 
       asNode: -> new T.Node2 @a, @b
 
-      norm: -> norm(@a).plus(norm(@b))
+      measure: -> norm @a, @b
 
     @Digit3 = class
       constructor: -> [@a, @b, @c] = arguments

      rest: -> T.Empty
      init: -> T.Empty

      norm: -> norm(@a)

    @Digit2 = class
      constructor: -> [@a, @b] = arguments


      concat: (t) -> t

      measure: -> norm()
    }


