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Scala parser combinators never use atEnd and sometimes never terminate #5514

scabug opened this issue Feb 22, 2012 · 1 comment


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commented Feb 22, 2012

Please see code below. It does not terminate even though the expected result is to stop applying rep when reader is depleted.

import scala.util.parsing.combinator.Parsers
import scala.util.parsing.input.Reader
import scala.util.parsing.input.Position

object DemoApp extends App {
	val parsers = new DemoParsers
	val reader = new DemoReader(10)
	val result = parsers.startsWith("s").*(reader)
	Console println result

class DemoReader(n: Int) extends Reader[String] {
	def atEnd = n == 0
	def first = "s" + n
	def rest = new DemoReader(n - 1)
	def pos = new Position { def line = 0; def column = 0; def lineContents = first }

class DemoParsers extends Parsers {
	type Elem = String
	def startsWith(prefix: String) = acceptIf(_ startsWith prefix)("Error: " + _)

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commented Feb 22, 2012

Imported From:
Reporter: Tymur Porkuian (fixpoint)
Affected Versions: 2.9.1

@scabug scabug closed this May 7, 2012

@scabug scabug added the minimized label Apr 7, 2017

@scabug scabug added this to the 2.10.0-M3 milestone Apr 7, 2017

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