swift3 String.range(of:返回空

Question

如果值中没有小数，"myDRange“语句将返回一个范围。如果有小数，它将返回nil。其他语句按预期返回范围。我做错了什么？

Swift3 - myDRange返回nil

var pseudoXML = "<d>4.0</d><rs>Test</rs><o>0</o>"
let myDRange = pseudoXML.range(of: "(?<=<d>)[^.]+(?=</d>)", options: .regularExpression)
let myRSRange = pseudoXML.range(of: "(?<=<rs>)[^.]+(?=</rs>)", options: .regularExpression)
let myORange = pseudoXML.range(of: "(?<=<o>)[^.]+(?=</o>)", options: .regularExpression)

Swift3 - myDRange返回一个范围

var pseudoXML = "<d>40</d><rs>Test</rs><o>0</o>"
let myDRange = pseudoXML.range(of: "(?<=<d>)[^.]+(?=</d>)", options: .regularExpression)
let myRSRange = pseudoXML.range(of: "(?<=<rs>)[^.]+(?=</rs>)", options: .regularExpression)
let myORange = pseudoXML.range(of: "(?<=<o>)[^.]+(?=</o>)", options: .regularExpression)

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