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authorLukas Larsson <[email protected]>2017-09-19 12:01:09 +0200
committerLukas Larsson <[email protected]>2017-10-13 15:44:33 +0200
commitd945d6f1c71d5442a25e4be60f84fc49ae8b6b4e (patch)
tree689ced6362e563341f5f37d6a5862054a7a8e6b1 /lib
parent264738bfb75de9f11defe51753ba5a0599154bd0 (diff)
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stdlib: Introduce maps iterator API
Diffstat (limited to 'lib')
-rw-r--r--lib/stdlib/src/maps.erl76
1 files changed, 62 insertions, 14 deletions
diff --git a/lib/stdlib/src/maps.erl b/lib/stdlib/src/maps.erl
index 5dafdb282a..7ed32a3988 100644
--- a/lib/stdlib/src/maps.erl
+++ b/lib/stdlib/src/maps.erl
@@ -23,7 +23,8 @@
-export([get/3, filter/2,fold/3,
map/2, size/1,
update_with/3, update_with/4,
- without/2, with/2]).
+ without/2, with/2,
+ iterator/1, next/1]).
%% BIFs
-export([get/2, find/2, from_list/1,
@@ -31,6 +32,10 @@
new/0, put/3, remove/2, take/2,
to_list/1, update/3, values/1]).
+-opaque iterator() :: [{term(), term()}].
+
+-export_type([iterator/0]).
+
%% Shadowed by erl_bif_types: maps:get/2
-spec get(Key,Map) -> Value when
Key :: term(),
@@ -200,10 +205,22 @@ get(Key,Map,Default) ->
Map2 :: map().
filter(Pred,Map) when is_function(Pred,2), is_map(Map) ->
- maps:from_list([{K,V}||{K,V}<-maps:to_list(Map),Pred(K,V)]);
+ maps:from_list(filter_1(Pred, iterator(Map)));
filter(Pred,Map) ->
erlang:error(error_type(Map),[Pred,Map]).
+filter_1(Pred, Iter) ->
+ case next(Iter) of
+ {K, V, NextIter} ->
+ case Pred(K,V) of
+ true ->
+ [{K,V} | filter_1(Pred, NextIter)];
+ false ->
+ filter_1(Pred, NextIter)
+ end;
+ none ->
+ []
+ end.
-spec fold(Fun,Init,Map) -> Acc when
Fun :: fun((K, V, AccIn) -> AccOut),
@@ -216,10 +233,18 @@ filter(Pred,Map) ->
V :: term().
fold(Fun,Init,Map) when is_function(Fun,3), is_map(Map) ->
- lists:foldl(fun({K,V},A) -> Fun(K,V,A) end,Init,maps:to_list(Map));
+ fold_1(Fun, Init, iterator(Map));
fold(Fun,Init,Map) ->
erlang:error(error_type(Map),[Fun,Init,Map]).
+fold_1(Fun, Acc, Iter) ->
+ case next(Iter) of
+ {K, V, NextIter} ->
+ fold_1(Fun, Fun(K,V,Acc), NextIter);
+ none ->
+ Acc
+ end.
+
-spec map(Fun,Map1) -> Map2 when
Fun :: fun((K, V1) -> V2),
Map1 :: map(),
@@ -229,10 +254,17 @@ fold(Fun,Init,Map) ->
V2 :: term().
map(Fun,Map) when is_function(Fun, 2), is_map(Map) ->
- maps:from_list([{K,Fun(K,V)}||{K,V}<-maps:to_list(Map)]);
+ maps:from_list(map_1(Fun, iterator(Map)));
map(Fun,Map) ->
erlang:error(error_type(Map),[Fun,Map]).
+map_1(Fun, Iter) ->
+ case next(Iter) of
+ {K, V, NextIter} ->
+ [{K, Fun(K, V)} | map_1(Fun, NextIter)];
+ none ->
+ []
+ end.
-spec size(Map) -> non_neg_integer() when
Map :: map().
@@ -242,6 +274,23 @@ size(Map) when is_map(Map) ->
size(Val) ->
erlang:error({badmap,Val},[Val]).
+-spec iterator(Map) -> Iterator when
+ Map :: map(),
+ Iterator :: iterator().
+
+iterator(Map) when is_map(Map) ->
+ maps:to_list(Map);
+iterator(M) ->
+ erlang:error(error_type(M),[M]).
+
+-spec next(Iterator) -> {K,V,NextIterator} | 'none' when
+ Iterator :: iterator(),
+ K :: term(),
+ V :: term(),
+ NextIterator :: iterator().
+next([]) -> none;
+next([{K, V} | I]) ->
+ {K, V, I}.
-spec without(Ks,Map1) -> Map2 when
Ks :: [K],
@@ -250,11 +299,10 @@ size(Val) ->
K :: term().
without(Ks,M) when is_list(Ks), is_map(M) ->
- lists:foldl(fun(K, M1) -> ?MODULE:remove(K, M1) end, M, Ks);
+ lists:foldl(fun(K, M1) -> maps:remove(K, M1) end, M, Ks);
without(Ks,M) ->
erlang:error(error_type(M),[Ks,M]).
-
-spec with(Ks, Map1) -> Map2 when
Ks :: [K],
Map1 :: map(),
@@ -263,14 +311,14 @@ without(Ks,M) ->
with(Ks,Map1) when is_list(Ks), is_map(Map1) ->
Fun = fun(K, List) ->
- case ?MODULE:find(K, Map1) of
- {ok, V} ->
- [{K, V} | List];
- error ->
- List
- end
- end,
- ?MODULE:from_list(lists:foldl(Fun, [], Ks));
+ case maps:find(K, Map1) of
+ {ok, V} ->
+ [{K, V} | List];
+ error ->
+ List
+ end
+ end,
+ maps:from_list(lists:foldl(Fun, [], Ks));
with(Ks,M) ->
erlang:error(error_type(M),[Ks,M]).