Scala - increasing prefix of a sequence

Question

I was wondering what is the most elegant way of getting the increasing prefix of a given sequence. My idea is as follows, but it is not purely functional or any elegant:

Answer 1

You can take your solution, @Samlik, and effectively zip in the currentElement variable, but then map it out when you're done with it.

sequence.take(1) ++ sequence.zip(sequence.drop(1)).
    takeWhile({case (a, b) => a < b}).map({case (a, b) => b})

Also works with infinite sequences:

val sequence = Seq(1, 2, 3).toStream ++ Stream.from(1)

sequence is now an infinite Stream, but we can peek at the first 10 items:

scala> sequence.take(10).toList
res: List[Int] = List(1, 2, 3, 1, 2, 3, 4, 5, 6, 7)

Now, using the above snippet:

val prefix = sequence.take(1) ++ sequence.zip(sequence.drop(1)).
    takeWhile({case (a, b) => a < b}).map({case (a, b) => b})

Again, prefix is a Stream, but not infinite.

scala> prefix.toList
res: List[Int] = List(1, 2, 3)

N.b.: This does not handle the cases when sequence is empty, or when the prefix is also infinite.