(尾)递归函数的CPS/Continuations StackOverflowError

Question

有没有办法在CPS内有一个尾递归函数而不抛出StackOverflow？

import scala.util.continuations._
object CPSStackOverflow {
  def main(args: Array[String]) = {
    reset {
      def recurse(i: Int): Unit @suspendable = {
        println(i)
        shift { k: (Unit => Unit) =>
          k( () ) // just continue
        }
        recurse(i + 1)
      }
      recurse(1)
    }
  }
}

结果为以下StackOverflowError：

1298
1299
1300
Exception in thread "main" java.lang.StackOverflowError
    at java.nio.CharBuffer.wrap(CharBuffer.java:350)
    at sun.nio.cs.StreamEncoder.implWrite(StreamEncoder.java:246)
    at sun.nio.cs.StreamEncoder.write(StreamEncoder.java:106)
    at java.io.OutputStreamWriter.write(OutputStreamWriter.java:190)
    at java.io.BufferedWriter.flushBuffer(BufferedWriter.java:111)
    at java.io.PrintStream.write(PrintStream.java:476)
    at java.io.PrintStream.print(PrintStream.java:619)
    at java.io.PrintStream.println(PrintStream.java:773)
    at scala.Console$.println(Console.scala:198)
    at scala.Predef$.println(Predef.scala:182)
    at test.CPSStackOverflow$$anonfun$main$1.recurse$1(CPSStackOverflow.scala:9)
    at test.CPSStackOverflow$$anonfun$main$1$$anonfun$recurse$1$2.apply(CPSStackOverflow.scala:13)
    at test.CPSStackOverflow$$anonfun$main$1$$anonfun$recurse$1$2.apply(CPSStackOverflow.scala:10)
    at scala.util.continuations.ControlContext$$anonfun$flatMap$2$$anonfun$apply$2.apply(ControlContext.scala:71)
    at test.CPSStackOverflow$$anonfun$main$1$$anonfun$recurse$1$1.apply(CPSStackOverflow.scala:11)
    at test.CPSStackOverflow$$anonfun$main$1$$anonfun$recurse$1$1.apply(CPSStackOverflow.scala:10)
    at scala.util.continuations.package$$anonfun$shiftR$1.apply(package.scala:58)
    at scala.util.continuations.package$$anonfun$shiftR$1.apply(package.scala:58)
    at scala.util.continuations.ControlContext$$anonfun$flatMap$2.apply(ControlContext.scala:68)
    at scala.util.continuations.ControlContext$$anonfun$flatMap$2.apply(ControlContext.scala:67)
    at scala.util.continuations.ControlContext$$anonfun$flatMap$2$$anonfun$apply$2.apply(ControlContext.scala:73)
    at test.CPSStackOverflow$$anonfun$main$1$$anonfun$recurse$1$1.apply(CPSStackOverflow.scala:11)
    at test.CPSStackOverflow$$anonfun$main$1$$anonfun$recurse$1$1.apply(CPSStackOverflow.scala:10)
    at scala.util.continuations.package$$anonfun$shiftR$1.apply(package.scala:58)
    at scala.util.continuations.package$$anonfun$shiftR$1.apply(package.scala:58)
etc...

有什么方法可以避免这个错误吗？跳床？通过抛出异常来展开堆栈？谢谢!

Answer 1

您正在调用延续中的另一个函数。Scala不支持跨方法尾递归，因为JVM不支持。

Answer 2

您可以使用-Xss2M运行Java，但是这个错误可能只会在一千次迭代之后出现。只要你的方法不是尾递归的，你就无法解决这个问题。