diff options
| -rw-r--r-- | lib/stdlib/doc/src/maps.xml | 22 | ||||
| -rw-r--r-- | lib/stdlib/src/maps.erl | 21 | ||||
| -rw-r--r-- | lib/stdlib/test/maps_SUITE.erl | 14 |
3 files changed, 50 insertions, 7 deletions
diff --git a/lib/stdlib/doc/src/maps.xml b/lib/stdlib/doc/src/maps.xml index e46068230a..7345a9357a 100644 --- a/lib/stdlib/doc/src/maps.xml +++ b/lib/stdlib/doc/src/maps.xml @@ -33,6 +33,28 @@ <funcs> <func> + <name name="filter" arity="2"/> + <fsummary>Choose pairs which satisfy a predicate</fsummary> + <desc> + <p> + Returns a map <c><anno>Map2</anno></c> for which predicate + <c><anno>Pred</anno></c> holds true in <c><anno>Map1</anno></c>. + </p> + <p> + The call will fail with a <c>{badmap,Map}</c> exception if + <c><anno>Map1</anno></c> is not a map or with <c>badarg</c> if + <c><anno>Pred</anno></c> is not a function of arity 2. + </p> + <p>Example:</p> + <code type="none"> +> M = #{a => 2, b => 3, c=> 4, "a" => 1, "b" => 2, "c" => 4}, + Pred = fun(K,V) -> is_atom(K) andalso (V rem 2) =:= 0 end, + maps:filter(Pred,M). +#{a => 2,c => 4} </code> + </desc> + </func> + + <func> <name name="find" arity="2"/> <fsummary></fsummary> <desc> diff --git a/lib/stdlib/src/maps.erl b/lib/stdlib/src/maps.erl index 3877c150ec..533ff08726 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(), @@ -169,10 +183,7 @@ fold(Fun,Init,Map) -> V2 :: term(). map(Fun,Map) when is_function(Fun, 2), is_map(Map) -> - maps:from_list(lists:map(fun - ({K,V}) -> - {K,Fun(K,V)} - end,maps:to_list(Map))); + maps:from_list([{K,Fun(K,V)}||{K,V}<-maps:to_list(Map)]); map(Fun,Map) -> erlang:error(error_type(Map),[Fun,Map]). diff --git a/lib/stdlib/test/maps_SUITE.erl b/lib/stdlib/test/maps_SUITE.erl index 1d9c041a74..21e146ae3d 100644 --- a/lib/stdlib/test/maps_SUITE.erl +++ b/lib/stdlib/test/maps_SUITE.erl @@ -34,7 +34,7 @@ -export([init_per_testcase/2]). -export([end_per_testcase/2]). --export([t_get_3/1, +-export([t_get_3/1, t_filter_2/1, t_fold_3/1,t_map_2/1,t_size_1/1, t_with_2/1,t_without_2/1]). @@ -45,7 +45,7 @@ suite() -> [{ct_hooks, [ts_install_cth]}]. all() -> - [t_get_3, + [t_get_3,t_filter_2, t_fold_3,t_map_2,t_size_1, t_with_2,t_without_2]. @@ -99,6 +99,16 @@ t_with_2(_Config) -> ?badarg(with,[a,#{}]) = (catch maps:with(a,#{})), ok. +t_filter_2(Config) when is_list(Config) -> + M = #{a => 2, b => 3, c=> 4, "a" => 1, "b" => 2, "c" => 4}, + Pred1 = fun(K,V) -> is_atom(K) andalso (V rem 2) =:= 0 end, + Pred2 = fun(K,V) -> is_list(K) andalso (V rem 2) =:= 0 end, + #{a := 2,c := 4} = maps:filter(Pred1,M), + #{"b" := 2,"c" := 4} = maps:filter(Pred2,M), + %% error case + ?badmap(a,filter,[_,a]) = (catch maps:filter(fun(_,_) -> ok end,id(a))), + ?badarg(filter,[<<>>,#{}]) = (catch maps:filter(id(<<>>),#{})), + ok. t_fold_3(Config) when is_list(Config) -> Vs = lists:seq(1,200), |