remove class_eval on slots to map registers

Use their class names (or for now called object names)
these are the same that Register helper functions accept already anyway

lib/virtual/slots/frame_slot.rb

@@ -7,6 +7,10 @@ module Virtual
     def initialize type = Unknown, value = nil
       super
     end
+
+    def object_name
+      return :frame
+    end
   end
 
 end

lib/virtual/slots/message_slot.rb

@@ -10,6 +10,9 @@ module Virtual
     def initialize type = Unknown , value = nil
       super(type , value )
     end
+    def object_name
+      :message
+    end
   end
 
   # named classes exist for slots that often accessed

lib/virtual/slots/next_message_slot.rb

@@ -10,6 +10,9 @@ module Virtual
     def initialize type = Unknown, value = nil
       super( type , value )
     end
+    def object_name
+      :new_message
+    end
   end
 
   # named classes exist for slots that often accessed

lib/virtual/slots/self_slot.rb

@@ -17,5 +17,8 @@ module Virtual
     def initialize type = Unknown, value = nil
       super
     end
+    def object_name
+      :self
+    end
   end
 end

lib/virtual/slots/slot.rb

@@ -18,6 +18,13 @@ module Virtual
 
   class Slot < Object
 
+    # the name of the object of a slot is a symbol that represents what the class name describes
+    # ie it is one of :message , :self , :frame , :new_message
+    # one of the objects the machine works on. 
+    def object_name
+      raise "abstract called #{self}"
+    end
+
     attr_accessor :type , :value
 
     private #abstract base class