For example, the regex [0-9] matches the strings 9 as well as a9b, but the regex ^[0-9]$ only matches 9. By putting ^ at the beginning of your regex and $ at the end, you ensure that no other characters are allowed before or after your regex. 路 0. 0. 0. 0 means that any ip either from a local system or from anywhere on the internet can access. What is the ipv6 address for localhost and for 0. 0. 0. 0 as i need to block some ad hosts. It is everything else other than what is already specified in routing table. The product of 0 and anything is $0$, and seems like it would be reasonable to assume that $0! 路 as we all know the ipv4 address for localhost is 127. 0. 0. 1 (loopback address). Im perplexed as to why i have to account for this condition in my factorial function (trying to learn haskell). 路 the loopback adapter with ip address 127. 0. 0. 1 from the perspective of the server process looks just like any other network adapter on the machine, so a server told to listen on 0. 0. 0. 0 will accept connections on that interface too.