* lib/set.rb (Set#delete_if, Set#keep_if): Add comments.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40827 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,7 @@
+Sun May 19 17:29:07 2013  Akinori MUSHA  <knu@iDaemons.org>
+
+	* lib/set.rb (Set#delete_if, Set#keep_if): Add comments.
+
 Sun May 19 11:37:36 2013  Kazuki Tsujimoto  <kazuki@callcc.net>
 
 	* ext/fiddle/extconf.rb: ignore rc version of libffi to fix build failure.

lib/set.rb

@@ -272,6 +272,8 @@ class Set
   # true, and returns self.
   def delete_if
     block_given? or return enum_for(__method__)
+    # @hash.delete_if should be faster, but using it breaks the order
+    # of enumeration in subclasses.
     select(&proc).each(&@hash.method(:delete))
     self
   end
@@ -280,6 +282,8 @@ class Set
   # false, and returns self.
   def keep_if
     block_given? or return enum_for(__method__)
+    # @hash.keep_if should be faster, but using it breaks the order of
+    # enumeration in subclasses.
     reject(&proc).each(&@hash.method(:delete))
     self
   end