String+Subscript.swift

extension String {
    subscript (i: Int) -> Character {
        return self[self.startIndex.advancedBy(i)]
    }


    subscript (i: Int) -> String {
        return String(self[i] as Character)
    }


    subscript (r: Range<Int>) -> String {
        let start = startIndex.advancedBy(r.startIndex)
        let end = start.advancedBy(r.endIndex - r.startIndex)

        return self[Range(start ..< end)]
    }
}