Card deck using case classes

shuffle.scala

import scala.annotation.tailrec

abstract class Suit { val value: Int } 

case object Clubs    extends Suit { val value = 0 }
case object Diamonds extends Suit { val value = 1 }
case object Hearts   extends Suit { val value = 2 }
case object Spades   extends Suit { val value = 3 }

abstract class Rank { val value: Int }

case object Ace   extends Rank { val value = 0 }
case object Deuce extends Rank { val value = 1 }
case object Three extends Rank { val value = 2 }
case object Four  extends Rank { val value = 3 }
case object Five  extends Rank { val value = 4 }
case object Six   extends Rank { val value = 5 }
case object Seven extends Rank { val value = 6 }
case object Eight extends Rank { val value = 7 }
case object Nine  extends Rank { val value = 8 }
case object Ten   extends Rank { val value = 9 }
case object Jack  extends Rank { val value = 10 }
case object Queen extends Rank { val value = 11 }
case object King  extends Rank { val value = 12 }

class Card(val rank: Rank, val suit: Suit) {
    override def toString(): String = {
        rank.toString() + " of " + suit.toString()
    }

    def toId = {
        suit.value * 13 + rank.value
    }
}

object Card {
    def apply(rank: Rank, suit: Suit): Card = {
        new Card(rank, suit)
    }
}

def makeDeck:Seq[Card] = {
    for(
         suit <- List(Clubs, Diamonds, Hearts, Spades);
         rank <- List(Ace, Deuce, Three, Four, Five, Six, Seven, Eight, Nine, Ten, Jack, Queen, King)
     ) yield { Card(rank, suit) }
}

def printDeck(deck: Seq[Card]) = {
    for(card <- deck){ printf("%s\t%s\n", card.toId, card) }
}

def shuffle(deck: Seq[Card]) = {
    require(deck.hasDefiniteSize)
    val (first, last) = deck.splitAt(deck.size / 2)

    @tailrec
    def tail(cards:Seq[(Card, Card)], list: List[Card]): Seq[Card] = {
        if(cards.isEmpty) list
        else {
            var (card1, card2) = cards.head
            tail(cards.tail, list :+ card1 :+ card2)
        }
    }
    tail((first zip last), Nil)
}

var deck = makeDeck

println("Initial Deck")
printDeck(deck)
println()

println("First Shuffle")
var shuffledDeck = shuffle(deck)
printDeck(shuffledDeck)
println()

deck = shuffledDeck
var count = 1

while(count < 8){
    deck = shuffle(deck)
    count = count + 1
}

println("After 8 perfect shuffles")
printDeck(deck)
println()