
+                 {error, not_found} ->
+                     ValList;
+                 OldVal when is_list(OldVal) ->
+                     OldVal ++ ValList;
+                 _ ->
+                     error(badarg)
+             end,
+    hamt:put(Key, NewVal, Dict).
+
+erase(Key, Dict) ->
+    hamt:delete(Key, Dict).
+
+fetch(Key, Dict) ->
+    case hamt:get(Key, Dict) of
+        {error, not_found} ->
+            error(badarg);
+        Value ->
+            Value
+    end.
+
+fetch_keys(Dict) ->
+    hamt:fold(fun(Key, _, Acc) -> [Key|Acc] end, Dict, []).
+
+filter(Pred, Dict) ->
+    Fold = fun(Key, Value, Acc) ->
+                   case Pred(Key, Value) of
+                       true ->
+                           hamt:put(Key, Value, Acc);
+                       _ ->
+                           Acc
+                   end
+           end,
+    hamt:fold(Fold, Dict, hamt:new()).
+
+find(Key, Dict) ->
+    case hamt:get(Key, Dict) of
+        {error, not_found} ->
+            error;
+        Value ->
+            {ok, Value}
+    end.
+
+fold(Fun, Acc0, Dict) ->
+    hamt:fold(Fun, Dict, Acc0).
+
+from_list(List) ->
+    hamt:from_list(List).
+
+is_key(Key, Dict) ->
+    case hamt:get(Key, Dict) of
+        {error, not_found} ->
+            false;
+        _ ->
+            true
+    end.
+
+map(Fun, Dict) ->
+    hamt:map(Fun, Dict).
+
+merge(Fun, Dict1, Dict2) ->
+    hamt:fold(fun(Key, Val1, Dict) ->
+                      update(Key, fun(Val2) -> Fun(Key, Val1, Val2) end, Val1, Dict)
+              end, Dict2, Dict1).
+
+new() ->
+    hamt:new().
+
+size(Dict) ->
+    hamt:fold(fun(_, _, Acc) -> Acc+1 end, Dict, 0).
+
+store(Key, Value, Dict) ->
+    hamt:put(Key, Value, Dict).
+
+to_list(Dict) ->
+    hamt:to_list(Dict).
+
+update(Key, Fun, Dict) ->
+    case hamt:get(Key, Dict) of
+        {error, not_found} ->
+            error(badarg);
+        Value ->
+            hamt:put(Key, Fun(Value), Dict)
+    end.
+
+update(Key, Fun, Initial, Dict) ->
+    NewVal = case hamt:get(Key, Dict) of
+                 {error, not_found} ->
+                     Initial;
+                 Value ->
+                     Fun(Value)
+             end,
+    hamt:put(Key, NewVal, Dict).
+
+update_counter(Key, Increment, Dict) ->
+    NewVal = case hamt:get(Key, Dict) of
+                 {error, not_found} ->
+                     Increment;
+                 Value ->
+                     Value+Increment
+             end,
+    hamt:put(Key, NewVal, Dict).