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Regexper – Regular expressions visualizer

510 points by xchip 9y ago

erric 9y ago
Neat! I also suggest: https://regexr.com/ https://regexr.com/
- ChrisGranger 9y ago
  I'm fond of https://regex101.com/ https://regex101.com/ as well.
  - testvox 9y ago
    This site is what finally made me good at regex. I found it painful to learn otherwise.
  - criley2 9y ago
    I'm 100% behind you here. Comparing [1] and [2], there's no competition. [1] https://regexper.com/#%5E(%3F%3A(%3F%3A(%3F%3A0%3F%5B13578%5D%7C1%5B02%5D)(%5C%2F%7C-%7C%5C.)31)%5C1%7C(%3F%3A(%3F%3A0%3F%5B13-9%5D%7C1%5B0-2%5D)(%5C%2F%7C-%7C%5C.)(%3F%3A29%7C30)%5C2))(%3F%3A(%3F%3A1%5B6-9%5D%7C%5B2-9%5D%5Cd)%3F%5Cd%7B2%7D)%24%7C%5E(%3F%3A0%3F2(%5C%2F%7C-%7C%5C.)29%5C3(%3F%3A(%3F%3A(%3F%3A1%5B6-9%5D%7C%5B2-9%5D%5Cd)%3F(%3F%3A0%5B48%5D%7C%5B2468%5D%5B048%5D%7C%5B13579%5D%5B26%5D)%7C(%3F%3A(%3F%3A16%7C%5B2468%5D%5B048%5D%7C%5B3579%5D%5B26%5D)00))))%24%7C%5E(%3F%3A(%3F%3A0%3F%5B1-9%5D)%7C(%3F%3A1%5B0-2%5D))(%5C%2F%7C-%7C%5C.)(%3F%3A0%3F%5B1-9%5D%7C1%5Cd%7C2%5B0-8%5D)%5C4(%3F%3A(%3F%3A1%5B6-9%5D%7C%5B2-9%5D%5Cd)%3F%5Cd%7B2%7D)%24 https://regexper.com/#%5E(%3F%3A(%3F%3A(%3F%3A0%3F%5B13578%5... [2] https://regex101.com/r/LzdGpw/1 https://regex101.com/r/LzdGpw/1 I can use 2, but 1 just looks cool.
  - FridgeSeal 9y ago
    Regex101 is actually awesome. It's what I reach for whenever I've got to do stuff in regex.
  - fergie 9y ago
    Regex101 is the daddy. I really don’t know how it could be improved.
- vanthiathevan 9y ago
  That is cool. https://www.debuggex.com/ https://www.debuggex.com/ has nice visualization.
  - noio 9y ago
    Wow, that is really cool. I actually started typing in random characters and tracing the matches through the graph for the Regex from StackOverflow mentioned earlier. I didn't know what the regex matches, so I played it like a game , trying to reach the finish by typing one character at a time. When I finished, I saw that I had typed "01/31/1691" and then realised that it's a regex for dates.
    - overlordalex 9y ago
      Sounds like you'd love https://regexcrossword.com/ https://regexcrossword.com/
      - BenjiWiebe 9y ago
        +1 for regex crossword. That's a lot of fun.
  - dugluak 9y ago
    That is so fast!
- paradite 9y ago
  I used regexr quite a lot during my daily work. I think regexper more suited for complex structures whereas regexr is better for checking the meaning of simple expressions because of the hover-over function.
  - foobarchu 9y ago
    Agreed. I use regexr daily for building my regex's without having to execute the programs they'll be part of.
- jsilence 9y ago
  emacs also has a visual regexp builder mode (M-x re-builder) that shows the 200 first matches in the current buffer to validate that the regular expression does what you want. But AFAIR there are syntax differences between different regexp flavors and emacs uses the elisp flavor of course.
coinerone 9y ago
My best friend for Regex: http://www.txt2re.com/ http://www.txt2re.com/ With code examples!
gilleain 9y ago
Nice. From this SO answer: https://stackoverflow.com/a/800847/415384 https://stackoverflow.com/a/800847/415384 we get this: https://regexper.com/#%5E(%3F%3A(%3F%3A(%3F%3A0%3F%5B13578%5D%7C1%5B02%5D)(%5C%2F%7C-%7C%5C.)31)%5C1%7C(%3F%3A(%3F%3A0%3F%5B13-9%5D%7C1%5B0-2%5D)(%5C%2F%7C-%7C%5C.)(%3F%3A29%7C30)%5C2))(%3F%3A(%3F%3A1%5B6-9%5D%7C%5B2-9%5D%5Cd)%3F%5Cd%7B2%7D)%24%7C%5E(%3F%3A0%3F2(%5C%2F%7C-%7C%5C.)29%5C3(%3F%3A(%3F%3A(%3F%3A1%5B6-9%5D%7C%5B2-9%5D%5Cd)%3F(%3F%3A0%5B48%5D%7C%5B2468%5D%5B048%5D%7C%5B13579%5D%5B26%5D)%7C(%3F%3A(%3F%3A16%7C%5B2468%5D%5B048%5D%7C%5B3579%5D%5B26%5D)00))))%24%7C%5E(%3F%3A(%3F%3A0%3F%5B1-9%5D)%7C(%3F%3A1%5B0-2%5D))(%5C%2F%7C-%7C%5C.)(%3F%3A0%3F%5B1-9%5D%7C1%5Cd%7C2%5B0-8%5D)%5C4(%3F%3A(%3F%3A1%5B6-9%5D%7C%5B2-9%5D%5Cd)%3F%5Cd%7B2%7D)%24 https://regexper.com/#%5E(%3F%3A(%3F%3A(%3F%3A0%3F%5B13578%5... or from another answer: https://regexper.com/#((1%7C0(00)*01)((11%7C10(00)*01))*%7C(0(00)*1%7C(1%7C0(00)*01)((11%7C10(00)*01))*(0%7C10(00)*1))((1(00)*1%7C(0%7C1(00)*01)((11%7C10(00)*01))*(0%7C10(00)*1)))*(0%7C1(00)*01)((11%7C10(00)*01))*) https://regexper.com/#((1%7C0(00)*01)((11%7C10(00)*01))*%7C(...)
- awhiskeyshot 9y ago
  That last link shows an error.
  - rplnt 9y ago
    Add ')' at the very end (you can see it is not included in the clickable link and it's also what the error says).
    - gilleain 9y ago
      Thanks, fixed!
  - deleted 9y ago
    [deleted]
- jnordwick 9y ago
  Thad first one doesn't seem very good. It seems like there are many places states could be merged. Eg, there are 4 different "^0" states and 3 "^1" states. or am i misreading something?
kenborge 9y ago
Does not look like it supports negative lookbehind https://regexper.com/#(%3F%3C!a)b https://regexper.com/#(%3F%3C!a)b
- barryoneill 9y ago
  I'm sure they'd appreciate a ticket - There's already this which is similar: https://github.com/javallone/regexper-static/issues/26 https://github.com/javallone/regexper-static/issues/26
- onion2k 9y ago
  It does do negative lookahead though - https://regexper.com/#%2F%5Cd%2B(%3F!%5C.)%2F https://regexper.com/#%2F%5Cd%2B(%3F!%5C.)%2F Negative lookbehind only appeared in Chrome in v.62 (https://v8project.blogspot.co.uk/2017/09/v8-release-62.html https://v8project.blogspot.co.uk/2017/09/v8-release-62.html) it's not too surprising that tools haven't caught up yet.
nickcw 9y ago
Here is a regexp to match an IPv4 address - looks quite nice and easy to understand compared to the regexp! In fact the visualisation makes it easy to spot the mistake. https://regexper.com/#'%5Cb((25%5B0-5%5D%7C2%5B0-4%5D%5B0-9%5D%7C%5B01%5D%3F%5B0-9%5D%5B0-9%5D%3F)(%5C.%7C%24))%7B4%7D%5Cb' https://regexper.com/#'%5Cb((25%5B0-5%5D%7C2%5B0-4%5D%5B0-9%... (From https://stackoverflow.com/q/5284147/164234 https://stackoverflow.com/q/5284147/164234 )
- dmayle 9y ago
  The visualization tool shows that the regex is not correct. It allows 000.000.000.000 as an IPv4 address
  - grok2 9y ago
    I created this instead: https://regexper.com/#((%5B0-9%5D%5C.)%7C(%5B1-9%5D%5B0-9%5D%5C.)%7C(1%5B0-9%5D%5B0-9%5D%5C.)%7C(2%5B0-5%5D%5B0-5%5D%5C.))%7B3%7D((%5B0-9%5D)%7C(%5B1-9%5D%5B0-9%5D)%7C(1%5B0-9%5D%5B0-9%5D)%7C(2%5B0-5%5D%5B0-5%5D))(%24) https://regexper.com/#((%5B0-9%5D%5C.)%7C(%5B1-9%5D%5B0-9%5D... The repetition count seems to be displayed off-by-one though.
    - reificator 9y ago
      On mobile so can't (easily) test it, but doesn't this produce a false negative for `246.{snip}`, for example?
      - grok2 9y ago
