kmizu

class Foo {
  private def foo {
    Foo.foo
  }
}
object Foo {
  private def foo {
    println("foo")
  }
}

kmizu

def sum[T:Numeric](xs: List[T]): T = {
  val ev = implicitly[Numeric[T]]
  xs.foldLeft(ev.zero){(acc, e) => ev.plus(acc, e)}
}

kmizu

def map[B](f: A => B): Iterator[B] = new Iterator[B] {
  def hasNext = Iterator.this.hasNext
  def next() = f(Iterator.this.next)
}

kmizu

import scala.continuations.ControlContext._
import scala.continuations._
import scala.collection._

/*
 * C#形式のイテレータを表現したトレイト
 */
trait Generator[+A] extends Traversable[A] {
  def moveNext(): Boolean
  def current: A

kmizu

object BinTreeIterator {
  sealed trait Tree
  case class Node(v: Int, l: Tree, r: Tree) extends Tree
  case object Leaf extends Tree

  def toIterator(node: Tree): Iterator[Int] = {
    def toStream(n: Tree): Stream[Int] = n match {
      case Node(v, l, r) => v #:: toStream(l) #::: toStream(r)
      case Leaf => Stream.empty
    }

kmizu

object StreamProblem {
  def main(args: Array[String]) {
    /*
    val large = Stream.continually(new Array[Byte](10000000))
    //Streamのheadをlargeで参照したままになっているので、
    //OutOfMemoryErrorで死ぬ
    large take 100 foreach {bytes=>
      println(bytes)
    }
    */

kmizu

object RightUsageOfStream {
  def main(args: Array[String]) {
    //Stream.continuallyで作成したStreamのheadをローカル変数で
    //参照していないので入力サイズに比例したメモリ領域を食わない
    //ただし、readLine()を生で使って巨大ファイル読むと時間かかるので注意
    Stream.continually(readLine()) foreach {line =>
      //nothing to do
    }
    //OutOfMemoryErrorで死ぬ例(標準入力から読み込んだサイズが大きい場合)
    /*

kmizu

object BinTreeIteratorBenchmark {
  final class BugFixedStreamIterator[A] (private[this] var self: Stream[A]) extends Iterator[A] {
    // A call-by-need cell.
    class LazyCell(st: => Stream[A]) {
      lazy val v = st
    }

    private var these = {
      val stream = self
      val result = new LazyCell(stream)

kmizu

package foo
object clas {
  def main(args: Array[String]) {
    println("Hello")
  }
}

kmizu

package foo
object `class` {
  def main(args: Array[String]) {
    println("foo")
  }
}