well_actually_this_is_currying.swift

//curries a 2 argument function
func curry<A, B, C>(_ f: @escaping (A, B) -> C) -> (A) -> (B) -> C {
    return { x -> (B) -> C in { y -> C in
            f(x, y)
        }
    }
}

func add(x: Int, y: Int) -> Int {
    return x + y
}

//curry -> take a function that takes 2 (or more) arguments and convert it to a function that takes one argument and returns a function
let adder = curry(add)
// adder is (Int) -> (Int) -> (Int)
//partially apply the add function (in this case providing the left operand)
let add2 = adder(2)
//add2 is (Int) -> Int
let three = add2(1)
//three == 3, if my elementary math serves me correctly