fixed-point.scala

/** Fixed point combinator: The essence of recursion */
def fix[T, R](f: (T => R) => (T => R)): (T => R) = new Function1[T, R] {
  def apply(t: T): R = f(this)(t)
}

/** Factorial definition with fixed point */
def factorial(recursive: Long => Long) = (x: Long) => x match {
  case 1 => 1
  case x => x * recursive(x-1)
}

/*

Welcome to Scala version 2.8.0.final (Java HotSpot(TM) Server VM, Java 1.6.0_17).
Type in expressions to have them evaluated.
Type :help for more information.

scala> fix(factorial)(3)
res0: Long = 6

*/