File 2723-Add-maps-filtermap-2.patch of Package erlang
From 12c1200dc83f51d0cfe055b7fec449152af7530d Mon Sep 17 00:00:00 2001
From: Maria-12648430 <maria-12648430@gmx.net>
Date: Tue, 1 Dec 2020 15:39:14 +0100
Subject: [PATCH] Add maps:filtermap/2
---
lib/stdlib/doc/src/maps.xml | 27 +++++++++++++++++++++++++++
lib/stdlib/src/maps.erl | 30 +++++++++++++++++++++++++++++-
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
@@ -72,6 +72,33 @@
</desc>
</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>
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]),
--
2.26.2
