Merge pull request #1703 from juhlig/master

[ERL-557] add is_empty/1 to sets and ordsets
OTP-14996, ERL-557, PR-1703

7 files changed, 51 insertions, 14 deletions

diff --git a/lib/stdlib/doc/src/gb_sets.xml b/lib/stdlib/doc/src/gb_sets.xml
index 7bfe477a11..2a3785dc27 100644
--- a/lib/stdlib/doc/src/gb_sets.xml
+++ b/lib/stdlib/doc/src/gb_sets.xml
@@ -83,6 +83,8 @@
       </item>
       <item><seealso marker="#is_element/2"><c>is_element/2</c></seealso>
       </item>
+      <item><seealso marker="#is_empty/1"><c>is_empty/1</c></seealso>
+      </item>
       <item><seealso marker="#is_set/1"><c>is_set/1</c></seealso>
       </item>
       <item><seealso marker="#is_subset/2"><c>is_subset/2</c></seealso>
diff --git a/lib/stdlib/doc/src/ordsets.xml b/lib/stdlib/doc/src/ordsets.xml
index 7b590932e4..2d891d7a5a 100644
--- a/lib/stdlib/doc/src/ordsets.xml
+++ b/lib/stdlib/doc/src/ordsets.xml
@@ -142,6 +142,15 @@
     </func>
 
     <func>
+      <name name="is_empty" arity="1"/>
+      <fsummary>Test for empty set.</fsummary>
+      <desc>
+        <p>Returns <c>true</c> if <c><anno>Ordset</anno></c> is an empty set,
+          otherwise <c>false</c>.</p>
+      </desc>
+    </func>
+
+    <func>
       <name name="is_set" arity="1"/>
       <fsummary>Test for an <c>Ordset</c>.</fsummary>
       <desc>
diff --git a/lib/stdlib/doc/src/sets.xml b/lib/stdlib/doc/src/sets.xml
index 4934bed365..1ed96ddc3f 100644
--- a/lib/stdlib/doc/src/sets.xml
+++ b/lib/stdlib/doc/src/sets.xml
@@ -140,6 +140,15 @@
     </func>
 
     <func>
+      <name name="is_empty" arity="1"/>
+      <fsummary>Test for empty set.</fsummary>
+      <desc>
+        <p>Returns <c>true</c> if <c><anno>Set</anno></c> is an empty set,
+          otherwise <c>false</c>.</p>
+      </desc>
+    </func>
+
+    <func>
       <name name="is_set" arity="1"/>
       <fsummary>Test for a <c>Set</c>.</fsummary>
       <desc>
diff --git a/lib/stdlib/src/ordsets.erl b/lib/stdlib/src/ordsets.erl
index 569407f5ef..939e147ad8 100644
--- a/lib/stdlib/src/ordsets.erl
+++ b/lib/stdlib/src/ordsets.erl
@@ -19,7 +19,7 @@
 
 -module(ordsets).
 
--export([new/0,is_set/1,size/1,to_list/1,from_list/1]).
+-export([new/0,is_set/1,size/1,is_empty/1,to_list/1,from_list/1]).
 -export([is_element/2,add_element/2,del_element/2]).
 -export([union/2,union/1,intersection/2,intersection/1]).
 -export([is_disjoint/2]).
@@ -60,6 +60,13 @@ is_set([], _) -> true.
 
 size(S) -> length(S).
 
+%% is_empty(OrdSet) -> boolean().
+%%  Return 'true' if OrdSet is an empty set, otherwise 'false'.
+-spec is_empty(Ordset) -> boolean() when
+      Ordset :: ordset(_).
+
+is_empty(S) -> S=:=[].
+
 %% to_list(OrdSet) -> [Elem].
 %%  Return the elements in OrdSet as a list.
 
diff --git a/lib/stdlib/src/sets.erl b/lib/stdlib/src/sets.erl
index c65a13b22e..ac0fc80526 100644
--- a/lib/stdlib/src/sets.erl
+++ b/lib/stdlib/src/sets.erl
@@ -37,7 +37,7 @@
 -module(sets).
 
 %% Standard interface.
--export([new/0,is_set/1,size/1,to_list/1,from_list/1]).
+-export([new/0,is_set/1,size/1,is_empty/1,to_list/1,from_list/1]).
 -export([is_element/2,add_element/2,del_element/2]).
 -export([union/2,union/1,intersection/2,intersection/1]).
 -export([is_disjoint/2]).
@@ -96,6 +96,12 @@ is_set(_) -> false.
       Set :: set().
 size(S) -> S#set.size. 
 
