IPAddr#to_s

# File tmp/rubies/ruby-4.0.0/lib/ipaddr.rb, line 205
def to_s
  str = to_string
  return str if ipv4?

  str.gsub!(/\b0{1,3}([\da-f]+)\b/i, '\1')
  loop do
    break if str.sub!(/\A0:0:0:0:0:0:0:0\z/, '::')
    break if str.sub!(/\b0:0:0:0:0:0:0\b/, ':')
    break if str.sub!(/\b0:0:0:0:0:0\b/, ':')
    break if str.sub!(/\b0:0:0:0:0\b/, ':')
    break if str.sub!(/\b0:0:0:0\b/, ':')
    break if str.sub!(/\b0:0:0\b/, ':')
    break if str.sub!(/\b0:0\b/, ':')
    break
  end
  str.sub!(/:{3,}/, '::')

  if /\A::(ffff:)?([\da-f]{1,4}):([\da-f]{1,4})\z/i =~ str
    str = sprintf('::%s%d.%d.%d.%d', $1, $2.hex / 256, $2.hex % 256, $3.hex / 256, $3.hex % 256)
  end

  str
end