ZipArrayCollection.swift

public func zip<A>(_ arrays: [[A]]) -> ZipArrayCollection<A> {
    return ZipArrayCollection(arrays)
}

public struct ZipArrayCollection<A>: Collection {
    
    private let arrays: [[A]]
    
    public let startIndex: Int
    
    public let endIndex: Int
    
    public init(_ arrays: [[A]]) {
        self.arrays = arrays
        self.startIndex = arrays.first?.startIndex ?? 0
        self.endIndex = arrays.first?.endIndex ?? 0
    }
    
    public subscript(position: Int) -> [A] {
        return arrays.map { array in
            return array[position]
        }
    }
    
    public func index(after index: Int) -> Int {
        return index + 1
    }

}