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Comment by lucideer | Hacker News Reader

I've yet to meet anyone who thinks this.

The greatest problem with regexp is not its complexity nor learning curve: it's its apparent complexity & learning curve. That tends to put learners off, but anyone I know who's persisted has found the journey faster than expected. After they're over it, everyone I've talked to thinks pretty highly of the syntax: it's simple (small set of compostable components) & expressive, especially if using labelled groups.

The second greatest problem with Regexp is learning query optimisation: that's definitively complex but this new syntax doesn't even attempt solving that.

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Eh, I can manage to write a regexp with a little effort, but reading them has never stopped being painful. So in my anecdotal, sample-size one experience it leans heavily towards write-only language.

This might do better there.

Do you use the /x modifier?

Meet me. I think it. Now you've met one.

You can of course disqualify me in saying I can't possibly have persisted at learning it, if I don't like it. But I am inevitably "the guy who knows regular expressions" in the places I've worked. I do use them, for stuff like fixing tedious one-off data munging jobs without having to write an actual program to do it. But I

* Do it step by step, to avoid writing anything resembling a complex regex, because I've yet to meet anyone who can write a complex regexp without bugs.

* Use "undo" a lot in that process.

> I've yet to meet anyone who thinks this.

Hello *waves*

The only thing regexp has on the plus side is that it's compact. I'd prefer something that's more readable without knowledge. I know how to use it but I always have to google it. I only use it once per year and so there's no big win in mesmerizing it.

Do you remember at least:

  . * | + ? ( )

This is 95% of it. After that, it's character classes and lazy matching.

Character classes can often be given as ranges:

  [a-z] [A-Z] [0-9] ^ $

You can use the pipe | to combine then.

Lazy matching finds the shortest matching string instead of the longest one. This is given by the symbols:

  *? +?

Instead of + and * respectively.

> I only use it once per year

If you use a text editor, any kind of repetitive find+replace activity can be sped up using regexes. Seems strange you only use it once per year.

Some people tell you that you can't parse XML using regexes. THEY'RE WR- right, but you can often do decent one-off jobs on an XML document using regular expressions, as long as you're aware that it's a one-off job that won't work on any other document.

It is not that it is hard to understand the syntax or even write them, it is hard to read and change them. Here is an example I just grabbed off a random webpage:

^(?=.\d)(?=.[a-z])(?=.[A-Z])(?=.[!@#$^&()_-]).{8,18}$

That is hard to quickly* read and understand what it is. Sure a comment would help, but if someone said it isn't working, I have to work all that out and then fix it.

There is a reason Perl lost to Python. It just seems like we can do better.

And that's an expression without any escaped parens, braces, etc.

> compostable components

I've certainly seen regexes that remind me of compost heaps.

(I agree that regex syntax is fine. I just liked the typo.)

> The second greatest problem with Regexp is learning query optimisation: that's definitively complex but this new syntax doesn't even attempt solving that.

Query optimisation is totally unnecessary if you use Rust's or Go's implementation.

:grimace_face:

I'm a big believer that "premature optimisation" is a bad thing but making a blanket statement that any given implementation is 100% performant for all use-cases is going a bit far.

I doubt whatever you're doing is going to work in Rust or Go.

Say that the length of your string is n, and the length of your regular expression is m. Isn't Regular Expression matching in those languages guaranteed O(m n) time? In plain English, that's only linear time - which you practically can't improve on - even if you tried! It can only do worse if your implementation uses backtracking instead of Finite Automata - which was very common at one time, but is now considered The Wrong Way: https://swtch.com/~rsc/regexp/regexp1.html

There is actually a way to optimise your queries, which is by precompiling them to DFAs, but I don't think that's what you're doing.

I stand completely corrected. This is cool.

> There is actually a way to optimise your queries, which is by precompiling them to DFAs, but I don't think that's what you're doing.

You can do that, but the primary advantage of DFAs in practice is backtracking avoidance, so simply reduction of backtracking in manually constructed queries is more what I was referring to. The missing part of the puzzle here being that not supporting backtracking at all doesn't limit capabilities, so removal rather than reduction is the go/rust approach.

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