        Yes, you are right...the following better? https://regexper.com/#((%5B0-9%5D%5C.)%7C(%5B1-9%5D%5B0-9%5D%5C.)%7C(1%5B0-9%5D%5B0-9%5D%5C.)%7C(2%5B0-4%5D%5B0-9%5D%5C.)%7C(25%5B0-5%5D%5C.))%7B3%7D((%5B0-9%5D)%7C(%5B1-9%5D%5B0-9%5D)%7C(1%5B0-9%5D%5B0-9%5D)%7C(2%5B0-4%5D%5B0-9%5D)%7C(25%5B0-5%5D))(%24) https://regexper.com/#((%5B0-9%5D%5C.)%7C(%5B1-9%5D%5B0-9%5D...
    - emj 9y ago
      Does not match: 10.1 -> 10.0.0.1
jdnier 9y ago
Should I expect to have to to escape "/" as "\/"?
- jdnier 9y ago
  Complex regexes do render (must escape "/"). https://regexper.com/#%5B%5E%3C%5D%2B%7C%3C https://regexper.com/#%5B%5E%3C%5D%2B%7C%3C(!(--(%5B%5E-%5D-(%5B%5E-%5D%5B%5E-%5D-)-%3E%3F)%3F%7C%5C%5BCDATA%5C%5B(%5B%5E%5D%5D%5D(%5B%5E%5D%5D%2B%5D)%5D%2B(%5B%5E%5D%3E%5D%5B%5E%5D%5D%5D(%5B%5E%5D%5D%2B%5D)%5D%2B)%3E)%3F%7CDOCTYPE(%5B%20%5Cn%5Ct%5Cr%5D%2B(%5BA-Za-z_%3A%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5BA-Za-z0-9_%3A.-%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5B%20%5Cn%5Ct%5Cr%5D%2B((%5BA-Za-z_%3A%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5BA-Za-z0-9_%3A.-%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)%7C%22%5B%5E%22%5D%22%7C'%5B%5E'%5D'))(%5B%20%5Cn%5Ct%5Cr%5D%2B)%3F(%5C%5B(%3C(!(--%5B%5E-%5D-(%5B%5E-%5D%5B%5E-%5D-)-%3E%7C%5B%5E-%5D(%5B%5E%5D%22'%3E%3C%5D%2B%7C%22%5B%5E%22%5D%22%7C'%5B%5E'%5D')%3E)%7C%5C%3F(%5BA-Za-z_%3A%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5BA-Za-z0-9_%3A.-%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5C%3F%3E%7C%5B%5Cn%5Cr%5Ct%20%5D%5B%5E%3F%5D%5C%3F%2B(%5B%5E%3E%3F%5D%5B%5E%3F%5D%5C%3F%2B)%3E))%7C%25(%5BA-Za-z_%3A%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5BA-Za-z0-9_%3A.-%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)%3B%7C%5B%20%5Cn%5Ct%5Cr%5D%2B)%5D(%5B%20%5Cn%5Ct%5Cr%5D%2B)%3F)%3F%3E%3F)%3F)%3F%7C%5C%3F((%5BA-Za-z_%3A%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5BA-Za-z0-9_%3A.-%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5C%3F%3E%7C%5B%5Cn%5Cr%5Ct%20%5D%5B%5E%3F%5D%5C%3F%2B(%5B%5E%3E%3F%5D%5B%5E%3F%5D%5C%3F%2B)%3E)%3F)%3F%7C%5C%2F((%5BA-Za-z_%3A%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5BA-Za-z0-9_%3A.-%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5B%20%5Cn%5Ct%5Cr%5D%2B)%3F%3E%3F)%3F%7C((%5BA-Za-z_%3A%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5BA-Za-z0-9_%3A.-%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5B%20%5Cn%5Ct%5Cr%5D%2B(%5BA-Za-z_%3A%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5BA-Za-z0-9_%3A.-%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5B%20%5Cn%5Ct%5Cr%5D%2B)%3F%3D(%5B%20%5Cn%5Ct%5Cr%5D%2B)%3F(%22%5B%5E%3C%22%5D%22%7C'%5B%5E%3C'%5D'))*(%5B%20%5Cn%5Ct%5Cr%5D%2B)%3F%5C%2F%3F%3E%3F)%3F) http://www.cs.sfu.ca/~cameron/REX.html http://www.cs.sfu.ca/~cameron/REX.html
  - jdnier 9y ago
    Horizontal scroll would be useful.
avar 9y ago
The Email::Valid Perl distribution ships with a more than 6000 character regex to validate E-Mail addresses. Both goo.gl and bit.ly refused to shorten it, and when I tried to paste the link here HN refused to accept my comment. But on a machine with Email::Valid installed do: perl -MEmail::Valid -wE 'say $Email::Valid::RFC822PAT' And copy the output into the Regexper form. It takes a while to render, but it'll eventually complete.
- gruez 9y ago
  >Both goo.gl and bit.ly refused to shorten it, and when I tried to paste the link here HN refused to accept my comment. github gist?
  - shakna 9y ago
    Try this: https://gist.github.com/shakna-israel/83b84cd8465d131f9686906d15fe60d5 https://gist.github.com/shakna-israel/83b84cd8465d131f968690...
- shakna 9y ago
  Wow. Despite the utterly insane complexity of a regex of that size, it doesn't seem to do an insane amount of branching. Maximum depth of choices seems to be about 4, which is less than a lot of other regex examples I've seen here. That being said... That regex is just noise. Nobody can tackle it all at once or by themselves, unless they specialise in just regex. It's 6599 characters, at least on my system. So at a wild stab, its the equivalent of 4,500 lines of obfuscated code. You can't audit it, you just kinda have to trust it, and hope. But with something like regexper, I can at least read it.
  - avar 9y ago
    I can't remember where, but there's some version of that regex somewhere that uses variables for interpolation in subsequent regexes. Viewed like that it's really not that complex, most of it is repetition of previously used regex sequences, it's only when fully expanded that it becomes so humongous.
antonagestam 9y ago
Isn't this just debuggex.com? That's hacker but not news.
- freehunter 9y ago
  The guidelines say you can post whatever is interesting to hackers, whether it's new/news or not.
kawera 9y ago
Suggestion: put a link to one or two examples to quickly get an idea of what it does.
- rplnt 9y ago
  And base64 share urls.
ythn 9y ago
This is very well made. I don't know what I was expecting, but this really impressed me.
sevensor 9y ago
This is a nifty tool, and to be honest I was unaware that regex visualization was a thing before now. I usually write comments in BNF next to my regex, so that I can make sense of them later. I'm going to keep doing that, but visualization is going to be great for debugging and for figuring out other people's less carefully commented regex.
Raphmedia 9y ago
There's also http://emailregex.com/regex-visual-tester/#(%3F%3A%5Ba-z0-9!%23%24%25%26'*%2B%2F%3D%3F%5E_%60%7B%7C%7D~-%5D%2B(%3F%3A%5C.%5Ba-z0-9!%23%24%25%26'*%2B%2F%3D%3F%5E_%60%7B%7C%7D~-%5D%2B)*%7C%22(%3F%3A%5B%5Cx01-%5Cx08%5Cx0b%5Cx0c%5Cx0e-%5Cx1f%5Cx21%5Cx23-%5Cx5b%5Cx5d-%5Cx7f%5D%7C%5C%5C%5B%5Cx01-%5Cx09%5Cx0b%5Cx0c%5Cx0e-%5Cx7f%5D)*%22)%40(%3F%3A(%3F%3A%5Ba-z0-9%5D(%3F%3A%5Ba-z0-9-%5D*%5Ba-z0-9%5D)%3F%5C.)%2B%5Ba-z0-9%5D(%3F%3A%5Ba-z0-9-%5D*%5Ba-z0-9%5D)%3F%7C%5C%5B(%3F%3A(%3F%3A25%5B0-5%5D%7C2%5B0-4%5D%5B0-9%5D%7C%5B01%5D%3F%5B0-9%5D%5B0-9%5D%3F)%5C.)%7B3%7D(%3F%3A25%5B0-5%5D%7C2%5B0-4%5D%5B0-9%5D%7C%5B01%5D%3F%5B0-9%5D%5B0-9%5D%3F%7C%5Ba-z0-9-%5D*%5Ba-z0-9%5D%3A(%3F%3A%5B%5Cx01-%5Cx08%5Cx0b%5Cx0c%5Cx0e-%5Cx1f%5Cx21-%5Cx5a%5Cx53-%5Cx7f%5D%7C%5C%5C%5B%5Cx01-%5Cx09%5Cx0b%5Cx0c%5Cx0e-%5Cx7f%5D)%2B)%5C%5D http://emailregex.com/regex-visual-tester/#(%3F%3A%5Ba-z0-9!...) Edit: Add the missing ) to the url
thrownaway954 9y ago
The could really use a bunch of "try it" links or examples to show what it can do.
dbcurtis 9y ago
I love the graphics. I would like the equivalent for Python and the GNU flex (lexer) RE's. No... wait.... I know what I want! I want a sphinx extension that allows me to include an RE in a Python docstring and have it render as a railroad track graphic in the generated documentation: some_re_string = r'ab[0-9]*z' """:regex: Any string starting whith 'ab', followed by digits, ending with 'z'. """ That should be able to go pick up the documented string and render a railroad track diagram along with the text in the generated documentation.
