Join elem with next one in a functional style

Question

I'm trying to find a way to "join"/"groupby" 2 elements in a list as following :

List("a","b","c","d")  -> List("ab","bc","cd")

With a functional style.

Would someone know how to do this?

Need I use reducer, fold, scan, other higher-order function?

Answer 1

Sliding creates subcollections with sliding window, then you just need to map this sublists to strings:

List("a","b","c","d").sliding(2,1).map{case List(a,b) => a+b}

Answer 2

Try

val xs = List("a","b","c","d")
(xs, xs.tail).zipped.map(_ ++ _) // List(ab, bc, cd)

Answer 3

You can use sliding to create a window:

val l = List("a","b","c","d")
val res = l.sliding(2).map(_.reduce(_ + _))
res.foreach(println)

this results with

ab
bc
cd