Conveniently access next element in collection

CollectionType+Next

extension CollectionType where Index: Comparable {
    subscript(safe index: Index) -> Generator.Element? {
        guard index >= startIndex && index < endIndex else {
            return nil
        }
        
        return self[index]
    }
    
}

extension CollectionType where Generator.Element: Equatable, Index: Comparable {
    subscript(next element: Generator.Element) -> Generator.Element? {
        guard let index = self.indexOf(element) else { return nil }
        return self[safe: index.advancedBy(1)]
    }
}