小编tux*_*dna的帖子

我有json4s跟随Scala控制台会话,我试图从解析的json中提取String值:

scala> import org.json4s._
import org.json4s._

scala> import org.json4s.native.JsonMethods._
import org.json4s.native.JsonMethods._

scala> val s = """ {"a": "hello"} """
s: String = " {"a": "hello"} "

scala> val json = parse(s)
json: org.json4s.JValue = JObject(List((a,JString(hello))))

scala> json \ "a"
res0: org.json4s.JValue = JString(hello)

scala> res0.extract[String]
<console>:17: error: No org.json4s.Formats found. Try to bring an instance of org.json4s.Formats in scope or use the org.json4s.DefaultFormats.
              res0.extract[String]
                          ^

scala> import org.json4s.Formats._
import org.json4s.Formats._

scala> res0.extract[String]
<console>:20: error: No org.json4s.Formats found. Try to bring …

我看到了一个问题:从数组中创建ArrayList

但是,当我使用以下代码尝试该解决方案时,它并不适用于所有情况:

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;

public class ToArrayList {

    public static void main(String[] args) {
        // this works
        String[] elements = new String[] { "Ryan", "Julie", "Bob" };
        List<String> list = new ArrayList<String>(Arrays.asList(elements));
        System.out.println(list);

        // this works
        List<Integer> intList = null;
        intList = Arrays.asList(3, 5);
        System.out.println(intList);

        int[] intArray = new int[] { 0, 1 };
        // this doesn't work!
        intList = new ArrayList<Integer>(Arrays.asList(intArray));
        System.out.println(intList);
    }
}

我在这做错了什么？代码不应该intList = new ArrayList<Integer>(Arrays.asList(intArray));编译得很好吗？

我可以像这样创建一个sbt项目:

$ mkdir project1
$ cd project1
$ sbt
Loading /usr/share/sbt/bin/sbt-launch-lib.bash

> set name := "project1"
[info] Defining *:name
...

> set scalaVersion :="2.10.2"
[info] Defining *:scalaVersion
...

> set version :="1.0"
[info] Defining *:version
...

> session save
[info] Reapplying settings...

> exit

这build.sbt将为项目创建文件.

$ cat build.sbt 
name := "project1"

scalaVersion :="2.10.2"

version :="1.0"

现在是否有任何命令行来做同样的事情？就像是:

sbt new_project "name" version scala_version

EDIT1

我想出了另一种方式,即创建项目文件夹:

$ mkdir project1
$ cd project1/

更新项目详情:

$ sbt 'set name := "project1"' 'set scalaVersion …

我有这两个错误:

Error:(39, 20) Cannot find an implicit ExecutionContext. You might pass
an (implicit ec: ExecutionContext) parameter to your method
or import scala.concurrent.ExecutionContext.Implicits.global.
    val pipeline = sendReceive

               ^

Error:(39, 20) not enough arguments for method sendReceive: (implicit refFactory: akka.actor.ActorRefFactory, implicit executionContext: scala.concurrent.ExecutionContext, implicit futureTimeout: akka.util.Timeout)spray.client.pipelining.SendReceive.
Unspecified value parameter executionContext.
    val pipeline = sendReceive
               ^

我的代码是:

import scala.util.{Success, Failure}
import scala.concurrent.duration._
import akka.actor.ActorSystem
import akka.pattern.ask
import akka.event.Logging
import akka.io.IO
import spray.can.Http
import spray.client.pipelining._
import spray.util._
import argonaut._, Argonaut._

object test {

case …

我在python中有一个使用tqdm输出进度条的程序，如下所示：

  0%|          |   1/782 [00:02<31:00,  2.38s/it, loss=0.763 ]
 17%|??        | 134/782 [00:19<01:21,  7.98it/s, loss=0.375 ]
100%|??????????| 782/782 [03:50<00:00,  2.73it/s, loss=0.0193]
100%|??????????| 779/782 [03:47<00:00,  4.33it/s, loss=0.0175]
100%|??????????| 780/782 [03:48<00:00,  4.08it/s, loss=0.0172]
100%|??????????| 781/782 [03:48<00:00,  3.83it/s, loss=0.0195]

让我们进入第二行：

 17%|??        | 134/782 [00:19<01:21,  7.98it/s, loss=0.375 ]

字段顺序为：

• 17％：完成百分比。
• |?? | ： 进度条
• 134/782：迭代的项目数超过了项目总数。
• [00:19<01:21, 7.98it/s, loss=0.375 ]：让我们分别在下面进行分解。
  • 00:19<01:21：<<HERE>>无法解决这个问题。
  • 7.98it/s：每秒迭代
  • loss=0.375：正如标签上所说，这是损失。

