--- a/UndefinedObject.st	Tue Feb 04 21:09:59 2014 +0100
+++ b/UndefinedObject.st	Wed Apr 01 10:20:10 2015 +0100
@@ -155,6 +155,8 @@
 
 
 
+
+
 !UndefinedObject methodsFor:'converting'!
 
 asBoolean
@@ -298,7 +300,6 @@
     ^ 0
 ! !
 
-
 !UndefinedObject methodsFor:'subclass creation'!
 
 nilSubclass:action
@@ -516,6 +517,17 @@
     "Modified: / 19.5.1998 / 17:39:36 / cg"
 !
 
+?+ aOneArgBlock
+     "a syntactic sugar-piece:
+      aOneArgBlock is executed with self as argument
+      if self is not nil.
+
+      Note: this method should never be redefined in classes other than UndefinedObject.
+     "
+
+    ^ self
+!
+
 ?? defaultValue
      "a syntactic sugar-piece:
       much like ?, but sends value to the argument if required.
@@ -564,7 +576,7 @@
 
      It will vanish as soon as the conversion has been done"
 
-    ^ ExternalStream openErrorSignal raise
+    ^ OpenError raise
 !
 
 hash
@@ -664,6 +676,16 @@
     "Modified: / 13.11.2001 / 13:28:15 / cg"
 !
 
+isNotNil
+    "Return true, if the receiver not nil.
+     Since I am definitely nil, unconditionally return false here.      
+     the receiver is definitely not nil here, so unconditionally return false."
+
+    ^ false
+
+    "Created: / 26-10-2014 / 01:30:15 / Jan Vrany <jan.vrany@fit.cvut.cz>"
+!
+
 notEmptyOrNil
     "Squeak compatibility:
      return true if I am neither nil nor an empty collection."
@@ -694,18 +716,20 @@
 !UndefinedObject methodsFor:'visiting'!
 
 acceptVisitor:aVisitor with:aParameter
+    "dispatch for visitor pattern; send #visitNil:with: to aVisitor."
 
     ^ aVisitor visitNilWith:aParameter
 ! !
 
+
 !UndefinedObject class methodsFor:'documentation'!
 
 version
-    ^ '$Header: /cvs/stx/stx/libbasic/UndefinedObject.st,v 1.74 2013-04-15 08:48:08 stefan Exp $'
+    ^ '$Header: /cvs/stx/stx/libbasic/UndefinedObject.st,v 1.78 2014-10-26 01:31:37 vrany Exp $'
 !
 
 version_CVS
-    ^ '$Header: /cvs/stx/stx/libbasic/UndefinedObject.st,v 1.74 2013-04-15 08:48:08 stefan Exp $'
+    ^ '$Header: /cvs/stx/stx/libbasic/UndefinedObject.st,v 1.78 2014-10-26 01:31:37 vrany Exp $'
 ! !