scala-2.9

问题 The ':javap' command in the scala 2.9.1 console need the tools.jar (from JDK6) in the 'classpath'. From cmd-line it could be done with '-cp' argument or CLASSPATH environment variable. How to do the same for scala console that invoked from SBT with the 'console' and 'console-quick' commands? 回答1: Long answer, that might help you elsewhere. If I want to know about something in SBT, I inspect it: > inspect console [info] Task: Unit [info] Description: [info] Starts the Scala interpreter with

问题 The ':javap' command in the scala 2.9.1 console need the tools.jar (from JDK6) in the 'classpath'. From cmd-line it could be done with '-cp' argument or CLASSPATH environment variable. How to do the same for scala console that invoked from SBT with the 'console' and 'console-quick' commands? 回答1: Long answer, that might help you elsewhere. If I want to know about something in SBT, I inspect it: > inspect console [info] Task: Unit [info] Description: [info] Starts the Scala interpreter with

问题 This question is heavily related to my other question (and may lead to me solving that one) but is definetely different. how to allow passing in a => AnyRef function and call that function I have been playing with different function creations and I am frankly having trouble creating an anonymous function of type => AnyRef and => String. I can create a function of type () => AnyRef and () => String I think. Example 1 I have the following code def debugLazyTest2(msg: => String) : Unit = {

问题 Given the following scala code: var short: Short = 0 short += 1 // error: type mismatch short += short // error: type mismatch short += 1.toByte // error: type mismatch I don't questioning the underlying typing - it's clear that "Short + value == Int". My questions are: 1. Is there any way at all that the operator can be used? 2. If not, then why is the operator available for use on Short & Byte? [And by extension *=, |= &=, etc.] 回答1: The problem seems to be that "+(Short)" on Short class is

问题 Given the following scala code: var short: Short = 0 short += 1 // error: type mismatch short += short // error: type mismatch short += 1.toByte // error: type mismatch I don't questioning the underlying typing - it's clear that "Short + value == Int". My questions are: 1. Is there any way at all that the operator can be used? 2. If not, then why is the operator available for use on Short & Byte? [And by extension *=, |= &=, etc.] 回答1: The problem seems to be that "+(Short)" on Short class is

问题 When I migrated to Scala 2.9.0 from 2.8.1, all of the code was functional except for the Hadoop mappers. Because I had some wrapper objects in the way, I distilled down to the following example: import org.apache.hadoop.mapreduce.{Mapper, Job} object MyJob { def main(args:Array[String]) { val job = new Job(new Configuration()) job.setMapperClass(classOf[MyMapper]) } } class MyMapper extends Mapper[LongWritable,Text,Text,Text] { override def map(key: LongWritable, value: Text, context: Mapper

问题 When I migrated to Scala 2.9.0 from 2.8.1, all of the code was functional except for the Hadoop mappers. Because I had some wrapper objects in the way, I distilled down to the following example: import org.apache.hadoop.mapreduce.{Mapper, Job} object MyJob { def main(args:Array[String]) { val job = new Job(new Configuration()) job.setMapperClass(classOf[MyMapper]) } } class MyMapper extends Mapper[LongWritable,Text,Text,Text] { override def map(key: LongWritable, value: Text, context: Mapper

问题 I'm writing a BloomFilter and wanted to use Scala's default MurmurHash3 implementation: scala.util.MurmurHash3. My compile is failing however with the following compile error: [error] /mnt/hgfs/dr/sandbox/dr-commons/src/main/scala/dr/commons/collection/BloomFilter.scala:214: MurmurHash3 is not a member of scala.util [error] import scala.util.{MurmurHash3 => MH} I'm using Scala 2.9.1 and sbt 0.11.2. Is the MurmurHash3 class not in the 2.9.1 library by default? I assume it is since it's used a

问题 Is it possible to create an AOP like interceptor using Scalas new Dynamic Type feature? For example: Would it be possible to create a generic stopwatch interceptor that could be mixed in with arbitrary types to profile my code? Or would I still have to use AspectJ? 回答1: I'm pretty sure Dynamic is only used when the object you're selecting on doesn't already have what you're selecting: From the nightly scaladoc: Instances x of this trait allow calls x.meth(args) for arbitrary method names meth

问题 after I learned that case classes extend Product, I wondered why they do not extend ProductN. E.g., given a code like: case class Foo(a: Int) I'd expect Foo(1).asInstanceOf[Product1[Int]] to work, but it does not (checked with Scala 2.9.1, and confirmed by other sources and by Product documentation). I was interested in this, because I wanted to declare classes such as: abstract class UnaryOp[T1 <: Exp[_], R](t1: T1) extends Exp[R] { this: Product1[T1] => } This way, a node for a Unary