royal_ts 9y ago
I'd love to have it the other way around. Human speech to RegExp.I find it really hard to write these expression, e. g.: A colleague needed to write a RegExp for a nickname alias for a URL. It had to have only letters and numbers or a specific number. So either name34 na34me or 23 would be valid.
cel1ne 9y ago
After 20 years of software development I‘ve come to adopt a best practise: Whenever I start writing a regular expression, I stop and write a „manual“ domain specific parse function instead. Saved me a LOT of debugging time. Since I can now use kotlin pretty much anywhere (jvm, browser, shellscripts) this is easy because of the superb stdlib („startsWith“, „lastIndexOf“, „substringBeforeLast(...)“) The time saved I invest in Unittests for the parser.
- darethas 9y ago
  Yep. I primarily use Go, so you are often forced down this way because it uses a simpler regex engine. I used to complain but in hindsight I realized it was a blessing in disguise. Particularly in Go's case, it has excellent character set library support, especially unicode, so those really tricky corner cases with unicode characters are non-existent now as well. I will be happy if I never see a regex with a unicode range again.
  - cel1ne 9y ago
    Which IDE do you use?
    - darethas 9y ago
      I just use a text editor with plugins.
- hinkley 9y ago
  I can't shake the feeling that Regexp could be written just as efficiently as a fluent interface with a more human friendly syntax. I've been telling Jr devs bucking for promotion for years to explain what they're doing in plain english, then write code that looks like that. Basically telling them to skip right over the "gee look what a clever fuck I am" stage and write good code instead of creating riddles. The Regexp problem just screams this at me. What am I doing? I'm looking for a line that starts with a capital T, then has some quantity of alphanumeric characters greater than n (if n is not 0, 1, or infinity, this requires extra work in Regex), followed by an equals sign with or without whitespace characters around it. Give me an API that does exactly that, instead of Regex. Something gets lost in translation every time. I think the fact that the origin of Regex is the command line interface is pretty telling. We didn't and we don't have a convenient way to type in imperative code on a command line. So an arcane syntax was created so you could do the whole thing in a quarter line of text. Speaking as someone who has had a Unix shell for 25 years, and routinely works on mini tools for their fellow developers, I don't think we actually type stuff into a shell that often anymore. The difference between documenting a one-liner in a README and just building a shell script that does the same thing is not that big. There's a difference in development effort but building a script can allow you access to a debugger. Personally, I'd be willing to pay that tax any day.
lerie82 9y ago
I love it, I wish there was support for more regex, c#, etc
ken 9y ago
It's always neat to see where one's ideas go! AFAIK, I was the first person to create dynamic railroad diagrams for regular expressions (maybe 12 or 13 years ago). I got the idea from json.org, which I think was Douglas Crockford's brainchild. My initial implementation was strfriend.com (in Lisp: well under 1,000 lines, including views), and I think its main claim to fame was that Jeff Atwood made fun of it on Twitter. (I was truly clueless at promoting myself back then. Not only did I not have a Twitter account, but it didn't occur to me to submit it to HN.) Every so often, I toy around with the idea of making it into a proper local/native application -- maybe someday. In the meantime, my obsession with regular expressions lives on in my current application (see bio) where I parse and rewrite the user's entered regex syntax (ICU) into whatever regex syntax the backend requires. I don't know of any other application that does this, but I predict that in 15 years it'll be commonplace (and I'll still be poor)!
- kyberias 9y ago
  I was taught the algorithms to do this stuff in my Computer Science class over 20 years ago (RE is equivalent to DFA). You weren't the first person to implement regular expression visualizations.
  - skate22 9y ago
    A dynamic visualization on the web 13 years ago? He may have been the first.
    - osteele 9y ago
      It was pretty hard to do viz on the web 13 years ago. In 2006 I made a web tool to turn regular expressions into NFAs and DFAs and animate their states as you typed. It took a lot of code (drawing and animating along beziers, AJAX to a server for graphviz and a regex compilation and minimization package I wrote for this). https://imgur.com/gallery/Yqqoh https://imgur.com/gallery/Yqqoh These days there’s a lot more tooling and components that can snap together to make this kind of thing.
    - dspillett 9y ago
JelteF 9y ago
Looks neat, but after a quick look I think I still like https://www.debuggex.com/ https://www.debuggex.com/ better. Going step by step through the regex for a given string is really a killer feature for me.
- deepsun 9y ago
  Yep, and not having to click "Display" button each time. Also, partially highlighting the text you write is a pretty hard feature to implement, I did it once. Kudos to debuggex.com for working correctly even with browser zoom on.
kmill 9y ago
Back when https://xkcd.com/1930/ https://xkcd.com/1930/ was posted, I made a regular expression to create a generator using a regex sampler (for instance http://dwickern.github.io/regex-sample/ http://dwickern.github.io/regex-sample/ ). I've put the regex at https://gist.github.com/kmill/17c5ef4f99bd9ef7ad799f0b4874484a https://gist.github.com/kmill/17c5ef4f99bd9ef7ad799f0b487448... The amusing thing to me is that this regex visualizer can reproduce the comic.
- Corrado 9y ago
