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iOS Swift Closures Functions as First Class Citizens Higher Order Functions

scott harris
PLUS
scott harris
Courses Plus Student 23,789 Points
Posted by scott harris
scott harris
Courses Plus Student 23,789 Points

why do these things never work!!!

I know this is right and have tested it in a playground.. wasting hours.. please fix this

/** 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(mathOp: (Int, Int) -> Int, a: Int, b: Int) -> (Int) { return mathOp(a, b) }

let difference = mathOperation(differenceBetweenNumbers, 10, 20)

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

let difference = mathOperation(differenceBetweenNumbers, 10, 20)
Martin Wildfeuer
Martin Wildfeuer
Courses Plus Student 11,071 Points
Martin Wildfeuer
Martin Wildfeuer
Courses Plus Student 11,071 Points

Same here. It would be nice to know why the code above is not considered correct. Here is my code, just for the records. It is (basically) the same as @scottharris4

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

let difference = mathOperation(differenceBetweenNumbers, 10, 8)
Martin Wildfeuer
Martin Wildfeuer
Courses Plus Student 11,071 Points
Martin Wildfeuer
Martin Wildfeuer
Courses Plus Student 11,071 Points

I think in this particular case it is just the code check. Others had the same problems, although the code works as expected in playground. It seems that removing the parenthesis from the mathOperation return type does the trick. Change your code from

-> (Int)

to

-> Int

So again, it wasn't a mistake you made ;)

1 Answer

scott harris
PLUS
scott harris
Courses Plus Student 23,789 Points
scott harris
scott harris
Courses Plus Student 23,789 Points

Martin Wildfeuer Your the man!! thanks.. i tried so many nonsense things.. i guess i didn't try that... thanks again!!