My guess is, that someone started with a small share of features to find a simple solution for the problem, but the complexity of the problem got waaaay out of hand.
Regex is actually just a way to write (Epsilon) non determistic state automata(ε-NDA) using text! ε-NDA comes from automata theory and they are just a somewhat powerful way to describe state machines!
They can kind of be seen as a stepping stone to things like Context-Free Grammars which is what language parsers use to define their language/parsers, and Turing machines! Regex is a fundamental part of computer science, and they are of course incredibly useful in string validation due to their expressive power!
If you study at uni and get the chance to take a course in automata theory I recommend it! Personal favorite subject :)
Regexes are actually used in formal computer science (if that’s the right term), i.e. “proof that this and that algorithm won’t deadlock” or something like that.
They’re actually really elegant and can cover a lot. But you’ll have to learn them by using them.
You are probably thinking of Temporal logic which allows us to model if algorithms and programs terminate etc! It can be represented by using state machines tho!
It’s been a while, so I’m quite rusty, especiallyeon the terminology, but I think we modelled feasible sequences of finite and infinite state machines using regexes.
For the purpose of algorithm verification, the final and/or pushdown automaton or probably sometimes even Turing Machines are used, because they are easier to work with. “Real” regular expressions are only nice to write a grammar for regular languages which can be easily interpreted by the computer I think. The thing is, that regexs in the *nix and programming language world are also used for searching which is why there are additional special characters to indicate things like: “it has to end with …” and there are shortcuts for when you want that a character or sequence occurs
at least once,
once or never or
a specified number of times
back to back.
In “standard” regex, you would only have
() for grouping,
* for 0 or any number of occurances (so a* means blank or a or aa or …)
+ as combining two characters/groups with exclusive or (in programming, a+ is mostly the same as aa* so this is a difference)
and sometimes some way to have a shortcut for (a+b+c+…+z) if you want to allow any lower case character as the next one
So there are only 4 characters which have the same expressive power as the extended syntax with the exception of not being able to indicate, that it should occur at the end or beginning of a string/line (which could even be removed if one would have implemented different functions or options for the tools we now have instead)
I am, and I can think of many cases where plain dumb string matching since you know what you’re dealing with beats regex in both performance and maintainability.
You’re a clown that wouldn’t know how to compare two strings without regex even if you got paid 6 figures to do it.
There’s a lot of use cases where regex makes a lot of sense: complex log parsing, determining if a value entered is a valid phone number or email, syntax highlighting, data validation in ML preprocessing, etc. A lot of languages also come with certain features that allow regex to be more efficient than dumb string matching, such as the ability to pre-compile patterns and the flexibility of being able to choose between deterministic and non-deterministic finite automata, should you need efficiency for one use case and flexibility for another. It really depends on what you’re designing and how it’s going to be used, of course.
It explains all parts of your regex and highlights all matches in your example text. I usually add a comment to a regex101 playground if I use a regex in code.
I have written dozens upon dozens of Regexes without using reverse negative lookups, but I guess according to you I don’t really know Regexes because I haven’t used those specific features?
You don’t need to know all about a subject to know a subject.
It’s pattern-matching. Like searching *.txt to get all text files. It’s just… more. There’s symbols for matching the start of a string, the end of a string, a set of characters, repetition, etc. Very “etc.” And the syntax blows. The choices of . for match-any-character and * for zero-or-more really fuck with common expectations.
It can also replace substrings that match. Like changing the file extension of all text files. Where it gets properly difficult is in “capture groups.” Like looking for all file extensions, and sticking a tilde after the dot. You can put parentheses around part of the pattern being matched and then reference that in the replacement. Conceptually simple - pain in the ass to use properly - syntax both sucks and blows.
Lookahead is what you do to match “ass” but not “assault.” I refuse to elaborate further.
