Fib.kt

fun main(args: Array<String>) {
    println(fib().take(5).toList())
}

fun fib() = sequence<Int> {
    yield(1)
    yield(1)
  
    var prev = 1
    var prevPrev = 1
    while (true) {
        val cur = prevPrev + prev
        yield(cur)
        
        prevPrev = prev
        prev = cur
    }
}