Can you rewrite this to produce “combinations” for any nonzero value of “numDice”? (This is mostly academic curiosity.)

gistfile1.scala

  val combinations: Seq[Seq[Int]] = numDice match {
    case 1 => for (a <- 1 to numSides) yield Seq(a)
    case 2 => for (a <- 1 to numSides; b <- 1 to numSides) yield Seq(a, b)
    case 3 => for (a <- 1 to numSides; b <- 1 to numSides; c <- 1 to numSides) yield Seq(a, b, c)
  }

Can't help with Scala (been away too long), but here's a way to do it in Clojure:

(defmacro die-rolls [num-dice num-sides]
  (let [sides (vec (range 1 (inc num-sides)))
        die-names (vec (repeatedly num-dice gensym))
        die-bindings (vec (mapcat #(list % sides) die-names))]
    `(for ~die-bindings
       ~die-names)))