I don’t agree that AI has no uses, you just have to know when to use it. There are multiple times I have scoured documentation and official forums of a niche tool to few results only to ask ChatGPT and get far closer to my goal in 2 minutes than I did in 30. I know the AI has to be getting that info from somewhere, but if Google, Reddit, and a forum search can’t find it then I am sorry but I am going to ask an AI.
I got the “error in moderation” today today too when I asked it to make me a ghost with the beard and body type of Santa Claus. Like it knows Santa is not a real person right?
You are not logged in. However you can subscribe from another Fediverse account, for example Lemmy or Mastodon. To do this, paste the following into the search field of your instance: !programmerhumor@lemmy.ml
Post funny things about programming here! (Or just rant about your favourite programming language.)
Rules:
Posts must be relevant to programming, programmers, or computer science.
No NSFW content.
Jokes must be in good taste. No hate speech, bigotry, etc.
You have a problem. You decide to use regex to solve it. Now you have two problems.
I still don’t understand regex at all
My guess is, that someone started with a small share of features to find a simple solution for the problem, but the complexity of the problem got waaaay out of hand.
Regex is actually just a way to write (Epsilon) non determistic state automata(ε-NDA) using text! ε-NDA comes from automata theory and they are just a somewhat powerful way to describe state machines! They can kind of be seen as a stepping stone to things like Context-Free Grammars which is what language parsers use to define their language/parsers, and Turing machines! Regex is a fundamental part of computer science, and they are of course incredibly useful in string validation due to their expressive power! If you study at uni and get the chance to take a course in automata theory I recommend it! Personal favorite subject :)
Regexes are actually used in formal computer science (if that’s the right term), i.e. “proof that this and that algorithm won’t deadlock” or something like that.
They’re actually really elegant and can cover a lot. But you’ll have to learn them by using them.
You are probably thinking of Temporal logic which allows us to model if algorithms and programs terminate etc! It can be represented by using state machines tho!
It’s been a while, so I’m quite rusty, especiallyeon the terminology, but I think we modelled feasible sequences of finite and infinite state machines using regexes.
That’s how I was forced to learn 'em in uni. ;)
Ohhh I must be confusing the two! But yea, Regex is just NDAs in text form! The course I have had on it is one of my favorites! Really fun stuff
For the purpose of algorithm verification, the final and/or pushdown automaton or probably sometimes even Turing Machines are used, because they are easier to work with. “Real” regular expressions are only nice to write a grammar for regular languages which can be easily interpreted by the computer I think. The thing is, that regexs in the *nix and programming language world are also used for searching which is why there are additional special characters to indicate things like: “it has to end with …” and there are shortcuts for when you want that a character or sequence occurs
In “standard” regex, you would only have
So there are only 4 characters which have the same expressive power as the extended syntax with the exception of not being able to indicate, that it should occur at the end or beginning of a string/line (which could even be removed if one would have implemented different functions or options for the tools we now have instead)
So one could say that *nix regex is bloated /s
Nobody does.
deleted by creator
deleted by creator
//////?-.,", duh,?!
What part do you not understand?
.*
So you do not understand nothing? That’s great to hear.
No, No, they don’t understand everything and nothing!
Both statements match 😄
Yes
It’s really not too bad as long as:
you use a proper IDE (e.g. Regex101) with highlighting and piecewise explanations
you use named capturing groups
you give the regex a descriptive name in your code
People write regex in notepad and complain it doesn’t work on the first try…
Regexes are write-only. No one can understand other peoples regexes
That’s why they don’t belong anywhere outside single line bash commands.
deleted by creator
Use of regex in production code is a sign of incompetence.
deleted by creator
He’s a troll. He said earlier today that the holocaust wasn’t bad because “not all the jews died”
He’s just trying to pick a fight
I am, and I can think of many cases where plain dumb string matching since you know what you’re dealing with beats regex in both performance and maintainability.
You’re a clown that wouldn’t know how to compare two strings without regex even if you got paid 6 figures to do it.
