Curry Function in Swift

Question

I want to make a function that return a curry function like below

func addTwoNumbers(a: Int)(b: Int) -> Int {
    return a + b
}

addTwoNumbers(4)(b: 6) /         


        

Answer 1

I recently found that currying was removed back in Swift3. I created my own version which is repetitive but does the job.

precedencegroup CurryPrecedence {
    associativity: left
    higherThan: MultiplicationPrecedence
}
infix operator <<== :CurryPrecedence
//1 param
func <<==(_ f: @escaping (A) -> (Z), _ p:A) -> () -> (Z)  {
    { f(p) }
}
//2 param
func <<==(_ f: @escaping (A, B) -> (Z), _ p:B) -> (A) -> (Z)  {
    { (A) in f(A,p) }
}
//3 param
func <<==(_ f: @escaping (A, B, C) -> (Z), _ p:C) -> (A, B) -> (Z)  {
    { (A, B) in f(A,B,p) }
}
//4 param
func <<==(_ f: @escaping (A, B, C, D) -> (Z), _ p:D) -> (A, B, C) -> (Z)  {
    { (A, B, C) in f(A,B,C,p) }
}

To use it:

let ten = (addTwoNumbers <<== 6 <<== 4)()

or

let ten = (addTwoNumbers <<== 6)(4)