Hello, This is my first attempt with the new Arrow...

# arrow

[PhBastiani]

Hello, This is my first attempt with the new ArrowFx DSL 🙂
https://gist.github.com/PhBastiani/9e494f7fd971848296914c775f052cbe
No error/cancellation handling at the moment.
Not sure that my tailrecursive copy method is the most idiomatic.

I noticed a wrong proposal of the IDE: sometimes IntelliJ proposes to remove the suspend modifier when it is necessary 😕
Feedback appreciated !

[stojan]

resourcedCopy can be a suspend function, instead of regular fun returning a suspend lambda 🙂

[PhBastiani]

Yes... fixed ! with the call of use in the main method...
Other point : I don't understand why i cannot write

Resource({ fileConsumer(src) }, InputStream::close)

instead of

Resource({ fileConsumer(src) }, ::close)

like in your video @Jorge Castillo

[Jorge Castillo]

it's a method reference and I think auto wrapping into suspend doesn't work for those, try to have a suspend function that calls InputStream::close and see whether it works

[Jorge Castillo]

My example used a stubbed interface just for the example, like:

class File {
  suspend fun close(): Unit = TODO()

  companion object {
    fun openFile(path: String): File = File()
  }
}

val resources = listOf(
      Resource({ openFile("path1") }, File::close),
      Resource({ openFile("path2") }, File::close),
      Resource({ openFile("path3") }, File::close)
    )

    val fileContents: List<String> = resources.parTraverse(IOPool) { files ->
      files.use { file -> file.toString() }
    }

[simon.vergauwen]

Yes, the problem there is that it’s not the same signature. There is actually a Continuation parameter, so the Kotlin compiler needs to explicitly translate that for you. Which it currently doesn’t support.

That’d be a great and simple use-case for a compiler plugin, which I’d love to use! 😄

[simon.vergauwen]

@PhBastiani the tailrec suspend fun is very idiomatic IMO. I’ve been using it in lost of places already in the library, and also in the stuff I’m currently building on top.

That’s the cool thing about not having the IO wrapper anymore, is that we can use regular tailrec. I’m also going to introduce a PR in the next day to expose trampoline so you could do the same as IO does internally in cases where you cannot write a tailrec function.

[PhBastiani]

Ho yes, the compiler adds a parameter 👌
Yes the Kotlin tailrec works like a charm with your DSL.

[PhBastiani]

Refactored with your suggestions ... wrappers seem to be the right solution to integrate Java classes. Thx