Just another update

Task/Null-object/C++/null-object-3.cpp

@@ -1,5 +1,9 @@
 int *p = nullptr;
 ...
-if(p == nullptr){
+if (p == nullptr){
+  // do some thing
+}
+//or just
+if (p){
   // do some thing
 }

Task/Null-object/Eiffel/null-object.e

@@ -0,0 +1,22 @@
+class
+	APPLICATION
+inherit
+	ARGUMENTS
+create
+	make
+
+feature {NONE} -- Initialization
+
+	make
+		local
+			i: INTEGER
+			s: detachable STRING
+		do
+			if i = Void then
+				print("i = Void")
+			end
+			if s = Void then
+				print("s = Void")
+			end
+		end
+end

Task/Null-object/Ruby/null-object.rb

@@ -1 +1,7 @@
-   puts "object is null" if object.nil?
+puts "@object is nil" if @object.nil?		# instance variable
+
+puts "$object is nil" if $object.nil?		# global variable, too
+
+# It recognizes as the local variable even if it isn't executed.
+object = 1  if false
+puts "object is nil" if object.nil?