I have no idea what this is.

test2.scala

object A {
  def main(args: Array[String]) { println(b(Nil)) }

  def b(list: List[Int]):List[List[Int]] = list match {
    case full if full.size == 8 => List(full)
    case _ => def valid(t:List[Int])(h:Int) = {
        def diagonal(op: (Int,Int)=>Int, n:Int, li:List[Int]): Boolean = li match {
          case Nil => false
          case h :: t => n == h || diagonal(op, op(n,1), t)
        }
        ! (t.contains(h) || diagonal(_+_, h+1, t) || diagonal(_-_, h-1, t))
      }
      (1 to 8 toList).filter(valid(list)).map(n => b(n :: list)).flatten
  }
}