abstract class JSON
case class JSeq(elems: List[JSON]) extends JSON
case class JObj(bindings: Map[String, JSON]) extends JSON
case class JNum(num: Double) extends JSON
case class JStr(str: String) extends JSON
case class JBool(b: Boolean) extends JSON
case object JNull extends JSON

((1000 to 10000) filter isPrime)(1)

val fruit = Set("apple", "banana", "pear")
val s = (1 to 6).toSet

val nums = Vector(1, 2, 3, -88)
val people = Vector("Bob", "James", "Peter")

def scalaList(xs: List[Double], factor: Double): List[Double] = xs match {
    case Nil => xs
    case y :: ys => y * factor :: scaleList(ys, factor)
}

// 丢失……

package scala
trait Function1[A, B] {
    def apply(x: A): B
}