diff options
| -rw-r--r-- | lib/stdlib/doc/src/maps.xml | 27 | ||||
| -rw-r--r-- | lib/stdlib/src/maps.erl | 30 | ||||
| -rw-r--r-- | lib/stdlib/test/maps_SUITE.erl | 18 |
3 files changed, 72 insertions, 3 deletions
diff --git a/lib/stdlib/doc/src/maps.xml b/lib/stdlib/doc/src/maps.xml index aba390af7f..d04b34b32b 100644 --- a/lib/stdlib/doc/src/maps.xml +++ b/lib/stdlib/doc/src/maps.xml @@ -73,6 +73,33 @@ </func> <func> + <name name="filtermap" arity="2" since=""/> + <fsummary>Filter and map a map.</fsummary> + <desc> + <p>Returns a map <c><anno>Map</anno></c> that is the result of calling + <c><anno>Fun</anno>(<anno>Key</anno>, <anno>Value1</anno>)</c> for + every <c><anno>Key</anno></c> to value <c><anno>Value1</anno></c> + association in <c><anno>MapOrIter</anno></c> in any order.</p> + <p>If <c><anno>Fun</anno>(<anno>Key</anno>, <anno>Value1</anno>)</c> + returns <c>true</c>, the association is copied to the result map. If + it returns <c>false</c>, the association is not copied. If it returns + <c>{true, NewValue}</c>, the value for <c><anno>Key</anno></c> is + replaced with <c>NewValue</c>at this position is replaced in the + result map.</p> + <p>The call fails with a <c>{badmap,Map}</c> exception if + <c><anno>MapOrIter</anno></c> is not a map or valid iterator, + or with <c>badarg</c> if <c><anno>Fun</anno></c> is not a + function of arity 3.</p> + <p><em>Example:</em></p> + <code type="none"> +> Fun = fun(K,V) when is_atom(K) -> {true, V*2}; (_,V) -> (V rem 2) =:= 0 end, + Map = #{k1 => 1, "k2" => 2, "k3" => 3}, + maps:filtermap(Fun,Map). +#{k1 => 2,"k2" => 2}</code> + </desc> + </func> + + <func> <name name="find" arity="2" since="OTP 17.0"/> <fsummary></fsummary> <desc> diff --git a/lib/stdlib/src/maps.erl b/lib/stdlib/src/maps.erl index 1f2b774eb9..8d94f6d430 100644 --- a/lib/stdlib/src/maps.erl +++ b/lib/stdlib/src/maps.erl @@ -20,7 +20,7 @@ -module(maps). --export([get/3, filter/2,fold/3, +-export([get/3, filter/2, filtermap/2, fold/3, map/2, size/1, new/0, update_with/3, update_with/4, without/2, with/2, @@ -305,6 +305,34 @@ filter_1(Pred, Iter) -> [] end. + +-spec filtermap(Fun, MapOrIter) -> Map when + Fun :: fun((Key, Value1) -> boolean() | {true, Value2}), + MapOrIter :: #{Key => Value1} | iterator(Key, Value1), + Map :: #{Key => Value1 | Value2}. + +filtermap(Fun, Map) when is_function(Fun, 2), is_map(Map) -> + maps:from_list(filtermap_1(Fun, iterator(Map))); +filtermap(Fun, Iterator) when is_function(Fun, 2), ?IS_ITERATOR(Iterator) -> + maps:from_list(filtermap_1(Fun, Iterator)); +filtermap(Fun, Map) -> + erlang:error(error_type(Map), [Fun, Map]). + +filtermap_1(Pred, Iter) -> + case next(Iter) of + {K, V, NextIter} -> + case Pred(K, V) of + true -> + [{K, V} | filtermap_1(Pred, NextIter)]; + {true, NewV} -> + [{K, NewV} | filtermap_1(Pred, NextIter)]; + false -> + filtermap_1(Pred, NextIter) + end; + none -> + [] + end. + -spec fold(Fun,Init,MapOrIter) -> Acc when Fun :: fun((Key, Value, AccIn) -> AccOut), Init :: term(), diff --git a/lib/stdlib/test/maps_SUITE.erl b/lib/stdlib/test/maps_SUITE.erl index 3d5b0d7465..451b1b54e9 100644 --- a/lib/stdlib/test/maps_SUITE.erl +++ b/lib/stdlib/test/maps_SUITE.erl @@ -28,7 +28,7 @@ -export([all/0, suite/0]). -export([t_update_with_3/1, t_update_with_4/1, - t_get_3/1, t_filter_2/1, + t_get_3/1, t_filter_2/1, t_filtermap_2/1, t_fold_3/1,t_map_2/1,t_size_1/1, t_iterator_1/1, t_put_opt/1, t_merge_opt/1, t_with_2/1,t_without_2/1, @@ -45,7 +45,7 @@ suite() -> all() -> [t_update_with_3,t_update_with_4, - t_get_3,t_filter_2, + t_get_3,t_filter_2,t_filtermap_2, t_fold_3,t_map_2,t_size_1, t_iterator_1,t_put_opt,t_merge_opt, t_with_2,t_without_2, @@ -141,6 +141,20 @@ t_filter_2(Config) when is_list(Config) -> ?badarg(filter,[<<>>,#{}]) = (catch maps:filter(id(<<>>),#{})), ok. +t_filtermap_2(Config) when is_list(Config) -> + M0 = maps:from_list([{I, I} || I <- lists:seq(1, 30)]), + Pred = fun(K,_) when K=<10 -> true; (K,_) when K=<20 -> false; (_,V) -> {true, V * V} end, + M1 = maps:filtermap(Pred, M0), + M2 = maps:filtermap(Pred, maps:iterator(M0)), + #{1 := 1, 10 := 10, 21 := 21 * 21, 30 := 30 * 30} = M1, + false = maps:is_key(11, M1), + false = maps:is_key(20, M1), + true = M1 =:= M2, + %% error case + ?badmap(a,filtermap,[_,a]) = (catch maps:filtermap(fun(_,_) -> ok end,id(a))), + ?badarg(filtermap,[<<>>,#{}]) = (catch maps:filtermap(id(<<>>),#{})), + ok. + t_fold_3(Config) when is_list(Config) -> Vs = lists:seq(1,200), M0 = maps:from_list([{{k,I},I}||I<-Vs]), |