fun <T, R> Iterable<T>.blockBy(transform: (T) -> R): List<List<T>> {
	val iter = iterator()
	if (!iter.hasNext())
		return emptyList()
	val start = iter.next()
	var key = transform(start)
	var count = mutableListOf<T>(start)
	val ret = mutableListOf<List<T>>()
	for (i in iter) {
		val ikey = transform(i)
		if (key == ikey)
			count.add(i)
		else {
			ret.add(count)
			key = ikey
			count = mutableListOf<T>(i)

		}
	}
	return ret
}