# File lib/ipaddress/ipv6.rb, line 555
    def self.groups(str)
      l, r = if str =~ /^(.*)::(.*)$/
               [$1,$2].map {|i| i.split ":"}
             else
               [str.split(":"),[]]
             end
      (l + Array.new(8-l.size-r.size, '0') + r).map {|i| i.hex}
    end