extension Array where Element : Hashable {
    
    func modalValue() -> Self.Element? {
        
        // populate a dictionary of element vs count
        var dict: [Self.Element : Int] = [:]
        self.forEach { v in
            if let count = dict[v] {
                dict[v] = count + 1
            } else {
                dict[v] = 1
            }
        }

        // find the maximum count, and then return the first key that has that count
        if let max = dict.values.max() {
            for kv in dict {
                if kv.value == max {
                    return kv.key
                }
            }
        }
        
        return nil
    }
}