enumerateWithIndex.swift

extension CollectionType {
    /// Return a lazy SequenceType containing pairs *(i, x)*, 
    /// where *i*s are the sequential indices and *x*s are the elements of `base`.
    func enumerateWithIndex() -> AnySequence<(Index, Generator.Element)> {
        var index = startIndex
        return AnySequence {
            return anyGenerator {
                guard index != self.endIndex else { return nil }
                return (index, self[index++])
            }
        }
    }
}

let str = "Hello from Nate"

// omg
let name = str.characters[str.characters.startIndex.advancedBy(11) ..< str.characters.startIndex.advancedBy(15)]

for (index, char) in name.enumerate() {
    // type doesn't match:
    // error: cannot subscript a value of type 'String.CharacterView' with an index of type 'Int'
    // print(char, name[index])
}

for (index, char) in name.enumerateWithIndex() {
    print(char, name[index])
}
// N N
// a a
// t t
// e e