scalaの勉強会に行ったのでとりあえず、scalaを触ってみた

scala

東京でscalaの勉強会に参加してきました。
http://www.kaigai-engineer.com/blog/?p=59

完全にノリで参加したのですが、
LL Tigerで関数型言語がえらく取り上げられていたこともあるし、
勉強会に参加することでscalaをさわってみよう！という取っ掛かりができた。

ということで、チュートリアルでも読んでみる。
英語はわからないので和訳で。
Tutorial和訳 - プログラミング言語 Scala Wiki - アットウィキ

# cat << _EOD_ > HelloWorld.scala
object HelloWorld {
  def main(args: Array[String]) {
    println("Hello, world!")
  }
}
_EOD_
# scalac HelloWorld.scala
# ls
HelloWorld$.class  HelloWorld.class  HelloWorld.scala
# scala -classpath . HelloWorld
Hello, world!
# cat << _EOD_ > JavaAndScala.scala
import java.util.{Date, Locale}
import java.text.DateFormat
import java.text.DateFormat._

object FrenchDate {
  def main(args: Array[String]) {
    val now = new Date
    val df = getDateInstance(LONG, Locale.FRANCE)
    println(df format now)
  }
}
_EOD_
# scalac JavaAndScala.scala
# scala -classpath . FrenchDate
2 septembre 2010
# scala
Welcome to Scala version 2.7.7.final (OpenJDK Client VM, Java 1.6.0_18).
Type in expressions to have them evaluated.
Type :help for more information.

scala>
  • 数
scala> val x = 2
x: Int = 2

scala> 1+2*3/x
res1: Int = 4

scala> (1).+(((2).*(3))./(x))          
res4: Int = 4

scala> 1.+(2)                
res5: Double = 3.0

scala> (1).+(2)
res6: Int = 3
  • 関数
# cat << _EOD_ > FuncIsObject.scala
object Timer {
  def oncePerSecond(callback: () => Unit) {
    while (true) { callback(); Thread sleep 1000 }
  }
  def timeFlies() {
    println("time flies like an arrow...")
  }
  def main(args: Array[String]) {
    oncePerSecond(timeFlies)
  }
}
_EOD_
# scalac FuncIsObject.scala 
# scala -classpath . Timer.class 
error: IO error while decoding /root/work_scala/Timer.class with UTF-8
Please try specifying another one using the -encoding option

TODO:エンコーディング周りでエラー。あとで調べる。
→解決 .classが付いていたw

# scala -classpath . Timer
time flies like an arrow...
time flies like an arrow...
time flies like an arrow...
time flies like an arrow...
time flies like an arrow...
time flies like an arrow...
time flies like an arrow...
time flies like an arrow...
^C
  • 無名関数
# cat << _EOD_ > NoNameFunc.scala
object TimerAnonymous {
  def oncePerSecond(callback: () => Unit) {
    while (true) { callback(); Thread sleep 1000 }
  }
  def main(args: Array[String]) {
    oncePerSecond(() =>
      println("time flies like an arrow..."))
  }
}
_EOD_
# scalac NoNameFunc.scala 
# scala -classpath . TimerAnonymous
time flies like an arrow...
time flies like an arrow...
time flies like an arrow...
time flies like an arrow...
time flies like an arrow...
^C

今日はここまで！

追記！

  • クラス
# cat Klass.scala 
class Complex(real: Double, imaginary: Double) {
  def re() = real
  def im() = imaginary
}

object ComplexNumbers {
  def main(args: Array[String]) {
    val c = new Complex(1.2, 3.4)
    println("real part: " + c.re())
    println("imaginary part: " + c.im())
  }
}
# scalac Klass.scala 
# scala ComplexNumbers
real part: 1.2
imaginary part: 3.4
  • 引数なしメソッド
# cat NoArgMethod.scala 
class Complex(real: Double, imaginary: Double) {
  def re = real
  def im = imaginary
}

object ComplexNumbers {
  def main(args: Array[String]) {
    val c = new Complex(1.2, 3.4)
    println("real part: " + c.re)
    println("imaginary part: " + c.im)
  }
}
# scalac NoArgMethod.scala 
# scala ComplexNumbers
real part: 1.2
imaginary part: 3.4
  • 継承とオーバーライド
# cat Inheritance.scala 
class Complex(real: Double, imaginary: Double) {
  def re = real
  def im = imaginary
  override def toString() =
    "" + re + (if (im < 0) "-" else "+") + im + "i"
}

object ComplexNumbers {
  def main(args: Array[String]) {
    val c = new Complex(1.2, 3.4)
    println("toString: " + c.toString())
  }
}
# scalac Inheritance.scala 
# scala ComplexNumbers
toString: 1.2+3.4i

今日はここまで！