nrinaudo/kantan.regex

Regular expression library for Scala

Nicolas Rinaudo

@nrinaudo

ok, so I just re-read that example, and it was a mistake on my part to use ordered in the documentation. I should have used decoder. I'll create an issue

rubenpieters

@rubenpieters

thats pretty cool

Nicolas Rinaudo

@nrinaudo

is it clear what MatchDecoder.decoder does, and that it supports any arity from 1 to 22, or do you need some help?

rubenpieters

@rubenpieters

yes that is clear, but since it takes implicit groupdecoders it wont work when I will put multiple case class in it, is that right?

Nicolas Rinaudo

@nrinaudo

(just got pulled in on a meeting)

rubenpieters

@rubenpieters

ok nevermind the previous comment, I understand a bit better what it does now, the .decoder thing is a nice solution for the user to specify the order of things he wants to do

Nicolas Rinaudo

@nrinaudo

or build nested case class structures

rubenpieters

@rubenpieters

yep

Nicolas Rinaudo

@nrinaudo

I assumed that was your workaround :)

rubenpieters

@rubenpieters

Well currently the workaround is that I split the string and parse those elements separately in the case classes I want. I'm not sure the .decoder would work since in total there are more than 22 fields

Nicolas Rinaudo

@nrinaudo

ah, I see

Nicolas Rinaudo

@nrinaudo

Alright, so kantan.codecs now has support for java 8 times. I need to tidy it up somewhat, but it should now be trivial to bring it to kantan.regex

rubenpieters

@rubenpieters

Ok cool thanks

Nicolas Rinaudo

@nrinaudo

0.1.6-SNAPSHOT is being published just now, with support for java8 dates. I've yet to write the documentation, but importing kantan.regex.java8._ will bring default instances in scope

if the default java formats are not what you're after, you can declare your own decoders through instantDecoder, localDateTimeDecoder, .... which all take a DateFormat as a parameter

rubenpieters

@rubenpieters

Ill try to take a look at that tomortow

Nicolas Rinaudo

@nrinaudo

no hurry. I need to bring support to kantan.xpath and kantan.csv, and write the documentation, before a proper release anyway

plus, you already have a working solution which is essentially the same code, so it's not like you have a burning need to upgrade

rubenpieters

@rubenpieters

thats true

Nicolas Rinaudo

@nrinaudo

@/all official artifacts for 0.1.6 are now available on maven central.

johannes karoff

@cornerman

hi there! is it possible to concatenate two existing Regex into one Regex, which parses a tuple of the individual results?

Nicolas Rinaudo

@nrinaudo

Not directly, because two regexes mean two evaluations which is not supported by the decoder mechanism

On the other hand, you can use the decoding mechanism to yield two results, then manually conpose them into a tuple using flatmap

johannes karoff

@cornerman

@nrinaudo thanks for the response! how would i go about doing that? :)

Nicolas Rinaudo

@nrinaudo

sorry, missed your message.
So the principle is fairly straightforward - each evaluation yields an Either[Error, A], so you could write something like:

for {
  i <- str.evalRegex[Int](regex1)
  b <- str.evalRegex[Boolean](regex2)
} yield (i, b)

where regex1 and regex2 are the two regular expressions you with to compose and strthe string you wish to apply them to

@cornerman let me know if this isn't clear enough. If you were to give me a concrete use case, I could probably wip up some quick code to show you

johannes karoff

@cornerman

@nrinaudo ah got you. thats what you meant with decoding mechanism :)

my use-case is parsing a url-like structure. so I have a website, where i need to interpret the url (or more specifically the hash part of the url). so i have something similar to query parameters or key-value pairs like something=false&list=1,2,3&nothing=. so depending on the key, i need to interpret the rhs differently.

i was using fastparse previously to have a grammer for the options in the url. so i could write a parser for each option and then combine them in one grammar. that was nice. but is very slow on startup in scala.js.

johannes karoff

@cornerman

what i am doing now: i take the url and first match Map[String ->String] with a simple regex for k=v. and then i parse each entry in the map. so in the example, i would have then a regex for something, list and nothing.

so, it works now :)

johannes karoff

@cornerman

on another note: when i was using a star in my regex, e.g. (\w+)(:\d+)*. and then compiled a Regex[(String,String)] or Regex[(String,Seq[String])], I always got an error about an "empty group". I then went for (\w+)(:\d+)*? and used Regex[(String, Option[String])]. what can i do about this?

Nicolas Rinaudo

@nrinaudo

@cornerman Not sure about your use case for URI parsing, I would probably use a dedicated library for that as URI parameter parsing isn't as trivial as it might seem at first glance

johannes karoff

@cornerman

@nrinaudo in general i agree but it is not really a url. we have a SPA app running in the browser, which writes its current options to the hash-part of the url. the options are key-value pairs and similar to an url with regards to being a sequence of key-value pairs separated by & and =. so a dedicated uri parsing library would not really fit.

Nicolas Rinaudo

@nrinaudo

and as for your example, I'll need to see your code, because I don't think I understand what you're saying:

"abc:123".evalRegex[(String, String)](rx"(\w+)(:\d+)*").next
res1: kantan.regex.DecodeResult[(String, String)] = Right((abc,:123))

johannes karoff

@cornerman

yes, your example works, but if you have no match for (:\d+)*, it does not work:

"abc".evalRegex[(String, String)](rx"(\w+)(:\d+)*").next
res1: kantan.regex.DecodeResult[(String, String)] = Left(EmptyGroup: an empty group was found)

Nicolas Rinaudo

@nrinaudo

well yeah - the second group is not matched

so you get a match with a single group, which is what this is telling you

you have basically two choices there:

make the second group optional
make slightly more complicated groups (this would also allow you to ignore the :, which I'm assuming is desirable but I might be wrong)

johannes karoff

@cornerman

but semantically an empty string is a match for something* in a regex, isn't it?

Nicolas Rinaudo

@nrinaudo

you don't have an empty string. You have nothing

wait, what do you think the : means in your regex?

is that a separator, or did you think it means "non-capturing group"?

johannes karoff

@cornerman

no, just a separator

Nicolas Rinaudo

@nrinaudo

right

johannes karoff

@cornerman

i was under the impression, i could have a Regex[(String, Option[String])] from a *. just like from a ?. because both can yield an empty result

Nicolas Rinaudo

@nrinaudo

so then:

"abc:".evalRegex[(String, String)](rx"(\w+)(:\d*)").next

johannes karoff

@cornerman

but that is not what I want to match

Nicolas Rinaudo

@nrinaudo

but let's take it from the top. What are you precisely trying to do?

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