为什么scalac在某些场景下不能优化尾递归? [英] Why can't scalac optimize tail recursion in certain scenarios?

问题描述

为什么 scalac(Scala 编译器)优化尾递归?

证明这一点的代码和编译器调用:

<前>> 猫 foo.scala类 Foo {def ifak(n: Int, acc: Int):Int = {如果(n == 1)acc否则 ifak(n-1, n*acc)}}> scalac foo.scala> jd-gui Foo.class导入 scala.ScalaObject;公开课 Foo实现 ScalaObject{公共 int ifak(int n, int acc){返回 ((n == 1) ? acc :ifak(n - 1, n * acc));}}

解决方案

可以被覆盖的方法不能是尾递归的.试试这个:

class Foo {private def ifak(n: Int, acc: Int): Int = {如果(n == 1)acc否则 ifak(n-1, n*acc)}}

Why doesn't scalac (the Scala compiler) optimize tail recursion?

Code and compiler invocations that demonstrates this:

> cat foo.scala 
class Foo {
 def ifak(n: Int, acc: Int):Int = {  
   if (n == 1) acc  
   else ifak(n-1, n*acc)  
 }
}

> scalac foo.scala
> jd-gui Foo.class
import scala.ScalaObject;

public class Foo
  implements ScalaObject
{
  public int ifak(int n, int acc)
  {
    return ((n == 1) ? acc : 
      ifak(n - 1, n * acc));
  }
}

解决方案

Methods that can be overridden can NOT be tail recursive. Try this:

class Foo {
  private def ifak(n: Int, acc: Int): Int = {  
    if (n == 1) acc  
    else ifak(n-1, n*acc)  
  }
}

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