count_slowly = fn (
	multiplier: int,
	sleep: fn (milliseconds: int),
	write_line: fn (output: str),
) {
	i = 0

	while i < 10 {
		sleep_time = i * multiplier;

		sleep(sleep_time)
		write_line(i as str)

		i += 1
	}
}

async {
	count_slowly(50, thread.sleep, io.write_line)
	count_slowly(100, thread.sleep, io.write_line)
	count_slowly(200, thread.sleep, io.write_line)
	count_slowly(250, thread.sleep, io.write_line)
}