Show HN: Regex Cheatsheet • Hacker News Board

Re: Show HN: Regex Cheatsheet

#21

Post by darau1 » Fri, Jan 31, 2020, 2:27 PM UTC

Nobody pointed it out, but there's also https://regexr.com/

It's how I learned regex years ago, and I still use it today to test/build more complex patterns.

Re: Show HN: Regex Cheatsheet

#22

Post by leibnitz27 » Fri, Jan 31, 2020, 2:33 PM UTC

__tk__ wrote: post #3

I'm loving the graphs which for the first time in years are giving me an idea of what an expression is actually doing. Just because the visualization is kept in a form that is easy to understand with a programming background but can also be translated to the expression itself in a straightforward manner.

I knocked up a silly dynamic regex grapher a while back as a little teaching aid - mildly fun

https://www.benf.org/other/regexview/

Re: Show HN: Regex Cheatsheet

#23

Post by ape4 » Fri, Jan 31, 2020, 2:36 PM UTC

The IPv6 regex is surprisingly complicated.

Re: Show HN: Regex Cheatsheet

#24

Post by dan_hawkins » Fri, Jan 31, 2020, 2:40 PM UTC

Is there a bug? In regexp for IPv4: https://ihateregex.io/expr/ip expression ends with {3} but the diagram states "2 times" in lower right - shouldn't it say "3 times"?

Re: Show HN: Regex Cheatsheet

#25

Post by blauditore » Fri, Jan 31, 2020, 2:41 PM UTC

Would be nice to have a regex for parsing HTML...

grabs popcorn

Re: Show HN: Regex Cheatsheet

#26

Post by jve » Fri, Jan 31, 2020, 2:44 PM UTC

dan_hawkins wrote: post #24

Is there a bug? In regexp for IPv4: https://ihateregex.io/expr/ip expression ends with {3} but the diagram states "2 times" in lower right - shouldn't it say "3 times"?

I think it says "repeat 2" times. So basically you'v already went through the group and then 2 more times.

Because if I specify x{0,3}, i have 2 paths - around x and thru x + at most 2 more times

Re: Show HN: Regex Cheatsheet

#27

Post by geongeorgek » Fri, Jan 31, 2020, 2:48 PM UTC

Amarok wrote: post #19

^[a-z0-9_-]{3,15}$ The username reference doesn't match 16 characters as claimed

I should match. the number 15 there means that repeat x up to 15 times. so 1+15=16.

looks good to me

Re: Show HN: Regex Cheatsheet

#28

Post by geongeorgek » Fri, Jan 31, 2020, 2:49 PM UTC

ape4 wrote: post #23

The IPv6 regex is surprisingly complicated.

Yeah. this is when you start to have 2 problems

Re: Show HN: Regex Cheatsheet

#29

Post by axegon » Fri, Jan 31, 2020, 2:52 PM UTC

This is awesome but.... I don't hate regex. Matter of fact, I love regex.

Re: Show HN: Regex Cheatsheet

#30

Post by anamexis » Fri, Jan 31, 2020, 2:53 PM UTC

skrebbel wrote: post #18

kitd wrote: post #11

This is really cool! 2 points: 1. it fiddled with my back button which is a bit annoying 2. a better email sample is ^[^@]+@[^@]+\.[^@]+$ which removes the 2 ampersands problem.

You'll probably want to add \S to those character classes as well, or it matches "it's an @ sign. not an ampersand."

Escaped or quoted whitespace is allowed in the local part of email addresses.