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/* 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;
}
}
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