class PrettyBytes

# File lib/pretty_bytes.rb, line 4
def convert(num)
  if num.is_a? Numeric
    neg = num < 0
          units = ['B', 'kB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB']

          if neg
            num = -num
          end

          if num < 1
            return (neg ? '-' : '') + "#{num} B"
          end

          exponent = [(Math.log(num) / Math.log(1000)).floor, units.length - 1].min
          num = "%g" % (num.round(2) / (1000**exponent)).round(2)
          unit = units[exponent]

          return (neg ? '-' : '') + "#{num} " + unit

  else
          return "Expected a number"
        end
end