Scala에 주요 기능들 혹은 샘플 소스 ^^

이번에는 주요 기능들이라기 하기 모한 샘플 소스들 입니다. 보고 이해 하세요 ^^

Abstract Types

object abstractTypes extends Application {

  abstract class Buffer {

    type T; val element: T

  }

  abstract class SeqBuffer {

    type T; val element: Seq[T]; def length = element.length

  }

  def newIntBuffer(el: Int) = new Buffer {

    type T = Int; val element = el

  }

  def newIntBuffer(el: Int*) = new SeqBuffer {

    type T = Int; val element = el

  }

  println(newIntBuffer(1).element)

  println(newIntBuffer(1, 2, 3).length)

}

Result:
1
3

BigInt

/** Bigint's can be used seamlessly */

object bigint extends Application {

  def factorial(n: BigInt): BigInt =

    if (n == 0) 1 else n * factorial(n-1)


  val f50 = factorial(50); val f49 = factorial(49)

  println("50! = " + f50)

  println("49! = " + f49)

  println("50!/49! = " + (f50 / f49))

}

Complex Operations

object complexOps extends Application {
  class Complex(val re: Double, val im: Double) {
    def + (that: Complex) =
      new Complex(re + that.re, im + that.im)
    def - (that: Complex) =
      new Complex(re - that.re, im - that.im)
    def * (that: Complex) =
      new Complex(re * that.re - im * that.im,
                  re * that.im + im * that.re)
    def / (that: Complex) = {
      val denom = that.re * that.re + that.im * that.im
      new Complex((re * that.re + im * that.im) / denom,
                  (im * that.re - re * that.im) / denom)
    }
    override def toString =
      re + (if (im < 0) "-" + (-im) else "+" + im) + "*i"
  }
  val x = new Complex(2, 1); val y = new Complex(1, 3)
  println(x + y)
}

For and Yield

/** Turn command line arguments to uppercase */

object Main {

  def main(args: Array[String]) {

    val res = for (a <- args) yield a.toUpperCase

    println("Arguments: " + res.toString)

  }

}

Extend Builtins

/* Adding ! as a method on int's */

object extendBuiltins extends Application {

  def fact(n: Int): BigInt =

    if (n == 0) 1 else fact(n-1) * n

  class Factorizer(n: Int) {

    def ! = fact(n)

  }

  implicit def int2fact(n: Int) = new Factorizer(n)


  println("10! = " + (10!))

}

Maps

/** Maps are easy to use in Scala. */

object Maps {

  val colors = Map("red" -> 0xFF0000,

                   "turquoise" -> 0x00FFFF,

                   "black" -> 0x000000,

                   "orange" -> 0xFF8040,

                   "brown" -> 0x804000)

  def main(args: Array[String]) {

    for (name <- args) println(

      colors.get(name) match {

        case Some(code) =>

          name + " has code: " + code

        case None =>

          "Unknown color: " + name

      }

    )

  }

}

Implicits

/* Defines a new method 'sort' for array objects */

object implicits extends Application {

  implicit def arrayWrapper[A : ClassManifest](x: Array[A]) =

    new {

      def sort(p: (A, A) => Boolean) = {

        util.Sorting.stableSort(x, p); x

      }

    }

  val x = Array(2, 3, 1, 4)

  println("x = "+ x.sort((x: Int, y: Int) => x < y))

}

Match Arguments

/** Basic command line parsing. */

object Main {

  var verbose = false


  def main(args: Array[String]) {

    for (a <- args) a match {

      case "-h" | "-help"    =>

        println("Usage: scala Main [-help|-verbose]")

      case "-v" | "-verbose" =>

        verbose = true

      case x =>

        println("Unknown option: '" + x + "'")

    }

    if (verbose)

      println("How are you today?")

  }

}

Primes

/** Print prime numbers less than 100, very inefficiently */

object primes extends Application {

  def isPrime(n: Int) = (2 until n) forall (n % _ != 0)

  for (i <- 1 to 100 if isPrime(i)) println(i)


}

Sum Arguments

object Main {

  def main(args: Array[String]) {

    try {

      val elems = args map Integer.parseInt

      println("The sum of my arguments is: " + elems.foldRight(0) (_ + _))

    } catch {

      case e: NumberFormatException => 

        println("Usage: scala Main <n1> <n2> ... ")

    }

  }

}

Varargs

/** Using Java varargs */

object varargs extends Application {

  val msg = java.text.MessageFormat.format(

    "At {1,time} on {1,date}, there was {2} on planet {0}.",

    "Hoth", new java.util.Date(), "a disturbance in the Force")

  println("Message="+msg)

}

아무래도 윈도우 용이겠죠? :)?


다음과 같이 실행해 보세요 ^^


> mkdir classes

> scalac -d classes %SCALA_HOME%\doc\scala-devel-docs\scala\examples\sort.scala

> scala -cp classes examples.sort

[6,2,8,5,1]


[1,2,5,6,8]


다음화에서 고급용으로 ^^