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

Amazed by Scala

Top stock of 2008 is GOOG closing at price 307,650000 among (AAPL, GOOG, IBM, MSFT). Amazed by simplicity, clarity and beauty of the following code in Scala from this book.

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

import scala.actors._
import Actor._

val symbols = List( "AAPL", "GOOG", "IBM", "MSFT")
val receiver = self
val year = 2008

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
  }
 }
}