print("iOS implementation about closure") let double = { (i: Int) -> Int in return i * 2 } let result = [1,2,3,4].map(double) // [2,4,6,8] print(result) //MARK: https://medium.com/hash-coding/swift-functions-closure-part-i-e339faa51ffc let someFunction: (Int, Int) -> Int = { $0 + $1 }