Chapter6-2.scala

package chapter6

/**
  * Created by hoshi on 1/25/16.
  */
object RangeMain {
  def main(args: Array[String]) {
    // Range
    println(1 to 10)
    println(1 until 10)
    println(1 to 10 by 2)
    println('a' to 'c')
    val x = (1 to 10).toList
    println(x)

    // Stream
    val stream = 1 #:: 2 #:: 3 #:: Stream.empty
    println(stream)
    val stream2 = (1 to Integer.MAX_VALUE - 1).toStream
    println(stream2)
    println(stream2.head)
    println(stream2.tail)

    // Tuples
    //def sumSq(in: List[Double]): (Int, Double, Double) = in.foldLeft((0, 0d, 0d))((t, v) => (t._1 + 1, t._2 + v, t._3 + v * v))
    // more readable
    def sumSq(in: List[Double]) : (Int, Double, Double) = in.foldLeft((0, 0d, 0d)) {
      case ((cnt, sum, sq), v) => (cnt + 1, sum + v, sq + v * v)
    }

    println(sumSq(List(1,2,3,4,5)))
    println(Tuple2(1,2))
    println((1,2))
    println(1 -> 2)

    // Map
    var p = Map(1 -> "David", 9 -> "Elwood")
    println(p)
    p += 8 -> "Archer"
    println(p)
    println(p(9))
    // println(p(88)) // NoSuchElementException
    println(p.get(88))
    println(p.get(9))
    println(p.getOrElse(88, "Nobody"))
    println(1 to 9 flatMap(p.get)) //Vector(David, Archer, Elwood)
    println(1 to 9 map(p.get)) //Vector(Some(David), None, None, None, None, None, None, Some(Archer), Some(Elwood))
    p -= 9
    println(p)
    println(p.values.exists(_.contains("z")))
    p ++= List(5 -> "Cat", 6 -> "Dog")
    println(p)
    p --= List(8, 6)
    println(p)

    def removeInvalid(in: Map[Int, Person]) = in.filter(kv => kv._2.valid)

    // Mutable Collections
    val immutableMap = Map(1 -> "a", 2 -> "b", 3 -> "c")
    val newMap = immutableMap - 1 + (4 -> "d")
    println(newMap)
    println(immutableMap)
    // immutable to mutable
    val mutable = immutableMap.toBuffer
    mutable += (5 -> "e")
    println(mutable)
    // mutable to immutable
    val newMap2 = mutable.toMap
    println(newMap2)

    // mutable.Queue
    var ints = scala.collection.mutable.Queue[Int]()
    ints += 1
    ints += (2, 3)
    ints.enqueue(4)
    println(ints)
    ints.dequeue() //FIFO
    println(ints)

    // mutable.Stack
    val stack = scala.collection.mutable.Stack(1, 2, 3)
    stack.push(4)
    stack.push(5, 6, 7)
    println(stack)
    println(stack.pop) // LIFO
  }
}