Finding X cube + y by using the conventional and Higher-Order Function

[Gokula Krishnan D]

Hello All -

I would like to understand the difference between the Convention way of function and Higher-Order function.

Let me go with an example, X Cube + Y   For the instance my inputs are X= 2 and Y = 5 so the expected result is 13. I'm able to implement the code in both the ways i.e 13

It would be great if you could benefit and advantage of Higher-Order function. And please correct me if my way of implementing the Solution # 2 is not correct.

// Solution # 1

object funXcubeplusY_normal extends App {

  println(sum(cube(2),5))

  def sum(x:Int,y:Int):Int= x+y

  def cube(x:Int):Int= x*x*x

}

Output:

13

//Solution # 2

object funXcubePlusY_HigherOrder extends App {

  println("Sum of 2 Cube plus 5 = " + sum(cube(funXcubePlusY_HigherOrder.fncube,2),5))

  def sum(x:Int,y:Int):Int = x + y

  def cube(m:Int=> Int,n:Int)= m(n)

  def fncube[m](m:Int):Int=  m*m*m
}

Ouput: 

Sum of 2 Cube plus 5 = 13

[Oliver Ruebenacker]

     Hello,

  Your example use a higher-kinded function, but it is not very useful.

  A classical example of a higher-kinded function is a function that finds the zeros (approximately) of another function:

scala> def cutX(x1: Double, x2: Double, f: Double => Double) = { val y1 = f(x1); val y2 = f(x2); (x1*y2 - x2*y1) / (y2 - y1) }
cutX: (x1: Double, x2: Double, f: Double => Double)Double

scala> def zero(f: Double => Double) : Double = { var x1 = 1.0; var x2 = 2.0; while(x1 != x2 && !x1.isNaN && !x1.isInfinite) { val x0 = cutX(x1, x2, f); x2 = x1; x1 = x0 }; x2 }
zero: (f: Double => Double)Double

scala> val f = (x:Double) => x + 10*Math.cos(x)
f: Double => Double = <function1>

scala> val x0 = zero(f)
x0: Double = 1.7463292822528529

scala> f(x0)
res9: Double = -8.881784197001252E-16

     Best, Oliver

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Oliver Ruebenacker

Senior Software Engineer, Diabetes Portal, Broad Institute