Chapter 4: Functional programming in Scala 3

[gvolpe]

Chapter 4: Functional programming in Scala 3

⚠️ Note that the order and number of chapters is not yet fully decided, so expect changes here as well ⚠️

[kyri-petrou]

Hey @gvolpe, really enjoying the book so far!

I have a question regarding the Newtype definitions (apologies in advance if it's mentioned somewhere and I missed it!)

Is there a specific reason that you're using an abstract class instead of a trait? I'm not too well across the internals of Scala so I'm not sure whether there might be some overhead involved with traits that's not an issue when using abstract classes

[gvolpe]

Hi @kyri-petrou ,

When I first wrote that code, there was a slight difference in the generated byte code that made one box and the other not, IIRC. I think that has changed in recent versions of Scala 3, so probably using trait gives us the same results.

Either way, that's code that should belong in a library, given the lack of support for newtypes in Scala 3. I hope we get something equivalent to scala-newtype at some point, so this code can disappear :)

[gvolpe]

That sounds super cool! Have you considered Monix Newtypes as well (also mentioned in the book)? It's not for everyone, and a custom encoding allows you to put default instances you want derived for all newtypes, but worth having a look into it.

[kyri-petrou]

Ah I saw that sentence but for some reason I thought it was an old library, didn't realise it was for Scala 3. Thanks for that, I'll look into it! It seems that it might be a good fit!

On a side-note, what's your preferred method for staying up to speed with recent Scala 3 developments? I've been "Watching" repos of interest on github but I was wondering if there's a board or channel anywhere that people put announcements on new libraries / releases / etc

[gvolpe]

Yes, it works for both Scala 2 and 3, so it's great if you have shared code with different versions!

Nothing I can recommend, unfortunately. It's been a lot of manual work so far, following the right people on Github, Twitter, etc, looking at Scala newsletters, and so on.

[kyri-petrou]

Yeah that does sound like quite a bit of work.

Thanks heaps again for the help!

[cihleman3]

Would object JsonString extends Newtype[String] with CirceSerialization[String] actually work? I thought opaque types cannot be overwritten.