Project Euler Probrem 2

problem2.scala

  /*
  * http://projecteuler.net/problem=2
  * http://odz.sakura.ne.jp/projecteuler/index.php?cmd=read&page=Problem%202
  */
  val fib: List[Int] => List[Int] = {
    case Nil | _ :: Nil => throw new IllegalArgumentException
    case xs @ (a :: b :: tail) => {
      val nextNum = a + b
      if (nextNum >= 4000000) {
        xs
      } else {
        fib(nextNum :: xs)
      }
    }
  }



  fib(List(2, 1)).filter(_ % 2 == 0).sum