CODEWITHSUNDEEP
scalamathjvm
nobody
nobody

Reputation: 8263

Scala type error

I'm working on a Hacker Rank problem (https://www.hackerrank.com/challenges/eval-ex) and I got a bit stuck.

I have an exception that keeps coming up:

Solution.scala:12: error: type mismatch;
 found   : (Double, Double) => Double
 required: (AnyVal, AnyVal) => AnyVal
                (1 to 9).reduce((total: Double, current: Double) => Math.pow(exp,current)/factNonRecursive(current))

What am I doing wrong in this Scala code?

Full Code:

object Solution {
def factNonRecursive(num: Double): Double = {
     (1 to (num.toInt)).foldLeft(1) ((a,b) => (a * b)) toDouble
  }
    def main(args: Array[String]) {
        val sc = new java.util.Scanner (System.in);
        var n = sc.nextInt();
        var a0 = 1;
        while(a0 < n){
            var x = sc.nextDouble();
            def e(exp: Double) = {
                (1 to 9).reduce((total: Double, current: Double) => Math.pow(exp,current)/factNonRecursive(current))
            }
            println(e(x))
            a0+=1;
        }
    }
}

Upvotes: 3

Views: 380

Answers (1)

Yuval Itzchakov
Yuval Itzchakov

Reputation: 149538

This happens because you have a Range[Int], which you later call reduce on and it expects an Int, not a Double, hence the compiler is inferring the common ancestor type for both which is AnyVal. You'll need to map the integers to doubles first:

(1 to 9)
  .map(_.toDouble)
  .reduce((_, current) => Math.pow(exp, current) / factNonRecursive(current))

Another approach, instead of Range, would be to use List.range(1.0, 9.0) and avoid the additional map:

List.range(1.0, 9.0)
  .reduce((_, current) => Math.pow(exp, current) / factNonRecursive(current))

Additionally, factNonRecursive can be substituted with product:

(1 to num.toInt).product.toDouble

Upvotes: 4

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