# File lib/facets/more/units.rb, line 173
    def to_s
      numerator = ""
      denominator = ""
      @units.each_pair do |u, e|
        (e > 0 ? numerator : denominator) << " #{u.to_s}#{"**#{e.abs}" if e.abs != 1}"
      end
      "#{numerator.lstrip}#{"/" + denominator.lstrip if not denominator.empty?}"
    end