fold last of the virtual into register

lib/register/positioned.rb

@@ -0,0 +1,20 @@
+#require_relative "type"
+
+module Positioned
+  def position
+    if @position.nil?
+      str = "IN machine #{Register.machine.objects.has_key?(self.object_id)}, at #{self.object_id.to_s(16)}\n"
+      raise str + "position not set for #{self.class} len #{word_length} for #{self.inspect[0...100]}"
+    end
+    @position
+  end
+  def set_position pos
+    raise "Setting of nil not allowed" if pos.nil?
+    # resetting of position used to be error, but since relink and dynamic instruction size it is ok.
+    # in measures (of 32)
+    if @position != nil and ((@position - pos).abs > 32)
+      raise "position set again #{pos}!=#{@position} for #{self}"
+    end
+    @position = pos
+  end
+end