parboiled-fold-left.scala

class AddingParser(val input: ParserInput) extends Parser {
  def num = rule {
    capture(oneOrMore(CharPredicate.Digit)) ~> (_.toInt)
  }

  def root = rule {
    push(0) ~ zeroOrMore(num ~> ((_: Int) + _)).separatedBy(" ") ~ EOI
  }
}

class XyzTest extends FlatSpec with Matchers {
  "A parser" should "foldLeft" in {
    val ret1 = new AddingParser("").root.run()
    val ret2 = new AddingParser("1 2 3").root.run()
    val ret3 = new AddingParser("x").root.run()

    ret1 should be(Success(0))
    ret2 should be(Success(6))
    ret3 should be('failure)
  }
}