Daily Programmer 206

recurance.scala

//http://www.reddit.com/r/dailyprogrammer/comments/2z68di/20150316_challenge_206_easy_recurrence_relations/
// skip the IO 
val y = "*3 +2 *2"

def f(s: String, x: Int, n: Int): Unit = {
  def rawF(s: String): Int => Int =
    s(0) match {
      case '+' => (x: Int) => x + s(1).toString.toInt
      case '*' => (x: Int) => x * s(1).toString.toInt
      case '/' => (x: Int) => x / s(1).toString.toInt
      case '-' => (x: Int) => x - s(1).toString.toInt
    }

  //convert each string operation to a function
  val funcs =  s.split("\\s").map(rawF(_)).toList
 
  //fold the list of functions, applying them recursivly to the input
  Stream.from(x).map(v => funcs.foldLeft(v){case (acc,f) => f(acc)}).take(n).foreach(println)

}
f(y,1,8)