Question

I’m trying to wrap my head around functional programming concepts. Consider the problem of removing empty (zero length) Strings from a list

The following is a purely functional implementation in Haskell which is very readable even if you know nothing about the language

removeEmpty            :: [String] -> [String]
removeEmpty []          = []
removeEmpty ([] :strs)  = removeEmpty strs
removeEmpty (str:strs)  = str : removeEmpty strs

Now consider my implementation in Scala

  def removeEmpty(dirty: List[String]): List[String] = {
    if (Nil == dirty)
      dirty
    else {
      if (dirty(0).length() == 0)
        removeEmpty(dirty.tail)
      else
        dirty.head::removeEmpty(dirty.tail)
    }
  }

It does the same thing but has a very procedural feel about it. Is there a more functional way to write the same method in Scala?

Answer 1

def removeEmpty(dirty: List[String]): List[String] = dirty match {
  case Nil      => Nil
  case "" :: xs => removeEmpty(xs)
  case  x :: xs => x :: removeEmpty(xs)
}

Dirk’s answer probably contains the better solution, but my answer is closer to the original, I think.