anchor.diff:  }
   
   class ListNode extends Node {
  -
  +  
     static const int LIST_NIL = 0 << Node.KIND_BITS;
     static const int LIST_CONS = 1 << Node.KIND_BITS;
     static const int LIST_MASK = 1 << Node.KIND_BITS;
  
positive.code:     } else if (isFloat()) {
        return that.isFloat() && getFloatValue() == that.getFloatValue();
      }
    }
    
    bool isInt() { return (tag & NUMBER_MASK) == NUMBER_INT; }
  
negative.code: // See the License for the specific language governing permissions and
  // limitations under the License.
  
  /** Represents an ArrowLogo object, primitive or definition.
   *  
   *     WordNode(sv)
   *     NumberNode
   *     - Int(iv)
   *     - Float(fv)
   *     ListNode
   *     - Cons(hd, tl)
   *     - Nil()
   *     Primitive  // see Primitive.dart
   *     Defn(name, arity, body)
   */
  class Node {
    
    static const int KIND_WORD = 0;
    static const int KIND_LIST = 1;
    static const int KIND_NUMBER = 2;
  