So `flatMap { buildSequence { }}` actually looks n...

# stdlib

[gildor]

So flatMap { buildSequence { }} actually looks nice for this case and works, you just need coroutines for that:

listOf(2, 3, 4).flatMap { buildSequence {
        yield(it)
        if (it % 2 == 0) yield(-it)
}.toList() }