我知道它显示进度和统计信息，例如每秒迭代，获得的损失等。但是，我无法准确地说出这种时间格式（00:19<01:21例如）在每一行中代表什么？该<标志表示什么？

我正在努力在OSX 10.8上编译PyGLPK.我已经通过自制软件安装了glpk和gmp.我已经验证/ usr/local/include中存在以下文件

gmp.h
gmpxx.h
glpk.h

但我仍然得到以下错误.

python setup.py build
running build
running build_ext
building 'glpk' extension
clang -fno-strict-aliasing -fno-common -dynamic -I/usr/local/include -I/usr/local/opt/sqlite/include -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -I/usr/local/include -Isrc -I/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/include/python2.7 -c src/glpk.c -o build/temp.macosx-10.9-x86_64-2.7/src/glpk.o -m32
clang -fno-strict-aliasing -fno-common -dynamic -I/usr/local/include -I/usr/local/opt/sqlite/include -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -I/usr/local/include -Isrc -I/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/include/python2.7 -c src/lp.c -o build/temp.macosx-10.9-x86_64-2.7/src/lp.o -m32
In file included from src/lp.c:24:
src/kkt.h:30:3: error: unknown type name 'LPXKKT'
  LPXKKT kkt;
  ^
src/lp.c:182:18: warning: implicit declaration of function 'lpx_read_model' is invalid …

在Ruby中我们可以这样做:

$ irb
>> ("aa".."bb").map { |x| x }
=> ["aa", "ab", "ac", "ad", "ae", "af", "ag", "ah", "ai", "aj", "ak", "al", "am", "an", "ao", "ap", "aq", "ar", "as", "at", "au", "av", "aw", "ax", "ay", "az", "ba", "bb"]

在Scala,如果我尝试相同的我得到错误:

$ scala
Welcome to Scala version 2.9.1 (OpenJDK 64-Bit Server VM, Java 1.7.0_51).

scala> ("aa" to "bb").map(x => x)
<console>:8: error: value to is not a member of java.lang.String
              ("aa" to "bb").map(x => x)
                    ^

如何在Scala中获得一系列字符串？

是否有可用于Scala的OAuth2提供程序,我可以使用Scalatra或Play2 Web框架？

我已经看到了这个答案:Scala/Lift的OAuth 2.0提供程序实现

我正在寻找提供程序库而不是OAuth2.0客户端库.

编辑:

我正在寻找Scala OAuth2.0 Provider:http://tuxdna.in/blog/2014/07/09/oauth2-dot-0-server-using-play-2-dot-0-framework-in-斯卡拉/

我有Apache Mesos 0.22.1集群(3个主服务器和5个从服务器),在HA配置和Spark 1.5.1框架中运行Cloudera HDFS(2.5.0-cdh5.3.1).

当我尝试spark-submit编译的HdfsTest.scala示例应用程序(来自Spark 1.5.1源代码)时 - 它java.lang.IllegalArgumentException: java.net.UnknownHostException: hdfs在执行程序日志中失败并出错.只有在我传递HDFS HA Path作为参数hdfs://hdfs/<file>时才会出现此错误,当我通过时hdfs://namenode1.hdfs.mesos:50071/tesfile- 一切正常.

我在启用TRACE日志记录后发现的是Spark驱动程序实际上hdfs://hdfs正确读取了URL,但Spark执行器却没有.

我的Scala应用代码:

import org.apache.spark._
object HdfsTest {
  def main(args: Array[String]) {
    val sparkConf = new SparkConf().setAppName("HdfsTest")
    val sc = new SparkContext(sparkConf)
    val file = sc.textFile(args(0))
    val mapped = file.map(s => s.length).cache()
    for (iter <- 1 to 10) {
      val start = System.currentTimeMillis()
      for (x <- mapped) { x + 2 }
      val end = System.currentTimeMillis()
      println("Iteration " + …

我使用scala版本: Scala code runner version 2.9.2-unknown-unknown -- Copyright 2002-2011, LAMP/EPFL

我在这里尝试深度大小写匹配构造:http://ofps.oreilly.com/titles/9780596155957/RoundingOutTheEssentials.html,代码如下match-deep.scala:

class Role
case object Manager extends Role
case object Developer extends Role

case class Person(name:String, age: Int, role: Role)

val alice = new Person("Alice", 25, Developer)
val bob = new Person("Bob", 32, Manager)
val charlie = new Person("Charlie", 32, Developer)

for( person <- List(alice, bob, charlie) ) {
  person match {
    case (id, p @ Person(_, _, Manager)) => println("%s is overpaid".format(p))
    case …