  https://regexper.com/#%5EDid%20you%20know%20that%20(the%20(fall%7Cspring)%20equinox%7Cthe%20(winter%7Csummer)%20(solstice%7COlympics)%7Cthe%20(earliest%7Clatest)%20(sunrise%7Csunset)%7Cdaylight%20savings%3F%20time%7Cleap%20(day%7Cyear)%7CEaster%7Cthe%20(harvest%7Csuper%7Cblood)%20moon%7CToyota%20truck%20month%7Cshark%20week)%20(happens%20(earlier%7Clater%7Cat%20the%20wrong%20time)%20every%20year%7Cdrifts%20out%20of%20sync%20with%20the%20(sun%7Cmoon%7Czodiac%7C(Gregorian%7CMayan%7Clunar%7CiPhone)%20calendar%7Catomic%20clock%20in%20Colorado)%7Cmight%20(not%20happen%7Chappen%20twice)%20this%20year)%20because%20of%20(time%20zone%20legislation%20in%20(Indiana%7CArizona%7CRussia)%7Ca%20decree%20by%20the%20pope%20in%20the%201500s%7C(precession%7Clibration%7Cnutation%7Clibation%7Ceccentricity%7Cobliquity)%20of%20the%20(moon%7Csun%7CEarth's%20axis%7Cequator%7Cprime%20meridian%7C(international%20date%7CMason-Dixon)%20line)%7Cmagnetic%20field%20reversal%7Can%20arbitray%20decision%20by%20(Benjamin%20Franklin%7CIsaac%20Newton%7CFDR))%5C%3F%20Apparently%20(it%20causes%20a%20predictable%20increase%20in%20car%20accidents%7Cthat's%20why%20we%20have%20leap%20seconds%7Cscientists%20are%20really%20worried%7Cit%20was%20even%20more%20extreme%20during%20the%20(bronze%20age%7Cice%20age%7CCretaceous%7C1990s)%7Cthere's%20a%20proposal%20to%20fix%20it%2C%20but%20it%20(will%20never%20happen%7Cactually%20makes%20things%20worse%7Cis%20stalled%20in%20Congress%7Cmight%20be%20unconstitutional)%7Cit's%20getting%20worse%20and%20no%20one%20knows%20why)%5C.%24 https://regexper.com/#%5EDid%20you%20know%20that%20(the%20(f...
jnordwick 9y ago
I would think it would be better to minimize the pseudo dfa to collapse states. Also having each character of an alternation of subset in light blue box then laying them out vertically makes the hard to read. Of the point of this is to make regex more easily understood, you would think you would want to make them compact.
bart42_0 9y ago
^I love it$
sfkamath 9y ago
searched for some javascript regex's to test it with and found the regex chapter from Eloquent javascript https://eloquentjavascript.net/09_regexp.html https://eloquentjavascript.net/09_regexp.html Coincidence that the diagrams seem to be generated by regexper !
shalabajzer 9y ago
has a bug: {2,4} displayed as 1..3 times
- bhrgunatha 9y ago
  I noticed it translates repeats into a form with a required first character/group so 5{2,4} became 55{1,3} - see https://regexper.com/#5%7B2%2C4%7D https://regexper.com/#5%7B2%2C4%7D
tzury 9y ago
Nicely done! I use https://www.debuggex.com/ https://www.debuggex.com/ on a daily basis. If you want to improve your regex skills, Regex Golf is the place to go! https://alf.nu/RegexGolf https://alf.nu/RegexGolf
mdip 9y ago
I'm an rx geek and can often craft what I'm looking to get without a lot of help, but I have used this tool many times before -- it's very slick. It would be nice if it supported something other than JavaScript[0], but hey, it's on the web, it probably makes a lot of sense to be that way (and it's nice that it's all client-side and I don't have to wait for it to ship my regular expression back to a server for processing). Regular expressions are simply awesome and I'm continually surprised at how frequently I run into developers who have next-to-no understanding of them.Case in point, I ran into some code a few months ago that spanned two methods and 20-lines to do something that a 6-character regular expression could have solved (and would have done so more performantly[1]); the best part was that part of what I was responsible for handling was a bug that ended up residing right inside one of those methods. And then there's all of the things related to "dealing with strings" that many regular expression libraries just handle, such as "\d" vs "[0-9]" in a world with unicode strings[3]. It feels cryptic[4] when you encounter it and you're not familiar with the syntax, but to learn the "80% most useful parts", you needn't study much more than content that would fit on a single printed sheet of paper (and to get the last 20%, you'd need, maybe 2, ... 3?) All of that said, there's also the other side of the coin; if ever the saying "If all you have is a hammer, everything looks like a nail" had application, it's with regular expressions. I'm not sure how many times the question "How do I write a regular expression to parse HTML" has to be responded with "don't" before folks quit trying[2]. It tends to be the first thing I reach for when I have a need to process text, even when there are better tools; heck, all of my find/replace dialogues in every application that supports it have the "Regex" box checked by default (and it really throws me off when I hit up "Find" in the browser and need to search for something with a ( or ) in it which I escape due to muscle memory) [0] I have an occasional need for PCRE and .NET style; and I really miss named-groups when I have to do something complex in JavaScript. [1] While it's easy to accidentally end up in hell, ala https://blog.codinghorror.com/regex-performance/ https://blog.codinghorror.com/regex-performance/, poorly written string-search code can be worse when the complexity of the pattern your searching for reaches a certain point, and that's to say nothing of the errors per x lines of code and readability (not that rx is particularly readable under complexity). [2] And hey, I've got a shell script that downloads a few status pages on my server at home that uses awk with regular expressions to extract values from a web page. I wouldn't say it necessarily qualifies as "parsing HTML" since it's really only concerned with looking for a small string which it filters a second time to get the value -- horribly inefficient, but it's worked for 5 years through page changes without requiring adjustment. [3] At least in the C# world, are about twice as slow due to handling digits "correctly" https://stackoverflow.com/questions/16621738/d-is-less-efficient-than-0-9 https://stackoverflow.com/questions/16621738/d-is-less-effic... [4] While it's usually written cryptically, many (most?) implementations support flags to ignore whitespace and support comment features. I've had a few crazy-ugly rx's that I had to use to extract data from a ticketing system's "blob field" to insert into a structured format; were it not for that feature, it would have been impossible to write and support.
teddyh 9y ago
In Emacs: M-x regexp-builder
chatmasta 9y ago
Nicely done. Next step, can you do it in reverse? Would be cool to create the regex in a graphical editor and then generate the actual expression. Feature request: export the visualization to ascii, so I can copy paste it into a comment above the regex in my code.
Kagerjay 9y ago
Here's an example of a regex to validate us phone numbers https://regexper.com/#%2F%5E(1%5Cs%3F)%3F(%5B0-9%5D%7B3%7D%7C%5C(%5B0-9%5D%7B3%7D%5C))%5B%5Cs%7C-%5D%3F%5B0-9%5D%7B3%7D%5B%5Cs%7C-%5D%3F%5B0-9%5D%7B4%7D%24%2Fgm https://regexper.com/#%2F%5E(1%5Cs%3F)%3F(%5B0-9%5D%7B3%7D%7... From https://www.freecodecamp.org/challenges/validate-us-telephone-numbers https://www.freecodecamp.org/challenges/validate-us-telephon... I found these 11 videos most helpful when learning regex from codecourse https://www.youtube.com/watch?v=GVZOJ1rEnUg&index=1&list=PLfdtiltiRHWGRPyPMGuLPWuiWgEI9Kp1w https://www.youtube.com/watch?v=GVZOJ1rEnUg&index=1&list=PLf...

