http://justindomke.wordpress.com/2008/11/29/mandelbrot-in-scala/ のマンデルブロ集合を描画するプログラムのリファクタ

mandelbrot.scala

import java.io._
import java.lang.Math
import scala.annotation.tailrec


/**
 * ref: http://justindomke.wordpress.com/2008/11/29/mandelbrot-in-scala/
 */
object mandelbrot {
  // tiny complex number class including syntactic sugar for basic operations
  case class Complex(a: Double, b: Double){
    // represents the complex number a + b*i
    def +(that: Complex) = that match { case Complex(x,y) => Complex(a+x,b+y) }
    def *(that: Complex) = that match { case Complex(x,y) => Complex(a*x-b*y,a*y+x*b) }
    def abs = Math.sqrt(this.a*this.a + this.b*this.b)
  }

  def run(n: Int, level: Int) : Seq[Byte] = {
    @tailrec
    def divergenceSpeed(z: Complex, c: Complex, level: Int)(isDiverging: Complex => Boolean): Int = level match {
      case 0 => 0
      case l if isDiverging(z) => l
      case l => divergenceSpeed(z * z + c, c , l-1)(isDiverging)
    }

    def px2axis(x: Int, y: Int, max: Int) = Complex(-2.0 + x*3.0/max, -1.5 + y*3.0/max)

    for {
      y0 <- 0 until n
      x0 <- 0 until n
    } yield {
       val z = Complex(0,0)
       val c = px2axis(x0,y0,n)

       divergenceSpeed(z,c,level){ (_:Complex).abs > 2 } match {
         case 0 => 0.toByte
         case _ => 255.toByte
       }
     }
  }

  def main(args: Array[String]) {
    val level = args(0).toInt
    val pixels = args(1).toInt
    val result = run(pixels, level)
    val out = new FileOutputStream("scalaimage.pgm")
    out.write(("P5\n"+pixels+" "+pixels+"\n255\n").getBytes())
    out.write(result.to[Array])
    out.close
  }
}