Java regex in a scala parser combinator

Question

Part of my input looks like the following.

Name
John Doe
Sons
Name
Son of John 
28
:
Name
Jane Doe
Daughters
Name
Daughter of Jane 
32
...
...

My parser looks like this

rep("Name" ~> rep("[A-Z ]+[a-z ]+".r)  ~> ("Sons Name" | "Daughters Name") ~> "[0-9]+")

But looks like the regex rep("[A-Z ]+[a-z ]+".r) is also take away Name, Daughter of Jane, Son of John which results in the following error:

failure: `Daughters ' expected but `2' found

Wondering is there is a simple way to fix this ?

Do you want the parser to return the number matched (I assume that's the age of a person) for each person, such that the expected parsed result in the given example would be List(28, 32)? — edi
– edi, Commented Jan 13, 2015 at 22:56
I want the parser to return the Name, Daughter/Son Name and their age. — Soumya Simanta
– Soumya Simanta, Commented Jan 14, 2015 at 3:32

edi · Accepted Answer · 2015-01-14 10:22:30Z

I've reformulated your parser a bit and made some of the regular expressions more explicit. Also, I've set skipWhitespace to false since it lets you have a more fine grained control over pieces being matched. I don't know whether this is most idiomatic approach to tackle your problem, but it works. Hope it helps.

import scala.util.parsing.combinator._

object Parser extends RegexParsers {

  override val skipWhitespace = false

  val word = """[A-Za-z]+""".r
  val separator = """\s+""".r    
  val colon = """(\s+:\s+)?""".r // optional colon
  val ws = """[^\S\n]+""".r      // all whitespace except newline
  val age = "[0-9]+".r

  val name = (repsep(word, ws) <~ separator) ^^ (_.mkString(" "))
  val nameHeader = "Name" ~ separator
  val childNameHeader = ("Daughters" | "Sons") ~ separator ~ nameHeader

  val person = nameHeader ~> name ~ (childNameHeader ~> name) ~ age <~ colon ^^ (p => (p._1._1, p._1._2, p._2))
  val persons = rep(person)

}

object Main extends App {

  val input  =
    """Name
      |John Doe
      |Sons
      |Name
      |Son of John
      |28
      |:
      |Name
      |Jane Doe
      |Daughters
      |Name
      |Daughter of Jane
      |32""".stripMargin

  val result = Parser.parse(Parser.persons, input)
  // prints '[13.3] parsed: List((John Doe,Son of John,28), (Jane Doe,Daughter of Jane,32))'
  println(result)
}

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