510 points by xchip 9y ago

erric 9y ago

Neat! I also suggest: https://regexr.com/ https://regexr.com/

ChrisGranger 9y ago
I'm fond of https://regex101.com/ https://regex101.com/ as well.
- testvox 9y ago
  This site is what finally made me good at regex. I found it painful to learn otherwise.
- criley2 9y ago
  I'm 100% behind you here. Comparing [1] and [2], there's no competition. [1] https://regexper.com/#%5E(%3F%3A(%3F%3A(%3F%3A0%3F%5B13578%5D%7C1%5B02%5D)(%5C%2F%7C-%7C%5C.)31)%5C1%7C(%3F%3A(%3F%3A0%3F%5B13-9%5D%7C1%5B0-2%5D)(%5C%2F%7C-%7C%5C.)(%3F%3A29%7C30)%5C2))(%3F%3A(%3F%3A1%5B6-9%5D%7C%5B2-9%5D%5Cd)%3F%5Cd%7B2%7D)%24%7C%5E(%3F%3A0%3F2(%5C%2F%7C-%7C%5C.)29%5C3(%3F%3A(%3F%3A(%3F%3A1%5B6-9%5D%7C%5B2-9%5D%5Cd)%3F(%3F%3A0%5B48%5D%7C%5B2468%5D%5B048%5D%7C%5B13579%5D%5B26%5D)%7C(%3F%3A(%3F%3A16%7C%5B2468%5D%5B048%5D%7C%5B3579%5D%5B26%5D)00))))%24%7C%5E(%3F%3A(%3F%3A0%3F%5B1-9%5D)%7C(%3F%3A1%5B0-2%5D))(%5C%2F%7C-%7C%5C.)(%3F%3A0%3F%5B1-9%5D%7C1%5Cd%7C2%5B0-8%5D)%5C4(%3F%3A(%3F%3A1%5B6-9%5D%7C%5B2-9%5D%5Cd)%3F%5Cd%7B2%7D)%24 https://regexper.com/#%5E(%3F%3A(%3F%3A(%3F%3A0%3F%5B13578%5... [2] https://regex101.com/r/LzdGpw/1 https://regex101.com/r/LzdGpw/1 I can use 2, but 1 just looks cool.
- FridgeSeal 9y ago
  Regex101 is actually awesome. It's what I reach for whenever I've got to do stuff in regex.
- fergie 9y ago
  Regex101 is the daddy. I really don’t know how it could be improved.
vanthiathevan 9y ago
That is cool. https://www.debuggex.com/ https://www.debuggex.com/ has nice visualization.
- noio 9y ago
  Wow, that is really cool. I actually started typing in random characters and tracing the matches through the graph for the Regex from StackOverflow mentioned earlier. I didn't know what the regex matches, so I played it like a game , trying to reach the finish by typing one character at a time. When I finished, I saw that I had typed "01/31/1691" and then realised that it's a regex for dates.
  - overlordalex 9y ago
    Sounds like you'd love https://regexcrossword.com/ https://regexcrossword.com/
    - BenjiWiebe 9y ago
      +1 for regex crossword. That's a lot of fun.
- dugluak 9y ago
  That is so fast!
paradite 9y ago
I used regexr quite a lot during my daily work. I think regexper more suited for complex structures whereas regexr is better for checking the meaning of simple expressions because of the hover-over function.
- foobarchu 9y ago
  Agreed. I use regexr daily for building my regex's without having to execute the programs they'll be part of.
jsilence 9y ago
emacs also has a visual regexp builder mode (M-x re-builder) that shows the 200 first matches in the current buffer to validate that the regular expression does what you want. But AFAIR there are syntax differences between different regexp flavors and emacs uses the elisp flavor of course.

coinerone 9y ago

My best friend for Regex: http://www.txt2re.com/ http://www.txt2re.com/ With code examples!

gilleain 9y ago

Nice. From this SO answer: https://stackoverflow.com/a/800847/415384 https://stackoverflow.com/a/800847/415384 we get this: https://regexper.com/#%5E(%3F%3A(%3F%3A(%3F%3A0%3F%5B13578%5D%7C1%5B02%5D)(%5C%2F%7C-%7C%5C.)31)%5C1%7C(%3F%3A(%3F%3A0%3F%5B13-9%5D%7C1%5B0-2%5D)(%5C%2F%7C-%7C%5C.)(%3F%3A29%7C30)%5C2))(%3F%3A(%3F%3A1%5B6-9%5D%7C%5B2-9%5D%5Cd)%3F%5Cd%7B2%7D)%24%7C%5E(%3F%3A0%3F2(%5C%2F%7C-%7C%5C.)29%5C3(%3F%3A(%3F%3A(%3F%3A1%5B6-9%5D%7C%5B2-9%5D%5Cd)%3F(%3F%3A0%5B48%5D%7C%5B2468%5D%5B048%5D%7C%5B13579%5D%5B26%5D)%7C(%3F%3A(%3F%3A16%7C%5B2468%5D%5B048%5D%7C%5B3579%5D%5B26%5D)00))))%24%7C%5E(%3F%3A(%3F%3A0%3F%5B1-9%5D)%7C(%3F%3A1%5B0-2%5D))(%5C%2F%7C-%7C%5C.)(%3F%3A0%3F%5B1-9%5D%7C1%5Cd%7C2%5B0-8%5D)%5C4(%3F%3A(%3F%3A1%5B6-9%5D%7C%5B2-9%5D%5Cd)%3F%5Cd%7B2%7D)%24 https://regexper.com/#%5E(%3F%3A(%3F%3A(%3F%3A0%3F%5B13578%5... or from another answer: https://regexper.com/#((1%7C0(00)*01)((11%7C10(00)*01))*%7C(0(00)*1%7C(1%7C0(00)*01)((11%7C10(00)*01))*(0%7C10(00)*1))((1(00)*1%7C(0%7C1(00)*01)((11%7C10(00)*01))*(0%7C10(00)*1)))*(0%7C1(00)*01)((11%7C10(00)*01))*) https://regexper.com/#((1%7C0(00)*01)((11%7C10(00)*01))*%7C(...)

awhiskeyshot 9y ago
That last link shows an error.
- rplnt 9y ago
  Add ')' at the very end (you can see it is not included in the clickable link and it's also what the error says).
  - gilleain 9y ago
    Thanks, fixed!
- deleted 9y ago
  [deleted]
jnordwick 9y ago
Thad first one doesn't seem very good. It seems like there are many places states could be merged. Eg, there are 4 different "^0" states and 3 "^1" states. or am i misreading something?

kenborge 9y ago

Does not look like it supports negative lookbehind https://regexper.com/#(%3F%3C!a)b https://regexper.com/#(%3F%3C!a)b

barryoneill 9y ago
I'm sure they'd appreciate a ticket - There's already this which is similar: https://github.com/javallone/regexper-static/issues/26 https://github.com/javallone/regexper-static/issues/26
onion2k 9y ago
It does do negative lookahead though - https://regexper.com/#%2F%5Cd%2B(%3F!%5C.)%2F https://regexper.com/#%2F%5Cd%2B(%3F!%5C.)%2F Negative lookbehind only appeared in Chrome in v.62 (https://v8project.blogspot.co.uk/2017/09/v8-release-62.html https://v8project.blogspot.co.uk/2017/09/v8-release-62.html) it's not too surprising that tools haven't caught up yet.

