appendedAll, but there's a
StrictOptimizedIterableOps#concatthat gets mixed in later..
concatenate" implies an order, but the paint's dry on that shed, I'm sure)
SortedSetLike? I see no mention of it in https://github.com/scala/collection-strawman/wiki/FAQ#how-do-i-cross-build-my-project-against-scala-212-and-scala-213
updateInPlaceWith(key: K, f: V => V): this.type?
f: Option[V] => Vor
ifPresent: V => V, ifAbsent: => V
compute) by using
nullif it's absent, but that seems like not a great idea in Scala (arguably not a great idea in Java either)
List(1,2,3,4,5).toIterator.foldLeft(0)(_ + _).takeWhile(_ < 4)ends up with foldLeft working over all elements rather than only the first three.