This nQueens solution in Scala is surprisingly verbose compared to the JS versions I've seen. I'm still a beginner though, working through the Coursera class by Martin Odersky.

gistfile1.txt

object nQueens {
  def queens(n: Int): Set[List[Int]] = {
    def placeQueens(k: Int): Set[List[Int]] =
    if (k == 0) Set(List())
    else
      for {
        queens <- placeQueens(k - 1)
        col <- 0 until n
        if isSafe(col, queens)
    } yield col :: queens
    placeQueens(n)
}
Int)Set[List[Int]]

def isSafe(col: Int, queens: List[Int]): Boolean = {
  val row = queens.length
  val queensWithRow = (row - 1 to 0 by -1) zip queens

  queensWithRow forall {
    case (r, c) => col != c && math.abs(col - c) != row -r
   }
 }
Int, queens: List[Int])Boolean

def show(queens: List[Int]) = {
  val lines =
    for (col <- queens.reverse)
    yield Vector.fill(queens.length)("* ").updated(col, "Q ").mkString
    "\n\n" + (lines mkString "\n")
}
List[Int])String

(queens(12) map show) mkString "\n"