There’s a lot of use cases where regex makes a lot of sense: complex log parsing, determining if a value entered is a valid phone number or email, syntax highlighting, data validation in ML preprocessing, etc. A lot of languages also come with certain features that allow regex to be more efficient than dumb string matching, such as the ability to pre-compile patterns and the flexibility of being able to choose between deterministic and non-deterministic finite automata, should you need efficiency for one use case and flexibility for another. It really depends on what you’re designing and how it’s going to be used, of course.
deleted by creator
That’s also 'cause other people’s regex are garbage!
Not only other people’s regexes. Mine from last week and before too
Haha
I recommend using https://regex101.com/
It explains all parts of your regex and highlights all matches in your example text. I usually add a comment to a regex101 playground if I use a regex in code.
deleted by creator
I taught myself Regex using Regex101, so something doesn’t add up here.
deleted by creator
Does every Regex contain a reverse negative lookup? Do I need to know how to do a reverse negative lookup to write a Regex?
If not, why are you asking?
deleted by creator
I have written dozens upon dozens of Regexes without using reverse negative lookups, but I guess according to you I don’t really know Regexes because I haven’t used those specific features?
You don’t need to know all about a subject to know a subject.
Lol. I doubt the inventors of regex know all of regex
I disagree. I found it to be incredibly useful when I knew what regex was and that I needed it, but I couldn’t piece together a single string with it.
deleted by creator
The plural of regex is regrets.
It’s pattern-matching. Like searching
*.txtto get all text files. It’s just… more. There’s symbols for matching the start of a string, the end of a string, a set of characters, repetition, etc. Very “etc.” And the syntax blows. The choices of.for match-any-character and*for zero-or-more really fuck with common expectations.It can also replace substrings that match. Like changing the file extension of all text files. Where it gets properly difficult is in “capture groups.” Like looking for all file extensions, and sticking a tilde after the dot. You can put parentheses around part of the pattern being matched and then reference that in the replacement. Conceptually simple - pain in the ass to use properly - syntax both sucks and blows.
Lookahead is what you do to match “ass” but not “assault.” I refuse to elaborate further.
Regex’s are not something you need AI for as there are already tools that explain them for you. Use regexr.com or a similar tool.
Yeha, also anything else has plenty of books and internet content on them so you really don’t need AI for those too.
Foxes
Boxes
Hexes
Regexes
You can do it. You too can pluralize without an apostrophe.
I’ve begun to understand that the modern meaning of an apostrophe is “oh shit! Here comes an ‘s’”.
Sadly, I am gradually growing okay with that idea.
Thanks for pointing that out, it’s a bad habit I’ve picked up!
Oxen
Children
Brethren
Regexen
____ are not something you need AI for as there are already tools that explain ____ for you. Use Wikipedia or a similar tool.
I don’t agree that AI has no uses, you just have to know when to use it. There are multiple times I have scoured documentation and official forums of a niche tool to few results only to ask ChatGPT and get far closer to my goal in 2 minutes than I did in 30. I know the AI has to be getting that info from somewhere, but if Google, Reddit, and a forum search can’t find it then I am sorry but I am going to ask an AI.
With an explanation like this, I thing I’ll take the AI.
I got the “error in moderation” today today too when I asked it to make me a ghost with the beard and body type of Santa Claus. Like it knows Santa is not a real person right?
Ya, it’s a generic error from the looks of it. Didn’t know what error to throw when it went down, so it appears to have defaulted to this.
Could have been worse. Could have been an Error in Excess.
This is proof that regex even confuses the bots.
May be our own path to survive the AI rebellion.
Maybe the goal wasn’t to stop the AIs but the aaaaaaaaaaaaaaaaaaaaaaaa! we made along the way.
(For reference: https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS)
deleted by creator
Regex can be explained? I thought it was all just arcane runes, only understood by the 60 year old unix wizards, who created it in the 1st place…