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iOS Swift Closures Functions as First Class Citizens Higher Order Functions

David Frenkel
David Frenkel
14,548 Points

Whats wrong with this? It runs perfectly in Xcode!

Any ideas?

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 (operation: (first: Int, second: Int) -> (Int), firstInt: Int, secondInt: Int ) -> Int {
  return operation(a: firstInt, b: secondInt)
}

edit the ask question button copied in the code mid editing this is the one I wrote and wouldn't compile:

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

// Enter your code below
func mathOperation (mathOperation: (a:Int, b:Int) -> (Int), int1: Int, int2: Int ) -> Int {
    let something = mathOperation(a: int1, b: int2)
    return something
}

print(mathOperation(differenceBetweenNumbers, int1: 6, int2: 5))

2 Answers

Chris Stromberg
PLUS
Chris Stromberg
Courses Plus Student 13,389 Points

I know my code was fine and no it was not the same as mine until you edited it. I was trying to tell you that your code was bad because you were trying to return a parameter named "a" and "b" that did not exist in your function signature.

I'm curious as to why you are naming the parameters of the function that is passed in as a parameter for "mathOperation"? I get it you can do it that way, but the question didn't ask for that.

Your code...

func mathOperation (operation: (first: Int, second: Int) -> (Int)

Why not just submit the code below that does not name the parameters of the function passed in to your function? In addition, the body of your function is suppose to just return the variables passed in, not assign them to a constant that is returned.

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

Or if you want to stick with your naming conventions......

func mathOperation (mathOperation: (Int,Int) -> (Int), int1: Int, int2: Int ) -> Int {
    return mathOperation(int1, int2)
}
Chris Stromberg
PLUS
Chris Stromberg
Courses Plus Student 13,389 Points

Your code below will not compile in Xcode. You are passing two parameters into your return statement named "a" and "b", yet they are no where in your function signature.

func mathOperation (operation: (first: Int, second: Int) -> (Int), firstInt: Int, secondInt: Int ) -> Int {
  return operation(a: firstInt, b: secondInt)
}

This will.

func mathOperation (operation: (first: Int, second: Int) -> (Int), firstInt: Int, secondInt: Int ) -> Int {
    return operation(first: firstInt, second: secondInt)
}

Or you could do a lot less typing and just submit this.

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

And call it.

mathOperationTwo(differenceBetweenNumbers, 5, 2)
David Frenkel
David Frenkel
14,548 Points

Your code is fine, it's same is mine (check edit) but the challenge wont accept it.