scala - Splitting string into groups

Question

I'm trying to 'group' a string into segments, I guess this example would explain it more succintly

scala> val str: String = "aaaabbcddeeeeeeffg"
... (do something)
res0: List("aaaa","bb","c","dd","eeeee","ff","g")

I can thnk of a few ways to do this in an imperative style (with vars and stepping through the string to find groups) but I was wondering if any better functional solution could be attained? I've been looking through the Scala API but there doesn't seem to be something that fits my needs.

Any help would be appreciated

Answer 1

You can split the string recursively with span:

def s(x : String) : List[String] = if(x.size == 0) Nil else {
    val (l,r) = x.span(_ == x(0))
    l :: s(r) 
}

Tail recursive:

@annotation.tailrec def s(x : String, y : List[String] = Nil) : List[String] = {
    if(x.size == 0) y.reverse 
    else {
        val (l,r) = x.span(_ == x(0))
        s(r, l :: y)
    }
}