Non-FP Kotlin makes easy uses of `require()`, `che...

# arrow

[CLOVIS]

Non-FP Kotlin makes easy uses of require(), check() and error() to shortcut execution. Either is much more “precise” and “safe”, however I don't know how to write something as concise and readable:

fun foo(param: Int) {
  require(param > 1) { "Some message here" }

doSomething() ?: error("that's not possible")
}

I guess the either block should help with this, but I don't really see how to use it for these cases.

[CLOVIS]

Maybe adding a function like this?

fun <L> requireEither(cond: Boolean, block: () -> L): Either<L, Unit> =
  if (cond) Right(Unit)
  else Left(block())

This function would be used in an either block exactly as the current require function is used.

Obviously the name is bad, but apart from that, what do you think?

[CLOVIS]

They could probably be made inline as well, but yeah I'd love to have access to those ^^

[simon.vergauwen]

Yes, can be made inline too 😄

[simon.vergauwen]

Adding them locally for now would be super easy as you can see

[CLOVIS]

Yep, I'm probably going to add them in my projects because they make validation much, much nicer than having ifs inside of ifs. Without either I would've used early returns, but those are not available everywhere (inside crossinline lambdas for example)

[simon.vergauwen]

Yes, I think it makes a lot of sense too! Feel free to add a ticket on the Arrow repo 😉

[simon.vergauwen]

@CLOVIS https://github.com/arrow-kt/arrow/pull/2449

[CLOVIS]

Nice! That looks really good

[simon.vergauwen]

Feel free to comment any feedback on the PR! Really awesome suggestion 🙏