Using Scala built-in parser combinator to parse basic MIPS code

Question

I am trying to use scala.util.parsing.combinator to parse some MIPS code and my code works for each item (i.e. label, instruction, directive and etc) but it does not work for multiple items/lines. I think the separator regex which I pass to repsep function does not work.

For example, I can parse label str: but I cannot parse str: .asciiz "Hello world!"

  def directive: Parser[Token] = Text.parse ||| Word.parse ||| Data.parse ||| Ascii.parse ||| Asciiz.parse

  def instruction: Parser[Token] = LoadAddress.parse ||| LoadImmediate.parse ||| Move.parse ||| Label.parse

  def misc: Parser[Token] = Label.parse ||| Comment.parse ||| Syscall.parse

  def item: Parser[Token] = directive ||| instruction ||| misc

  // this line I think is the problem ...
  def program: Parser[Seq[Token]] = repsep(item, """[\s\t\n]+""".r) ^^ { _.toList }

  def parseCode(code: Reader[Char]): Seq[Token] = {
    parse(program, code) match {
      case Success(matched, _) => matched
      case Failure(msg, _) => throw new Exception(s"FAILURE: $msg")
      case Error(msg, _) => throw new Exception(s"ERROR: $msg")
    }
  }

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Answer 1

It seems that you're using scala.util.parsing.combinator.RegexParsers and it skips whitespaces by default. You should override it

  override def skipWhitespace = false