Merge pull request #1290 from bjorng/bjorn/stdlib/take

Add take/2 to all dictionary modules

OTP-14102

1 files changed, 44 insertions, 1 deletions

diff --git a/lib/stdlib/src/gb_trees.erl b/lib/stdlib/src/gb_trees.erl
index 457287fa52..c0cdde012e 100644
--- a/lib/stdlib/src/gb_trees.erl
+++ b/lib/stdlib/src/gb_trees.erl
@@ -52,6 +52,13 @@
 %% - delete_any(X, T): removes key X from tree T if the key is present
 %%   in the tree, otherwise does nothing; returns new tree.
 %%
+%% - take(X, T): removes element with key X from tree T; returns new tree
+%%   without removed element. Assumes that the key is present in the tree.
+%%
+%% - take_any(X, T): removes element with key X from tree T and returns
+%%   a new tree if the key is present; otherwise does nothing and returns
+%%   'error'.
+%%
 %% - balance(T): rebalances tree T. Note that this is rarely necessary,
 %%   but may be motivated when a large number of entries have been
 %%   deleted from the tree without further insertions. Rebalancing could
@@ -114,7 +121,8 @@
 -export([empty/0, is_empty/1, size/1, lookup/2, get/2, insert/3,
 	 update/3, enter/3, delete/2, delete_any/2, balance/1,
 	 is_defined/2, keys/1, values/1, to_list/1, from_orddict/1,
-	 smallest/1, largest/1, take_smallest/1, take_largest/1,
+	 smallest/1, largest/1, take/2, take_any/2,
+         take_smallest/1, take_largest/1,
 	 iterator/1, iterator_from/2, next/1, map/2]).
 
 
@@ -416,6 +424,41 @@ merge(Smaller, Larger) ->
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
+-spec take_any(Key, Tree1) -> {Value, Tree2} | 'error' when
+      Tree1 :: tree(Key, _),
+      Tree2 :: tree(Key, _),
+      Key   :: term(),
+      Value :: term().
+
+take_any(Key, Tree) ->
+    case is_defined(Key, Tree) of
+        true -> take(Key, Tree);
+        false -> error
+    end.
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+-spec take(Key, Tree1) -> {Value, Tree2} when
+      Tree1 :: tree(Key, _),
+      Tree2 :: tree(Key, _),
+      Key   :: term(),
+      Value :: term().
+
+take(Key, {S, T}) when is_integer(S), S >= 0 ->
+    {Value, Res} = take_1(Key, T),
+    {Value, {S - 1, Res}}.
+
+take_1(Key, {Key1, Value, Smaller, Larger}) when Key < Key1 ->
+    {Value2, Smaller1} = take_1(Key, Smaller),
+    {Value2, {Key1, Value, Smaller1, Larger}};
+take_1(Key, {Key1, Value, Smaller, Bigger}) when Key > Key1 ->
+    {Value2, Bigger1} = take_1(Key, Bigger),
+    {Value2, {Key1, Value, Smaller, Bigger1}};
+take_1(_, {_Key, Value, Smaller, Larger}) ->
+    {Value, merge(Smaller, Larger)}.
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
 -spec take_smallest(Tree1) -> {Key, Value, Tree2} when
       Tree1 :: tree(Key, Value),
       Tree2 :: tree(Key, Value).