 
 public func thongs_strikethrough(color: UIColor, style: NSUnderlineStyle) -> Composer {
     return { attributedString in
-        var s = attributedString.mutableCopy() as! NSMutableAttributedString
+        let s = attributedString.mutableCopy() as! NSMutableAttributedString
         s.addAttribute(NSStrikethroughColorAttributeName, value: color, range: NSMakeRange(0, attributedString.length))
         s.addAttribute(NSStrikethroughStyleAttributeName, value: style.rawValue, range: NSMakeRange(0, attributedString.length))
         return s


public func thongs_underline(color: UIColor, style: NSUnderlineStyle) -> Composer {
    return { attributedString in
        var s = attributedString.mutableCopy() as! NSMutableAttributedString
        s.addAttribute(NSUnderlineColorAttributeName, value: color, range: NSMakeRange(0, attributedString.length))
        s.addAttribute(NSUnderlineStyleAttributeName, value: style.rawValue, range: NSMakeRange(0, attributedString.length))
        return s


public func thongs_concat(comp1: NSAttributedString) -> Composer {
    return { comp2 in
        let s = comp1.mutableCopy() as! NSMutableAttributedString
        s.appendAttributedString(comp2)
        return s
    }
