How to create a parser from Regex in Scala to parse a path?

Question

I am writing a parser in which I am trying to parse a path and do arithmetic calculations. since I cannot use RegexParsers with StandardTokenParsers I am trying to make my own.

Answer 1

There are a couple of mistakes in you regex:

/hdfs://([\d.]+):(\d+)/([\w/]+/(\w+\.w+))

1) There are unnecessary parenthesis (or your forgot a +) - this is not a real mistake but makes it harder to read your regex and fix bugs.

/hdfs://[\d.]+:\d+/[\w/]+/\w+\.w+

2) The last w+ is not escaped:

/hdfs://[\d.]+:\d+/[\w/]+/\w+\.\w+

3) You only allow . but not + for the last part:

/hdfs://[\d.]+:\d+/[\w/]+/\w+([.+]\w+)+

The above expression matches your test case, however, I do suspect, you actually want this expression:

/hdfs://\d+(\.\d+){3}:\d+(/(\w+([-+.*/]\w+)*))+

Answer 2

I solved it writing a trait and using JavaTokenParsers rather than StandardToken Parser.

 trait pathIdentifier extends RegexParsers{

      def pathIdent: Parser[String] ={
          """hdfs://([\d\.]+):(\d+)/([\w/]+/(\w+\.\w+))""".r
    }
}

@Tilo Thanks for your help your solution is working as well but changing extended class to JavaTokenParser helped to solve the problem.