nickcw 9y ago

Here is a regexp to match an IPv4 address - looks quite nice and easy to understand compared to the regexp! In fact the visualisation makes it easy to spot the mistake. https://regexper.com/#'%5Cb((25%5B0-5%5D%7C2%5B0-4%5D%5B0-9%5D%7C%5B01%5D%3F%5B0-9%5D%5B0-9%5D%3F)(%5C.%7C%24))%7B4%7D%5Cb' https://regexper.com/#'%5Cb((25%5B0-5%5D%7C2%5B0-4%5D%5B0-9%... (From https://stackoverflow.com/q/5284147/164234 https://stackoverflow.com/q/5284147/164234 )

dmayle 9y ago
The visualization tool shows that the regex is not correct. It allows 000.000.000.000 as an IPv4 address
- grok2 9y ago
  I created this instead: https://regexper.com/#((%5B0-9%5D%5C.)%7C(%5B1-9%5D%5B0-9%5D%5C.)%7C(1%5B0-9%5D%5B0-9%5D%5C.)%7C(2%5B0-5%5D%5B0-5%5D%5C.))%7B3%7D((%5B0-9%5D)%7C(%5B1-9%5D%5B0-9%5D)%7C(1%5B0-9%5D%5B0-9%5D)%7C(2%5B0-5%5D%5B0-5%5D))(%24) https://regexper.com/#((%5B0-9%5D%5C.)%7C(%5B1-9%5D%5B0-9%5D... The repetition count seems to be displayed off-by-one though.
  - reificator 9y ago
    On mobile so can't (easily) test it, but doesn't this produce a false negative for `246.{snip}`, for example?
    - grok2 9y ago
      Yes, you are right...the following better? https://regexper.com/#((%5B0-9%5D%5C.)%7C(%5B1-9%5D%5B0-9%5D%5C.)%7C(1%5B0-9%5D%5B0-9%5D%5C.)%7C(2%5B0-4%5D%5B0-9%5D%5C.)%7C(25%5B0-5%5D%5C.))%7B3%7D((%5B0-9%5D)%7C(%5B1-9%5D%5B0-9%5D)%7C(1%5B0-9%5D%5B0-9%5D)%7C(2%5B0-4%5D%5B0-9%5D)%7C(25%5B0-5%5D))(%24) https://regexper.com/#((%5B0-9%5D%5C.)%7C(%5B1-9%5D%5B0-9%5D...
  - emj 9y ago
    Does not match: 10.1 -> 10.0.0.1

jdnier 9y ago

Should I expect to have to to escape "/" as "\/"?

jdnier 9y ago
Complex regexes do render (must escape "/"). https://regexper.com/#%5B%5E%3C%5D%2B%7C%3C https://regexper.com/#%5B%5E%3C%5D%2B%7C%3C(!(--(%5B%5E-%5D-(%5B%5E-%5D%5B%5E-%5D-)-%3E%3F)%3F%7C%5C%5BCDATA%5C%5B(%5B%5E%5D%5D%5D(%5B%5E%5D%5D%2B%5D)%5D%2B(%5B%5E%5D%3E%5D%5B%5E%5D%5D%5D(%5B%5E%5D%5D%2B%5D)%5D%2B)%3E)%3F%7CDOCTYPE(%5B%20%5Cn%5Ct%5Cr%5D%2B(%5BA-Za-z_%3A%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5BA-Za-z0-9_%3A.-%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5B%20%5Cn%5Ct%5Cr%5D%2B((%5BA-Za-z_%3A%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5BA-Za-z0-9_%3A.-%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)%7C%22%5B%5E%22%5D%22%7C'%5B%5E'%5D'))(%5B%20%5Cn%5Ct%5Cr%5D%2B)%3F(%5C%5B(%3C(!(--%5B%5E-%5D-(%5B%5E-%5D%5B%5E-%5D-)-%3E%7C%5B%5E-%5D(%5B%5E%5D%22'%3E%3C%5D%2B%7C%22%5B%5E%22%5D%22%7C'%5B%5E'%5D')%3E)%7C%5C%3F(%5BA-Za-z_%3A%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5BA-Za-z0-9_%3A.-%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5C%3F%3E%7C%5B%5Cn%5Cr%5Ct%20%5D%5B%5E%3F%5D%5C%3F%2B(%5B%5E%3E%3F%5D%5B%5E%3F%5D%5C%3F%2B)%3E))%7C%25(%5BA-Za-z_%3A%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5BA-Za-z0-9_%3A.-%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)%3B%7C%5B%20%5Cn%5Ct%5Cr%5D%2B)%5D(%5B%20%5Cn%5Ct%5Cr%5D%2B)%3F)%3F%3E%3F)%3F)%3F%7C%5C%3F((%5BA-Za-z_%3A%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5BA-Za-z0-9_%3A.-%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5C%3F%3E%7C%5B%5Cn%5Cr%5Ct%20%5D%5B%5E%3F%5D%5C%3F%2B(%5B%5E%3E%3F%5D%5B%5E%3F%5D%5C%3F%2B)%3E)%3F)%3F%7C%5C%2F((%5BA-Za-z_%3A%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5BA-Za-z0-9_%3A.-%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5B%20%5Cn%5Ct%5Cr%5D%2B)%3F%3E%3F)%3F%7C((%5BA-Za-z_%3A%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5BA-Za-z0-9_%3A.-%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5B%20%5Cn%5Ct%5Cr%5D%2B(%5BA-Za-z_%3A%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5BA-Za-z0-9_%3A.-%5D%7C%5B%5E%5Cx00-%5Cx7F%5D)(%5B%20%5Cn%5Ct%5Cr%5D%2B)%3F%3D(%5B%20%5Cn%5Ct%5Cr%5D%2B)%3F(%22%5B%5E%3C%22%5D%22%7C'%5B%5E%3C'%5D'))*(%5B%20%5Cn%5Ct%5Cr%5D%2B)%3F%5C%2F%3F%3E%3F)%3F) http://www.cs.sfu.ca/~cameron/REX.html http://www.cs.sfu.ca/~cameron/REX.html
- jdnier 9y ago
  Horizontal scroll would be useful.

avar 9y ago

The Email::Valid Perl distribution ships with a more than 6000 character regex to validate E-Mail addresses. Both goo.gl and bit.ly refused to shorten it, and when I tried to paste the link here HN refused to accept my comment. But on a machine with Email::Valid installed do: perl -MEmail::Valid -wE 'say $Email::Valid::RFC822PAT' And copy the output into the Regexper form. It takes a while to render, but it'll eventually complete.

gruez 9y ago
>Both goo.gl and bit.ly refused to shorten it, and when I tried to paste the link here HN refused to accept my comment. github gist?
- shakna 9y ago
  Try this: https://gist.github.com/shakna-israel/83b84cd8465d131f9686906d15fe60d5 https://gist.github.com/shakna-israel/83b84cd8465d131f968690...
shakna 9y ago
Wow. Despite the utterly insane complexity of a regex of that size, it doesn't seem to do an insane amount of branching. Maximum depth of choices seems to be about 4, which is less than a lot of other regex examples I've seen here. That being said... That regex is just noise. Nobody can tackle it all at once or by themselves, unless they specialise in just regex. It's 6599 characters, at least on my system. So at a wild stab, its the equivalent of 4,500 lines of obfuscated code. You can't audit it, you just kinda have to trust it, and hope. But with something like regexper, I can at least read it.
- avar 9y ago
  I can't remember where, but there's some version of that regex somewhere that uses variables for interpolation in subsequent regexes. Viewed like that it's really not that complex, most of it is repetition of previously used regex sequences, it's only when fully expanded that it becomes so humongous.

antonagestam 9y ago

Isn't this just debuggex.com? That's hacker but not news.

freehunter 9y ago
The guidelines say you can post whatever is interesting to hackers, whether it's new/news or not.

kawera 9y ago

Suggestion: put a link to one or two examples to quickly get an idea of what it does.

rplnt 9y ago
And base64 share urls.

ythn 9y ago

This is very well made. I don't know what I was expecting, but this really impressed me.

sevensor 9y ago

This is a nifty tool, and to be honest I was unaware that regex visualization was a thing before now. I usually write comments in BNF next to my regex, so that I can make sense of them later. I'm going to keep doing that, but visualization is going to be great for debugging and for figuring out other people's less carefully commented regex.

