def thousands x, sep = '_'
      x && x.to_s.reverse!.gsub(/(\d{3})/, "\\1#{sep}").reverse!.sub(/^(\D|\A)#{sep}/, '')
    end
def thousands x, sep = '_'
      x && x.to_s.reverse!.gsub(/(\d{3})/, "\\1#{sep}").reverse!.sub(/^(\D|\A)#{sep}/, '')
    end
Format as ASCII table.