+%% is_empty(Set) -> boolean().
+%%  Return 'true' if Set is an empty set, otherwise 'false'.
+-spec is_empty(Set) -> boolean() when
+      Set :: set().
+is_empty(S) -> S#set.size=:=0.
+
 %% to_list(Set) -> [Elem].
 %%  Return the elements in Set as a list.
 -spec to_list(Set) -> List when
diff --git a/lib/stdlib/test/sets_SUITE.erl b/lib/stdlib/test/sets_SUITE.erl
index bec38000b2..7066d07e19 100644
--- a/lib/stdlib/test/sets_SUITE.erl
+++ b/lib/stdlib/test/sets_SUITE.erl
@@ -28,7 +28,7 @@
 	 init_per_testcase/2,end_per_testcase/2,
 	 create/1,add_element/1,del_element/1,
 	 subtract/1,intersection/1,union/1,is_subset/1,
-	 is_set/1,fold/1,filter/1,
+	 is_set/1,is_empty/1,fold/1,filter/1,
 	 take_smallest/1,take_largest/1, iterate/1]).
 
 -include_lib("common_test/include/ct.hrl").
@@ -48,7 +48,7 @@ suite() ->
 all() -> 
     [create, add_element, del_element, subtract,
      intersection, union, is_subset, is_set, fold, filter,
-     take_smallest, take_largest, iterate].
+     take_smallest, take_largest, iterate, is_empty].
 
 groups() -> 
     [].
@@ -345,6 +345,17 @@ is_set_1(M) ->
     false = M(is_set, {}),
     M(empty, []).
 
+is_empty(Config) when is_list(Config) ->
+    test_all(fun is_empty_1/1).
+
+is_empty_1(M) ->
+    S = M(from_list, [blurf]),
+    Empty = M(empty, []),
+
+    true = M(is_empty, Empty),
+    false = M(is_empty, S),
+    M(empty, []).
+
 fold(Config) when is_list(Config) ->
     test_all([{0,71},{125,129},{254,259},{510,513},{1023,1025},{9999,10001}],
 	     fun fold_1/2).
diff --git a/lib/stdlib/test/sets_test_lib.erl b/lib/stdlib/test/sets_test_lib.erl
index 9f153822a2..93d027704b 100644
--- a/lib/stdlib/test/sets_test_lib.erl
+++ b/lib/stdlib/test/sets_test_lib.erl
@@ -32,7 +32,7 @@ new(Mod, Eq) ->
 	(from_list, L) -> Mod:from_list(L);
 	(intersection, {S1,S2}) -> intersection(Mod, Eq, S1, S2);
 	(intersection, Ss) -> intersection(Mod, Eq, Ss);
-	(is_empty, S) -> is_empty(Mod, S);
+	(is_empty, S) -> Mod:is_empty(S);
 	(is_set, S) -> Mod:is_set(S);
 	(is_subset, {S,Set}) -> is_subset(Mod, Eq, S, Set);
         (iterator, S) -> Mod:iterator(S);
@@ -56,7 +56,7 @@ singleton(Mod, E) ->
 add_element(Mod, El, S0) ->
     S = Mod:add_element(El, S0),
     true = Mod:is_element(El, S),
-    false = is_empty(Mod, S),
+    false = Mod:is_empty(S),
     true = Mod:is_set(S),
     S.
 
@@ -66,17 +66,10 @@ del_element(Mod, El, S0) ->
     true = Mod:is_set(S),
     S.
 
-is_empty(Mod, S) ->
-    true = Mod:is_set(S),
-    case erlang:function_exported(Mod, is_empty, 1) of
-	true -> Mod:is_empty(S);
-	false -> Mod:size(S) == 0
-    end.
-
 intersection(Mod, Equal, S1, S2) ->
     S = Mod:intersection(S1, S2),
     true = Equal(S, Mod:intersection(S2, S1)),
-    Disjoint = is_empty(Mod, S),
+    Disjoint = Mod:is_empty(S),
     Disjoint = Mod:is_disjoint(S1, S2),
     Disjoint = Mod:is_disjoint(S2, S1),
     S.