Replacement of the match using regular expressions in Swift

var data = "Pi = 3.14, exponent = 2.718"
let pattern = "\\d+\\.\\d+"
let regex = try! NSRegularExpression(pattern: pattern, options: .CaseInsensitive)
let range = NSMakeRange(0, data.characters.count)
data = regex.stringByReplacingMatchesInString(data, options: .ReportProgress, range: range, withTemplate: "<f>$0</f>")
//data is "Pi = <f>3.14</f>, exponent = <f>2.718</f>"