Swift5 - Dynamically callable types.Swift

import Foundation

@dynamicCallable
class DynamicCalculator {
    func dynamicallyCall(withArguments args: [Int]) -> Int {
        return args.reduce(0, +)
    }
    
    func dynamicallyCall(withKeywordArguments args: KeyValuePairs<String, Int>) -> Int {
        let sum = args.reduce(0) {
            if $1.key == "plus" {
                return $0 + $1.value
            } else if $1.key == "minus" {
                return $0 - $1.value
            } else {
                return $0
            }
        }
        return sum
    }
}

let dynamicCal = DynamicCalculator()
dynamicCal(1, 2, 3) // 1 + 2 + 3 = 6
dynamicCal(minus: 9, plus: 2, 3) // -9 + 2 + 0 (because last argument "3" don't have "key" so it will be ignored (else case))