5 ms·
> the 'yield' keyword Am I missing something here? $ cat fib.kts fun fib() = sequence { var a = 1; var b = 1 while (true) { yield(a) a
by rbehrends 2y ago
> the 'yield' keyword
Am I missing something here?
$ cat fib.kts
fun fib() = sequence {
var a = 1; var b = 1
while (true) {
yield(a)
a = b.also { b += a }
}
}
println(fib().take(10).joinToString(" -> "))
println(fib().first { it >= 50 })
$ kotlin fib.kts
1 -> 1 -> 2 -> 3 -> 5 -> 8 -> 13 -> 21 -> 34 -> 55
55
Of course, yield() is a function in Kotlin, not a keyword, but the same functionality is there.
- yen223 2y agoThe mechanism in Kotlin that allows them to limit yield() to a sequence{} block , without introducing a new keyword, is pretty dang cool.
- rbehrends 2y agoWhat happens under the hood is that a `sequence {}` call creates an instance of `SequenceScope`, which has `yield()` and `yieldAll()` methods. When executing the block, `this` will reference that particular instance and `yield()` is essentially `this.yield()` and will call the method on the scope instance. The actual functionality is then provided by the coroutine system, though a lot of the heavy lifting is done by the optimizer to eliminate all or most of the runtime overhead.
- poikroequ 2y agoI had no idea Kotlin could do this. I never thought to check. I guess with Kotlin being a JVM language, I simply assumed it wasn't possible. Thank you for providing an example because I was a little confused by a couple other comments mentioning yield...