CODEWITHSUNDEEP
scala
Azmath Shaik
Azmath Shaik

Reputation: 39

how to calculate factorial of list using higher order function in scala

I am trying to calculate factorial of elements present in a Scala list for suppose List(1,2,3) using Higher order function as in below code

object HigherOrderFunctionEg{
 def main(args :Array[String]){
  val input = args(0).toInt
    val intiList :List[Int] = List.range(1,input+1)
    def factorial(n: Int): Int = {
      if (n == 0) 
      return 1
      else
      return n * factorial(n-1)
     }
    def myHigherOrderFn (factorial : Int => Unit, intiList : List[Int]) : Unit = 
     {
   intiList.foreach(factorial)
    println(intiList.foreach(factorial))
    }
    myHigherOrderFn(factorial, intiList)
 }
}

When I am trying to scala HigherOrderFunctionEg.scala 3 I am getting output as only empty braces () where as I am expecting output like 1 2 6

Upvotes: 2

Views: 1919

Answers (2)

Tim
Tim

Reputation: 27356

There are multiple problems:

  1. factorial is Int => Int but you have used Int => Unit
  2. foreach returns Unit so printing the result will always give ()
  3. myHigherOrderFun returns Unit so it isn't really a function.

This is a better way to write it:

def myHigherOrderFn(factorial: Int => Int, intiList: List[Int]): List[Int] =
  intiList.map(factorial)

myHigherOrderFn(factorial, intiList).foreach(println)

Upvotes: 3

Mahesh Chand
Mahesh Chand

Reputation: 3250

The problem is the return type of factorial is Int => Unit. It should be Int => Int

As it takes an integer and returns an integer.

You need to change your definition like this.

def myHigherOrderFn (factorial : Int => Int, intiList : List[Int]) : Unit =
    intiList.foreach(e => println(factorial(e)))

Upvotes: 1

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