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# Challenge Task 1 of 1 In the editor, we're using the map function on an array of numbers to perform an operation.

What's wrong with what I've done here? I'm using a trailing closure and short hand syntax to double each value

closures.swift
```func doubleValue(i: Int) -> Int {
return i * 2
}

let doubler = doubleValue
let doubledValues = [1,2,3,4].map() { \$0 * 2 }
```

I'm not sure if it is still useful for you, but you just have to delete the parenthesis from map like this: let doubledValues = [1,2,3,4].map { \$0 * 2 }

This also worked for me:

```let doubledValues = [1,2,3,4]  //.map(doubler)

let doubler = doubledValues.map { \$0 * 2 }
func double(_ i: Int) -> Int {
return i * 2
}

print(doubler)
```

func double(_ i: Int) -> Int { return i * 2 }

let array = [1,2,3,4]

let doubler = array.map { \$0 * 2}