     end
   end
 
+  % Returns true if integer
   def integer?
     Erlang.is_integer self
   end
 
+  % Returns true if zero
   def zero?
     self == 0
   end
 
+  % Returns true if not zero
   def nonzero?
     !zero?
   end

    end
  end

  def ceil
    case self
    match x when x < 0 then x.truncate

    round
  end

  % Returns the largest Integer less than or equal to self.
  def floor
    case self
    match x when x < 0 then (x - 1).truncate