Raphmedia 9y ago

There's also http://emailregex.com/regex-visual-tester/#(%3F%3A%5Ba-z0-9!%23%24%25%26'*%2B%2F%3D%3F%5E_%60%7B%7C%7D~-%5D%2B(%3F%3A%5C.%5Ba-z0-9!%23%24%25%26'*%2B%2F%3D%3F%5E_%60%7B%7C%7D~-%5D%2B)*%7C%22(%3F%3A%5B%5Cx01-%5Cx08%5Cx0b%5Cx0c%5Cx0e-%5Cx1f%5Cx21%5Cx23-%5Cx5b%5Cx5d-%5Cx7f%5D%7C%5C%5C%5B%5Cx01-%5Cx09%5Cx0b%5Cx0c%5Cx0e-%5Cx7f%5D)*%22)%40(%3F%3A(%3F%3A%5Ba-z0-9%5D(%3F%3A%5Ba-z0-9-%5D*%5Ba-z0-9%5D)%3F%5C.)%2B%5Ba-z0-9%5D(%3F%3A%5Ba-z0-9-%5D*%5Ba-z0-9%5D)%3F%7C%5C%5B(%3F%3A(%3F%3A25%5B0-5%5D%7C2%5B0-4%5D%5B0-9%5D%7C%5B01%5D%3F%5B0-9%5D%5B0-9%5D%3F)%5C.)%7B3%7D(%3F%3A25%5B0-5%5D%7C2%5B0-4%5D%5B0-9%5D%7C%5B01%5D%3F%5B0-9%5D%5B0-9%5D%3F%7C%5Ba-z0-9-%5D*%5Ba-z0-9%5D%3A(%3F%3A%5B%5Cx01-%5Cx08%5Cx0b%5Cx0c%5Cx0e-%5Cx1f%5Cx21-%5Cx5a%5Cx53-%5Cx7f%5D%7C%5C%5C%5B%5Cx01-%5Cx09%5Cx0b%5Cx0c%5Cx0e-%5Cx7f%5D)%2B)%5C%5D http://emailregex.com/regex-visual-tester/#(%3F%3A%5Ba-z0-9!...) Edit: Add the missing ) to the url

thrownaway954 9y ago

The could really use a bunch of "try it" links or examples to show what it can do.

dbcurtis 9y ago

I love the graphics. I would like the equivalent for Python and the GNU flex (lexer) RE's. No... wait.... I know what I want! I want a sphinx extension that allows me to include an RE in a Python docstring and have it render as a railroad track graphic in the generated documentation: some_re_string = r'ab[0-9]*z' """:regex: Any string starting whith 'ab', followed by digits, ending with 'z'. """ That should be able to go pick up the documented string and render a railroad track diagram along with the text in the generated documentation.

royal_ts 9y ago

I'd love to have it the other way around. Human speech to RegExp.I find it really hard to write these expression, e. g.: A colleague needed to write a RegExp for a nickname alias for a URL. It had to have only letters and numbers or a specific number. So either name34 na34me or 23 would be valid.

cel1ne 9y ago

After 20 years of software development I‘ve come to adopt a best practise: Whenever I start writing a regular expression, I stop and write a „manual“ domain specific parse function instead. Saved me a LOT of debugging time. Since I can now use kotlin pretty much anywhere (jvm, browser, shellscripts) this is easy because of the superb stdlib („startsWith“, „lastIndexOf“, „substringBeforeLast(...)“) The time saved I invest in Unittests for the parser.

darethas 9y ago
Yep. I primarily use Go, so you are often forced down this way because it uses a simpler regex engine. I used to complain but in hindsight I realized it was a blessing in disguise. Particularly in Go's case, it has excellent character set library support, especially unicode, so those really tricky corner cases with unicode characters are non-existent now as well. I will be happy if I never see a regex with a unicode range again.
- cel1ne 9y ago
  Which IDE do you use?
  - darethas 9y ago
    I just use a text editor with plugins.
hinkley 9y ago
I can't shake the feeling that Regexp could be written just as efficiently as a fluent interface with a more human friendly syntax. I've been telling Jr devs bucking for promotion for years to explain what they're doing in plain english, then write code that looks like that. Basically telling them to skip right over the "gee look what a clever fuck I am" stage and write good code instead of creating riddles. The Regexp problem just screams this at me. What am I doing? I'm looking for a line that starts with a capital T, then has some quantity of alphanumeric characters greater than n (if n is not 0, 1, or infinity, this requires extra work in Regex), followed by an equals sign with or without whitespace characters around it. Give me an API that does exactly that, instead of Regex. Something gets lost in translation every time. I think the fact that the origin of Regex is the command line interface is pretty telling. We didn't and we don't have a convenient way to type in imperative code on a command line. So an arcane syntax was created so you could do the whole thing in a quarter line of text. Speaking as someone who has had a Unix shell for 25 years, and routinely works on mini tools for their fellow developers, I don't think we actually type stuff into a shell that often anymore. The difference between documenting a one-liner in a README and just building a shell script that does the same thing is not that big. There's a difference in development effort but building a script can allow you access to a debugger. Personally, I'd be willing to pay that tax any day.

lerie82 9y ago

I love it, I wish there was support for more regex, c#, etc

ken 9y ago

It's always neat to see where one's ideas go! AFAIK, I was the first person to create dynamic railroad diagrams for regular expressions (maybe 12 or 13 years ago). I got the idea from json.org, which I think was Douglas Crockford's brainchild. My initial implementation was strfriend.com (in Lisp: well under 1,000 lines, including views), and I think its main claim to fame was that Jeff Atwood made fun of it on Twitter. (I was truly clueless at promoting myself back then. Not only did I not have a Twitter account, but it didn't occur to me to submit it to HN.) Every so often, I toy around with the idea of making it into a proper local/native application -- maybe someday. In the meantime, my obsession with regular expressions lives on in my current application (see bio) where I parse and rewrite the user's entered regex syntax (ICU) into whatever regex syntax the backend requires. I don't know of any other application that does this, but I predict that in 15 years it'll be commonplace (and I'll still be poor)!

kyberias 9y ago
I was taught the algorithms to do this stuff in my Computer Science class over 20 years ago (RE is equivalent to DFA). You weren't the first person to implement regular expression visualizations.
- skate22 9y ago
  A dynamic visualization on the web 13 years ago? He may have been the first.
  - osteele 9y ago
    It was pretty hard to do viz on the web 13 years ago. In 2006 I made a web tool to turn regular expressions into NFAs and DFAs and animate their states as you typed. It took a lot of code (drawing and animating along beziers, AJAX to a server for graphviz and a regex compilation and minimization package I wrote for this). https://imgur.com/gallery/Yqqoh https://imgur.com/gallery/Yqqoh These days there’s a lot more tooling and components that can snap together to make this kind of thing.
  - dspillett 9y ago

JelteF 9y ago

Looks neat, but after a quick look I think I still like https://www.debuggex.com/ https://www.debuggex.com/ better. Going step by step through the regex for a given string is really a killer feature for me.

deepsun 9y ago
Yep, and not having to click "Display" button each time. Also, partially highlighting the text you write is a pretty hard feature to implement, I did it once. Kudos to debuggex.com for working correctly even with browser zoom on.

kmill 9y ago

Back when https://xkcd.com/1930/ https://xkcd.com/1930/ was posted, I made a regular expression to create a generator using a regex sampler (for instance http://dwickern.github.io/regex-sample/ http://dwickern.github.io/regex-sample/ ). I've put the regex at https://gist.github.com/kmill/17c5ef4f99bd9ef7ad799f0b4874484a https://gist.github.com/kmill/17c5ef4f99bd9ef7ad799f0b487448... The amusing thing to me is that this regex visualizer can reproduce the comic.

