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How up-to-date is "Looking into immutable data with Optics" from <@U0RM4EPC7> from two years ago?

It's fairly up-to-date, but doesn't go super deep. The Optics library hasn't had a lot of change since it was first added in 2017.

So far I've gone through the basics of what `@optic` does to a data class, but I'm not sure how to jump from that to how to 'mutate' trees

It doesn't _mutate_ long story short, it composes function that together build a very complex _copy_ that you would otherwise have to write by hand.

Sorry, I understand it's all just copy, but I'm not sure how you get to actually doing it. We'll see if the video clears that up :slightly_smiling_face:

Ah, that is a bit harder to explain. It also depends heavily on which optic you compose together.

My original goal when I started building Arrow Optics (I named it Optikal at the time) was to understand how optics worked :upside_down_face:

And… did you understand it? :joy:

Am I right to expect that after writing this code:
```@optics
data class Test(val name: String) {
	companion object
}```
I should be able to type:
```Test.name```
or did I forget something?

Yes, I understand it after building it :smile: Yes, you should but you need to setup KSP correctly. Can be a bit tedious.

<https://arrow-kt.io/docs/optics/#step-3-add-the-plug-in-optional>

<https://kotlinlang.org/docs/ksp-quickstart.html#make-ide-aware-of-generated-code>

I _think_ I didn't forget anything? <https://gitlab.com/clovis-ai/advent-of-code-2022/-/blob/master/build.gradle.kts>

Manually adding the generated files to the source files doesn't seem to be necessary anymore

Oh, interesting. No it's impossible to generate code for a private (file) class.

KSP is actually generating Kotlin code? I thought it generated bytecode directly

I guess that's why everyone is waiting for compiler plugins :slightly_smiling_face:

nevermind, adding the generated source sets is still necessary