Amazed by Scala #1: objects and compilation

7 minutes and here is an object, that can be compiled into java classes:

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1. import scala.actors._  
2. import Actor._  
3.   
4. object TopStock {  
5.  val symbols = List( "AAPL", "GOOG", "IBM", "MSFT")  
6.  val receiver = self  
7.  val year = 2008  
8.    
9.   def main(args: Array[String]) = {  
10.  symbols.foreach { symbol =>  
11.    actor { receiver ! getYearEndClosing(symbol, year) }  
12.  }  
13.     
14.  val (topStock, highestPrice) = getTopStock(symbols.length)  
15.  printf("Top stock of %d is %s closing at price %f\n", year, topStock, highestPrice)  
16.   }  
17.   
18.  def getYearEndClosing(symbol : String, year : Int) = {  
19.    val url = "http://ichart.finance.yahoo.com/table.csv?s="+   
20.    symbol + "&a=11&b=01&c=" + year + "&d=11&e=31&f=" + year+  
21.              "&g=m"  
22.      
23.    val data = io.Source.fromURL(url).mkString  
24.    val price = data.split("\n")(1).split(",")(4).toDouble  
25.    (symbol, price)  
26.  }  
27.   
28.  def getTopStock(count : Int) : (String, Double) = {  
29.    (1 to count).foldLeft("", 0.0) { (previousHigh, index) =>  
30.   receiveWithin(10000) {  
31.     case (symbol : String, price : Double) =>  
32.    if (price > previousHigh._2) (symbol, price) else previousHigh  
33.   }  
34.    }  
35.  }    
36. }  

import scala.actors._
import Actor._

object TopStock {
 val symbols = List( "AAPL", "GOOG", "IBM", "MSFT")
 val receiver = self
 val year = 2008
 
  def main(args: Array[String]) = {
 symbols.foreach { symbol =>
   actor { receiver ! getYearEndClosing(symbol, year) }
 }
  
 val (topStock, highestPrice) = getTopStock(symbols.length)
 printf("Top stock of %d is %s closing at price %f\n", year, topStock, highestPrice)
  }

 def getYearEndClosing(symbol : String, year : Int) = {
   val url = "http://ichart.finance.yahoo.com/table.csv?s="+ 
   symbol + "&a=11&b=01&c=" + year + "&d=11&e=31&f=" + year+
             "&g=m"
   
   val data = io.Source.fromURL(url).mkString
   val price = data.split("\n")(1).split(",")(4).toDouble
   (symbol, price)
 }

 def getTopStock(count : Int) : (String, Double) = {
   (1 to count).foldLeft("", 0.0) { (previousHigh, index) =>
  receiveWithin(10000) {
    case (symbol : String, price : Double) =>
   if (price > previousHigh._2) (symbol, price) else previousHigh
  }
   }
 }  
}

Saved in TopStock.scala. Compiled with

> scalac TopStock.scala

ran with

> scala TopStock

Top stock of 2008 is GOOG closing at price 307,650000