String+subscript.swift

import Foundation

public extension StringProtocol {
    
    subscript(offset: Int) -> Character { self[index(startIndex, offsetBy: offset)] }
    
    subscript (bounds: CountableRange<Int>) -> String {
        let start = index(startIndex, offsetBy: bounds.lowerBound)
        let end = index(startIndex, offsetBy: bounds.upperBound)
        return String(self[start..<end])
    }
}