Question

I just want to parse the following string up until the END token then ignore the rest:

val input = """
0)
blah1
blah2
blah3
1)
blah4
blah5
END
blah6
"""

Using

object Pars extends RegexParsers {
  def strings: Parser[List[String]] = rep(str) <~ end
  def str:     Parser[String]       = ".*".r
  def end:     Parser[String]       = "END" <~ rep(".*".r)
}

Pars.parseAll(Pars.strings, input)

goes into an infinite loop and an OutOfMemoryError. What am I doing wrong, and how to fix this?

Answer 1

Just do not use parseAll. Use parse instead.

As for the problem you have, you are saying the same thing twice in a few places:

rep(".*".r)

rep and * both mean “any number of repetitions”. Now, .* matches the empty string, so rep then proceed to match an infinite number of empty strings.

Here’s how I’d rewrite it:

object Pars extends RegexParsers {
  def strings: Parser[List[String]] = 
    ( "END" ^^^ Nil 
    | ".+".r ~ strings ^^ { case head ~ tail => head :: tail }
    )
}