Convert the order of array and needle

isin.swift

// standard
[1,2,3,4,5,6,7].contains(3)

// alternative
protocol A {
    func `is`(in haystack: [Self]) -> Bool
    func `is`(in haystack: Self...) -> Bool
}

extension A where Self: Comparable {
    func `is`(in haystack: [Self]) -> Bool { return haystack.contains(self) }
    func `is`(in haystack: Self...) -> Bool { return self.is(in: haystack) }
}

extension Int: A {}
3.is(in: [1,2,3,4,5,6,7])
3.is(in: 1,2,3,4,5,6,7)