min-dist.scala

val arr = Array(2, 4, 5, 19, 21, 28)
val sl = arr.toList.sorted

val dist = sl flatMap { x => 
   sl flatMap { y =>
     if (x != y) {
        if (x < y) List(y - x) 
	else List(x - y)
     }
     else Nil
   }
}

// minimum distance
dist.min