CustomGenericSum.swift

// Custom Protocol
protocol CustomAddable {
static func +(lhs: Self, rhs: Self) -> Self
}
// Sum 2 Numeric elements
func sum<T: CustomAddable>(x: T, y: T) -> T {
return x + y
}
// extending to work with the Custom Protocol
extension Int: CustomAddable {}
extension Double: CustomAddable {}
extension Float: CustomAddable {}
sum(3, 4.5) // result 7.5