Pascal's Triangle in scala

Pascal.scala

// An exercise using scala to output a nicely formatted Pascal's triangle
import scala.math.max

// Define an extractor for Int so we can match below
object Int {
  def unapply(s:String) : Option[Int] = try {
    Some(s.toInt)
  } catch {
    case _ : java.lang.NumberFormatException => None
  }
}

object Pascal {

  val usage = """
    Usage: Pascal rows
  """
  
  def main(args:Array[String]) {
    if (args.length == 0) 
      println(usage)

    for (a <- args) a match {
      case Int(r) => printTriangle(r)
      case s : String => println(s + " is not a whole number")
    }
  }

  /**
   * Computes the value at row r and column c
   */
  def v(r:Int, c:Int) : Int = 
    if (c == 0) 
      1 
    else 
      v(r, c-1) * (r-c)/c

  def printRow(r:Int, seplen:Int) = {
    for (col <- 0 to r) {
      if (col > 0)
	print(" " * seplen)
      val n = v(r+1, col)
      print((" " * (seplen - n.toString.length)) + n )
    }
    println()
  }

  def printTriangle(rows:Int) = {
    // Figure out how many spaces to separate numbers
    var largest = 1
    for (col <- 0 to rows)
      largest = max(largest, v(rows+1, col))

    val seplen = largest.toString.length
    val sep = " " * seplen

    for (r <- 0 to rows) {
      print(sep * (rows-r))
      printRow(r, seplen)
    }
  }
}