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scala - 在 REPL 中除以零时省略了哪些 28 帧？

问题描述

scala> 5 / 0
java.lang.ArithmeticException: / by zero
  ... 28 elided

为一个简单的算术表达式省略了 28 帧？！这些框架是什么，为什么 Scala 需要这么多框架来进行安全除法，为什么一开始就省略了它们？

标签： scalaread-eval-print-loopdivide-by-zero

解决方案

scala> import scala.util.Try
import scala.util.Try

scala> Try(5/0)
res2: scala.util.Try[Int] = Failure(java.lang.ArithmeticException: / by zero)

scala> res2.recover { case e: ArithmeticException => e.printStackTrace }
java.lang.ArithmeticException: / by zero
    at $line8.$read$$iw$$iw$$anonfun$1.apply$mcI$sp(<console>:13)
    at $line8.$read$$iw$$iw$$anonfun$1.apply(<console>:13)
    at $line8.$read$$iw$$iw$$anonfun$1.apply(<console>:13)
    at scala.util.Try$.apply(Try.scala:192)
    at $line8.$read$$iw$$iw$.<init>(<console>:13)
    at $line8.$read$$iw$$iw$.<clinit>(<console>)
    at $line8.$eval$.$print$lzycompute(<console>:7)
    at $line8.$eval$.$print(<console>:6)
    at $line8.$eval.$print(<console>)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at scala.tools.nsc.interpreter.IMain$ReadEvalPrint.call(IMain.scala:786)
    at scala.tools.nsc.interpreter.IMain$Request.loadAndRun(IMain.scala:1047)
    at scala.tools.nsc.interpreter.IMain$WrappedRequest$$anonfun$loadAndRunReq$1.apply(IMain.scala:638)
    at scala.tools.nsc.interpreter.IMain$WrappedRequest$$anonfun$loadAndRunReq$1.apply(IMain.scala:637)
    at scala.reflect.internal.util.ScalaClassLoader$class.asContext(ScalaClassLoader.scala:31)
    at scala.reflect.internal.util.AbstractFileClassLoader.asContext(AbstractFileClassLoader.scala:19)
    at scala.tools.nsc.interpreter.IMain$WrappedRequest.loadAndRunReq(IMain.scala:637)
    at scala.tools.nsc.interpreter.IMain.interpret(IMain.scala:569)
    at scala.tools.nsc.interpreter.IMain.interpret(IMain.scala:565)
    at scala.tools.nsc.interpreter.ILoop.interpretStartingWith(ILoop.scala:807)
    at scala.tools.nsc.interpreter.ILoop.command(ILoop.scala:681)
    at scala.tools.nsc.interpreter.ILoop.processLine(ILoop.scala:395)
    at scala.tools.nsc.interpreter.ILoop.loop(ILoop.scala:415)
    at scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply$mcZ$sp(ILoop.scala:923)
    at scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply(ILoop.scala:909)
    at scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply(ILoop.scala:909)
    at scala.reflect.internal.util.ScalaClassLoader$.savingContextLoader(ScalaClassLoader.scala:97)
    at scala.tools.nsc.interpreter.ILoop.process(ILoop.scala:909)
    at scala.tools.nsc.MainGenericRunner.runTarget$1(MainGenericRunner.scala:74)
    at scala.tools.nsc.MainGenericRunner.run$1(MainGenericRunner.scala:87)
    at scala.tools.nsc.MainGenericRunner.process(MainGenericRunner.scala:98)
    at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:103)
    at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)
res3: scala.util.Try[AnyVal] = Success(())

省略的行基本上是 REPL 读取一行、将其编译成一个类和构造该类的实例的开销，这是对 REPL 中编写的代码进行评估的地方。

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