From c604ae034a79c3ca8d084de432b51af2affb2c48 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn-Egil=20Dahlberg?= <egil@erlang.org>
Date: Thu, 14 May 2015 22:10:32 +0200
Subject: stdlib: Add maps:filter/2

---
 lib/stdlib/src/maps.erl | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

(limited to 'lib/stdlib/src/maps.erl')

diff --git a/lib/stdlib/src/maps.erl b/lib/stdlib/src/maps.erl
index 3877c150ec..2913a2ff86 100644
--- a/lib/stdlib/src/maps.erl
+++ b/lib/stdlib/src/maps.erl
@@ -19,7 +19,8 @@
 
 -module(maps).
 
--export([get/3,fold/3, map/2, size/1,
+-export([get/3,filter/2,fold/3, map/2,
+         size/1,
          without/2, with/2]).
 
 
@@ -145,6 +146,19 @@ get(Key,Map,Default) ->
     erlang:error({badmap,Map},[Key,Map,Default]).
 
 
+-spec filter(Pred,Map1) -> Map2 when
+      Pred :: fun((Key, Value) -> boolean()),
+      Key  :: term(),
+      Value :: term(),
+      Map1 :: map(),
+      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)]);
+filter(Pred,Map) ->
+    erlang:error(error_type(Map),[Pred,Map]).
+
+
 -spec fold(Fun,Init,Map) -> Acc when
     Fun :: fun((K, V, AccIn) -> AccOut),
     Init :: term(),
-- 
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