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iOS Swift Closures Functions as First Class Citizens Higher Order Functions

Posted by Thomas Filepp
Thomas Filepp
5,919 Points

Function Types as Parameter Types Challenge not Passing

So I'm a little baffled as to why my challenge answer isn't passing; it's working as intended no matter what I throw at it in a Playground; and it's honestly verbatim of the example on the iOS Swift docs on functions as parameters. I assume it's something simple/silly, but a little lost as to why this wouldn't pass in it's current form. Any thoughts on what I could be missing?

Thanks!

higherOrderFunctions.swift 
/** 
  For this code challenge, let’s define a math operation as a function that 
  carries out some work on two integers and returns an integer as well. An 
  example is the function below, `differenceBetweenNumbers`, which takes two 
  integers and calculates the difference between the numbers. After calculating, 
  it returns the difference.
*/

func differenceBetweenNumbers(a: Int, b:Int) -> (Int) {
  return a - b
}

// Enter your code below
func mathOperation(mathFunction: (Int, Int) -> (Int), a: Int, b: Int) -> Int {
    return mathFunction(a, b)
}

let difference: Int = mathOperation(differenceBetweenNumbers, 14, 2)
Thomas Filepp
Thomas Filepp
5,919 Points

And the explicit typing on the difference constant was a last ditch effort.

1 Answer

Jhoan Arango
Jhoan Arango
14,575 Points
Jhoan Arango
Jhoan Arango
14,575 Points

Hey Thomas, this is my code which I just tried and it passed. Looks similar to yours, in fact Identical, but I don’t know why it won’t work for you.

func differenceBetweenNumbers(a: Int, b:Int) -> (Int) {
  return a - b
}

// Enter your code below
func mathOperation(math: (Int, Int) -> Int, a: Int, b: Int) -> Int {
    return math(a,b)  
}

let difference = mathOperation(differenceBetweenNumbers, 10, 5)
Thomas Filepp
Thomas Filepp
5,919 Points

How weird, Jhoan! You're right, that looks exactly the same! Maybe some whitespace issue?

Thanks for sharing!