How do I split a String and keep the delimiters?

I keep getting "type mismatch" when trying to use a Seq[Seq[String]] in Scala. Why?

• Here's my code. class Board (rows: String*) { var cells: Seq[Seq[String]] = rows.map(_.split("")) override def toString() = { for (rows <- cells) for (row <- rows) Console.println(row) } } I don't understand why I get this error: error: type mismatch;  found   : Unit  required: java.lang.String     for (rows <- cells) Why is "cells" now a Unit? And why does it require a String for a for loop?

• Answer:

  I figured it out, by the way. The problem is that by default, the "for" loop returns type Unit. If you want it to return an array, then you have to use yield. Also, I found that for was a bad choice for a toString method anyway. My new code is this:   override def toString: String =     "[[" + cells.map(_.mkString(", ")).mkString("]\n [") + "]]\n"