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riobard/factorial.scala

Created March 21, 2010 23:50
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Scala 2.8 generic Numeric type
Raw
factorial.scala
// Generic factorial function
// require Scala 2.8
def factorial[T](n: T)(implicit m: Numeric[T]): T = {
import m._
if (n == zero) one else n * factorial(n-one)
// this is not tail-optimized
// StackOverFlow for n > 26,800 BigInt on my JVM (1.6 OS X)
}
Raw
factorial_tail.scala
// Generic factorial function (tail optimized)
// require Scala 2.8
def factorial_tail[T](n: T)(implicit m: Numeric[T]): T = {
import m._
def loop(n: T, acc: T): T = if (n <= zero) acc else loop (n - one, acc * n)
loop(n, one)
}
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