seperate different Position classes into own files

also tests
and have Position module keep all positions
(singletons should be at module, not class level)

lib/risc/position/object_position.rb

@@ -0,0 +1,36 @@
+module Risc
+  module Position
+    class ObjectPosition
+      attr_reader :at
+
+      def initialize( at )
+        @at = at
+        raise "not int #{self}-#{at}" unless @at.is_a?(Integer)
+      end
+
+      def +(offset)
+        offset = offset.at if offset.is_a?(ObjectPosition)
+        @at + offset
+      end
+
+      def -(offset)
+        offset = offset.at if offset.is_a?(ObjectPosition)
+        @at - offset
+      end
+      def to_s
+        "0x#{@at.to_s(16)}"
+      end
+      # just a callback after creation AND insertion
+      def init(pos)
+      end
+      def reset_to(pos)
+        return false if pos == at
+        if((at - pos).abs > 1000)
+          raise "position set too far off #{pos}!=#{at} for #{object}:#{object.class}"
+        end
+        @at = pos
+        true
+      end
+    end
+  end
+end