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Comment by crazygringo | Hacker News Reader

> Regular expressions is a great tool for searching patterns in text. But I always found it unnatural for text editing.

The entire purpose of this project seems to hinge on this assertion, but there isn't a single example.

I don't understand what makes regex unnatural for editing? What is meant by editing? Why do people struggle with groups?

There are lots of examples of the syntax for this project, but why is it better than regular regex?

If there were a few examples showing "here's the vanilla regex version, here's my version, here's why my version makes this easier" I might be able to understand this project.

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I would say regex is usually pretty write once edit never. Building a prototype that tries to look beyond that is a great way to see what a better future might look like in this regard.

Sure, though you can do commented regexp in Perl and Ruby and probably others, using x flag if my memory serve well, though in practice for maintenability you'll probably better avoid this kind of "clever" tricks.

Just skimming through the readme, I'm also in doubt that the paradigm shift would really be any better than folk regexp.

That doesn't make the existence of the project any less cooler, of course. Congratulation to the author, and don't let such a comment narrow down your motivation, as it's really not the point. If you enjoy do it, great. If you learn something in the process, awesome. If it can lead to something that I can't envision, how marvelous. But it doesn't, that was still a great epic and you can be proud.

Oh, I've learnt a lot. Initially wanted to complete the whole project in two weeks and it took a few months. The hardest part was the DFT determinization algorithm design.

Thanks for your feedback!

Fair point. The most explicit example if you need to change something in context. For example if we need to change 'y' to 'Y' only if it occurs between x and y you would do something like this in python.

pattern = r'(x)y(z)'

replacement = r'\1Y\2'

result = re.sub(pattern, replacement, text)

I would like to replace it with 'xy:Yz' pattern:

result = re.trre('xy:Yz', text)

If you need your x, z to be more complicated patterns or even regex themselves it can be more handy using this approach.

Thanks!

I guess I'm still struggling to see how it's simpler overall.

Most of the examples on your page don't involve groups at all, e.g.:

  $ echo 'catcatcat' | trre '((cat):(dog))*'
  dogdogdog

That already seems a lot more complicated than just:

  re.sub('cat', 'dog', 'catcatcat')

I don't need to use groups that often in regex replacements, and when I do I'm already trying to do something complicated, and it's not clear to me why the colon syntax is easier to write, easier to understand, or if it's as flexible.

Not trying to criticize the project, just genuinely trying to understand the specific strengths and limitations of the proposed syntax. E.g. what if I want to turn xyz into zYx?

>> E.g. what if I want to turn xyz into zYx?

echo 'zyx' | ./trre 'xy:Yz|zy:Yx'

It is still a regular language. I do not introduce references.

You are right in sense the `sed` is far superior editor. But here I see some advantages: - the current implementation is super small; it is direct translation to an automaton - the complex patterns may be compiled in a more efficient way using deterministic transducer. I can't defend this claim now but I have some evidences - there are some tricks you can do using 'generative' part of it, e.g. and you even can find levenshtein distance of 1 between two strings just by generating substitutions/insertions/deletions and implement a simple spell checker.

Overall, I think you have a good point. Maybe it is just marginal improvement (if any). It was more comfortable to write in this style instead of group usage. I used it for some time and found it handy (especially as extended `tr`).

I think it's an interesting project, but is this a functional replacement for regex substitutions? It seems like you can only replace text with something else at the same location. Separating the replacement from the matching can be unweildy, but you can reorder, repeat, and insert text between things too.

IIUC

Well, I think it is fair to say that regexes alone do not provide any facilities for editing. You have groups, but you have to use some other language (like sed) to compose those groups.

Come on, it's about replacements. They're easier to express (meaning literally easier to type out) with the author's syntax

Great project

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