Use map generator in sets:filter/2 for version 2 sets

1 files changed, 3 insertions, 14 deletions

diff --git a/lib/stdlib/src/sets.erl b/lib/stdlib/src/sets.erl
index 816fb85a48..dccc6dcf3a 100644
--- a/lib/stdlib/src/sets.erl
+++ b/lib/stdlib/src/sets.erl
@@ -466,23 +466,12 @@ fold_1(Fun, Acc, Iter) ->
       Set1 :: set(Element),
       Set2 :: set(Element).
 filter(F, #{}=D) when is_function(F, 1)->
-    maps:from_keys(filter_1(F, maps:iterator(D)), ?VALUE);
+    %% For this purpose, it is more efficient to use
+    %% maps:from_keys than a map comprehension.
+    maps:from_keys([K || K := _ <- D, F(K)], ?VALUE);
 filter(F, #set{}=D) when is_function(F, 1)->
     filter_set(F, D).
 
-filter_1(Fun, Iter) ->
-    case maps:next(Iter) of
-        {K, _, NextIter} ->
-            case Fun(K) of
-                true ->
-                    [K | filter_1(Fun, NextIter)];
-                false ->
-                    filter_1(Fun, NextIter)
-            end;
-        none ->
-            []
-    end.
-
 %% get_slot(Hashdb, Key) -> Slot.
 %%  Get the slot.  First hash on the new range, if we hit a bucket
 %%  which has not been split use the unsplit buddy bucket.