## Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community!

### Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

# Swift code on higher order functions is fine in XCode but here says it has problems. Why?

Why my code is not accepted? In the second part, it asks for passing differenceBetweenNumbers into mathOperation with couple of integers and assigning it to a constant "difference". In Xcode it appears fine and without error.

higherOrderFunctions.swift
```/**
For this code challenge, letβ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: (Int, Int) -> (Int), first: Int, second: Int) -> (Int) {
return operation(first, second)
}

let difference = mathOperation(differenceBetweenNumbers, 10, 4)
```

MOD

Here is the answer (you could change the ints):

```let difference = mathOperation(differenceBetweenNumbers, 2, 1)
```

This forum post has an answer that explains it.

Changing ints is irrelevant. The forum post you provided, indicates that extra parenthesis for return types cause the problem. I just tried `func mathOperation( operation: (Int, Int) -> Int, first: Int, second: Int) -> Int` with my current ints and it was okay and the assignment passed.

This is a Treehouse bug. Since it accepts mathOperation with extra parenthesis for the first part of the assignment but for the second, it doesn't and displays an error message which is completely irrelevant to the problem. Needless to say that both ways of writing mathOperation (with or without extra parenthesis) are syntactically valid and XCode has no problem with it. I've reported the bug couple of weeks ago but apparently no one here cares! So...

Hey Alireza Rafiei,

The problem should be fixed now. Our backend was inferring (Int) as a tuple containing an Int. That should match the Xcode result now