Corrado 9y ago
https://regexper.com/#%5EDid%20you%20know%20that%20(the%20(fall%7Cspring)%20equinox%7Cthe%20(winter%7Csummer)%20(solstice%7COlympics)%7Cthe%20(earliest%7Clatest)%20(sunrise%7Csunset)%7Cdaylight%20savings%3F%20time%7Cleap%20(day%7Cyear)%7CEaster%7Cthe%20(harvest%7Csuper%7Cblood)%20moon%7CToyota%20truck%20month%7Cshark%20week)%20(happens%20(earlier%7Clater%7Cat%20the%20wrong%20time)%20every%20year%7Cdrifts%20out%20of%20sync%20with%20the%20(sun%7Cmoon%7Czodiac%7C(Gregorian%7CMayan%7Clunar%7CiPhone)%20calendar%7Catomic%20clock%20in%20Colorado)%7Cmight%20(not%20happen%7Chappen%20twice)%20this%20year)%20because%20of%20(time%20zone%20legislation%20in%20(Indiana%7CArizona%7CRussia)%7Ca%20decree%20by%20the%20pope%20in%20the%201500s%7C(precession%7Clibration%7Cnutation%7Clibation%7Ceccentricity%7Cobliquity)%20of%20the%20(moon%7Csun%7CEarth's%20axis%7Cequator%7Cprime%20meridian%7C(international%20date%7CMason-Dixon)%20line)%7Cmagnetic%20field%20reversal%7Can%20arbitray%20decision%20by%20(Benjamin%20Franklin%7CIsaac%20Newton%7CFDR))%5C%3F%20Apparently%20(it%20causes%20a%20predictable%20increase%20in%20car%20accidents%7Cthat's%20why%20we%20have%20leap%20seconds%7Cscientists%20are%20really%20worried%7Cit%20was%20even%20more%20extreme%20during%20the%20(bronze%20age%7Cice%20age%7CCretaceous%7C1990s)%7Cthere's%20a%20proposal%20to%20fix%20it%2C%20but%20it%20(will%20never%20happen%7Cactually%20makes%20things%20worse%7Cis%20stalled%20in%20Congress%7Cmight%20be%20unconstitutional)%7Cit's%20getting%20worse%20and%20no%20one%20knows%20why)%5C.%24 https://regexper.com/#%5EDid%20you%20know%20that%20(the%20(f...

jnordwick 9y ago

I would think it would be better to minimize the pseudo dfa to collapse states. Also having each character of an alternation of subset in light blue box then laying them out vertically makes the hard to read. Of the point of this is to make regex more easily understood, you would think you would want to make them compact.

bart42_0 9y ago

^I love it$

sfkamath 9y ago

searched for some javascript regex's to test it with and found the regex chapter from Eloquent javascript https://eloquentjavascript.net/09_regexp.html https://eloquentjavascript.net/09_regexp.html Coincidence that the diagrams seem to be generated by regexper !

shalabajzer 9y ago

has a bug: {2,4} displayed as 1..3 times

bhrgunatha 9y ago
I noticed it translates repeats into a form with a required first character/group so 5{2,4} became 55{1,3} - see https://regexper.com/#5%7B2%2C4%7D https://regexper.com/#5%7B2%2C4%7D

tzury 9y ago

Nicely done! I use https://www.debuggex.com/ https://www.debuggex.com/ on a daily basis. If you want to improve your regex skills, Regex Golf is the place to go! https://alf.nu/RegexGolf https://alf.nu/RegexGolf

mdip 9y ago

I'm an rx geek and can often craft what I'm looking to get without a lot of help, but I have used this tool many times before -- it's very slick. It would be nice if it supported something other than JavaScript[0], but hey, it's on the web, it probably makes a lot of sense to be that way (and it's nice that it's all client-side and I don't have to wait for it to ship my regular expression back to a server for processing). Regular expressions are simply awesome and I'm continually surprised at how frequently I run into developers who have next-to-no understanding of them.Case in point, I ran into some code a few months ago that spanned two methods and 20-lines to do something that a 6-character regular expression could have solved (and would have done so more performantly[1]); the best part was that part of what I was responsible for handling was a bug that ended up residing right inside one of those methods. And then there's all of the things related to "dealing with strings" that many regular expression libraries just handle, such as "\d" vs "[0-9]" in a world with unicode strings[3]. It feels cryptic[4] when you encounter it and you're not familiar with the syntax, but to learn the "80% most useful parts", you needn't study much more than content that would fit on a single printed sheet of paper (and to get the last 20%, you'd need, maybe 2, ... 3?) All of that said, there's also the other side of the coin; if ever the saying "If all you have is a hammer, everything looks like a nail" had application, it's with regular expressions. I'm not sure how many times the question "How do I write a regular expression to parse HTML" has to be responded with "don't" before folks quit trying[2]. It tends to be the first thing I reach for when I have a need to process text, even when there are better tools; heck, all of my find/replace dialogues in every application that supports it have the "Regex" box checked by default (and it really throws me off when I hit up "Find" in the browser and need to search for something with a ( or ) in it which I escape due to muscle memory) [0] I have an occasional need for PCRE and .NET style; and I really miss named-groups when I have to do something complex in JavaScript. [1] While it's easy to accidentally end up in hell, ala https://blog.codinghorror.com/regex-performance/ https://blog.codinghorror.com/regex-performance/, poorly written string-search code can be worse when the complexity of the pattern your searching for reaches a certain point, and that's to say nothing of the errors per x lines of code and readability (not that rx is particularly readable under complexity). [2] And hey, I've got a shell script that downloads a few status pages on my server at home that uses awk with regular expressions to extract values from a web page. I wouldn't say it necessarily qualifies as "parsing HTML" since it's really only concerned with looking for a small string which it filters a second time to get the value -- horribly inefficient, but it's worked for 5 years through page changes without requiring adjustment. [3] At least in the C# world, are about twice as slow due to handling digits "correctly" https://stackoverflow.com/questions/16621738/d-is-less-efficient-than-0-9 https://stackoverflow.com/questions/16621738/d-is-less-effic... [4] While it's usually written cryptically, many (most?) implementations support flags to ignore whitespace and support comment features. I've had a few crazy-ugly rx's that I had to use to extract data from a ticketing system's "blob field" to insert into a structured format; were it not for that feature, it would have been impossible to write and support.

teddyh 9y ago

In Emacs: M-x regexp-builder

chatmasta 9y ago

Nicely done. Next step, can you do it in reverse? Would be cool to create the regex in a graphical editor and then generate the actual expression. Feature request: export the visualization to ascii, so I can copy paste it into a comment above the regex in my code.

Kagerjay 9y ago

Here's an example of a regex to validate us phone numbers https://regexper.com/#%2F%5E(1%5Cs%3F)%3F(%5B0-9%5D%7B3%7D%7C%5C(%5B0-9%5D%7B3%7D%5C))%5B%5Cs%7C-%5D%3F%5B0-9%5D%7B3%7D%5B%5Cs%7C-%5D%3F%5B0-9%5D%7B4%7D%24%2Fgm https://regexper.com/#%2F%5E(1%5Cs%3F)%3F(%5B0-9%5D%7B3%7D%7... From https://www.freecodecamp.org/challenges/validate-us-telephone-numbers https://www.freecodecamp.org/challenges/validate-us-telephon... I found these 11 videos most helpful when learning regex from codecourse https://www.youtube.com/watch?v=GVZOJ1rEnUg&index=1&list=PLfdtiltiRHWGRPyPMGuLPWuiWgEI9Kp1w https://www.youtube.com/watch?v=GVZOJ1rEnUg&index=1&list=PLf...