gistfile1.txt

extension CollectionType where Generator.Element : Equatable {
    func objectNear(object: Self.Generator.Element, indexModifier: Index.Distance) -> Self.Generator.Element? {
        if let index = self.indexOf(object) {
            let limit = indexModifier>0 ? self.indices.endIndex : self.indices.startIndex
            let newIndex = index.advancedBy(indexModifier, limit: limit)
            if self.indices.contains(newIndex) {
                return self[newIndex]
            }
        }
        return nil
    }
}