Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
Ackermann is being studied for recursion. It is quite complex to do TCO for Ackermann. However, there have been some implementation of Ackermann in Haskell with TCO
/*
http://blog.aunndroid.com/2011/11/learning-scala-recursion-and-tco-1.html
Ackermann is being studied for recursion. It is quite complex to do TCO for Ackermann.
However, there have been some implementation of Ackermann in Haskell with TCO
http://lambda-the-ultimate.org/node/2673
*/
object Ackermann {
def main(args : Array[String]) : Unit = {
println(args.toList);
if (args.isEmpty) { printUsage(); return }
val numberStrList = args.toList.foldLeft(List[String]()) {
(iList, str) =>
iList :+ str.foldLeft("") {
case (str, ch) if (ch.isDigit) => str + ch
case (str, ch) => str
}
}
val numberList = numberStrList.foldLeft(List[Int]()) {
(l, str) => l :+ str.toInt
}.take(2)
println(numberList)
if (numberList.length < 2) printUsage()
else {
val result = ackerMann(numberList.head, numberList.last)
printResult((numberList.head, numberList.last), result)
}
}
def ackerMann(m : BigInt, n : BigInt) : BigInt = {
if (m == 0) return n + 1
if (m > 0 && n == 0) return ackerMann(m - 1, 1)
ackerMann(m - 1, ackerMann(m, n - 1))
}
def printUsage() = {
val m = 3
val n = 2
println("Usage is:")
println("scala AckerMann.scala " + m + " " + n)
val result = ackerMann(m, n)
printResult((m, n), result)
}
def printResult(in : (Int, Int), r : BigInt) = {
println("Ackermann value for " + in + " is : " + r)
}
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.
You signed in with another tab or window. Reload to refresh your session. You signed out in another tab or window. Reload to refresh your session.