Generic hash value computation for swift objects

hash.swift

func hashValue<T: Hashable>(objects: T?...) -> Int {
    var result = 31
    for object in objects {
        result = (result &* 17) &+ object.hashValue
    }
    return result
}

func hashValue<T: Hashable>(objects: T...) -> Int {
    var result = 31
    for object in objects {
        result = (result &* 17) &+ object.hashValue
    }
    return result
}

extension Optional where Wrapped: Hashable {
    var hashValue: Int {
        switch self {
        case .None: return 0
        case .Some(let object): return object.hashValue
        }
    }
}