def **(other)
      if other.is_a?(Numeric)
        self.class.new(terms.map { |t| t ** other })
      else
        fail TypeError, "Can't raise #{self} to #{other}."
      end
    end
def **(other)
      if other.is_a?(Numeric)
        self.class.new(terms.map { |t| t ** other })
      else
        fail TypeError, "Can't raise #{self} to #{other}."
      end
    end
Raise this unit to a numeric power.
 @param other [Numeric]
 @return [Unitwise::Unit]
 @api public