@c3580d6f thank you!! 

 @3c02b10d aw thank you so much! love to see it 

 @novalis that makes sense thanks -- thinking about it in terms of backtracking seems much more realistic 

 @novalis (when I say "maintaining many parallel possibilites at a time", I'm thinking of this "Implementation: Simulating the NFA" section from https://swtch.com/~rsc/regexp/regexp1.html where he simulates an NFA using an array of states) 

 @novalis 

also I have a pretty clear model of how to "be the computer" for a python program, but for a regex it's harder because actually to match an NFA you have to maintain multiple possibilities in your head at the same time or something? Maintaining 3 parallel possibilities for where in the state machine we could be actually doesn't feel that easy. 

running a DFA computer in your head is pretty easy but I don't think anyone is really converting a regex to a DFA in their head 

 @novalis yeah I have some of the same thoughts since my thoughts about regexes were also formed in theory of computation class

some things I find weird:

- "a regex defines a regular language" doesn't exactly map to regexes in practice (the '?' feels a little slippery to me, and in fact I get a little confused about ?s in my regexes)
- the thing where matching regexes with backreferences is NP-hard (I never use backreferences because they confuse me, but is it bad to use backreferences?) 

 @aa211d11 not yet! i haven't really figured out the right approach to regular expressions, I'm not sure what the hard part is about it yet! 

 @b2f27659 i was surprised by all the replies about firewalls because somehow I forgot that people use iptables to configure firewalls :) (I've mostly used it for NAT and weird container stuff) 

 @04ddd5c0 interesting thanks! do you have any idea what makes vim hard to get into? (ok if not) 

 @72f1dbb9 godspeed