Scala example source code file (ackermann.scala)

This example Scala source code file (ackermann.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

ack, ack, array, array, console, int, int, thread, thread

The Scala ackermann.scala source code

/* The Computer Language Shootout 
   http://shootout.alioth.debian.org/
   contributed by Isaac Gouy (Scala novice)
*/

object ackermann {
   def main(args: Array[String]) = {
     val n = toPositiveInt(args);

     // spawn a new thread fixes stack overflows on Windows 1.5 JDK
     // see more on ticket #1508
     val t = new Thread {
       override def run {
	 Console println("Ack(3," + n + "): " + ack(3,n));
       }
     }
     t.start()
     t.join()
   }

   def ack(m: Int, n: Int): Int = 
      if (m == 0) n + 1;
      else if (n == 0) ack(m-1, 1);
      else ack(m-1, ack(m, n-1));

   private def toPositiveInt(s: Array[String]) = {
      val i = 
         try { Integer.parseInt(s(0)); } 
         catch { case _ => 1 }
      if (i>0) i; else 1;
   }
}