小编Tom*_*tah的帖子

假设我有一个 bash 数组

X=("a" "b c" "-d" "k j", "-f")

我想是否与开始过滤"-"，并得到 ("a" "b c" "k j")和("-d" "-f")分别。

我怎样才能做到这一点？

当我保存一个方法并稍后返回时，我所有的变量名都变成了 temp，我的所有参数都变成了 arg 并且代码缩进被更改了。关于如何解决这个问题的任何想法？

I'm a new Kotlin Programmer. I tried to change the app icon by deleting the ic_launcher.png files and replacing my own images. As i see that is ridiculous what i'm trying to do, i copied the "Main Activity.kt" and "main_activity.xml" files and created a new project. As i tried to copy the files into the new project, the program throws a lot of errors:

It didn't imported the "kotlinx" packet and didn't perceive the elements in the xml file. As …

拥有这些部门：

libraryDependencies ++= Seq(
  "com.typesafe.akka" %% "akka-http-spray-json" % akkaHttpVersion,
  "com.typesafe.akka" %% "akka-stream" % akkaVersion,
  "com.typesafe.akka" %% "akka-http" % akkaHttpVersion,
  "com.typesafe.akka" %% "akka-actor-typed" % akkaVersion,
  "com.typesafe.akka" %% "akka-stream" % akkaVersion,
  "com.lightbend.akka" %% "akka-stream-alpakka-json-streaming" % akkaJsonStreaming,
  "io.circe" %% "circe-generic-extras" % circeVersion,
  "de.heikoseeberger" %% "akka-http-circe" % akkaHttpCirce,
  "commons-codec" % "commons-codec" % commonsCodecVersion,
  "org.scalatest" %% "scalatest" % scalaTestVersion % "it, test",
)

当我运行时sbt assembly出现错误：

[error] (assembly) deduplicate: different file contents found in the following:
[error] /home/baku/.cache/coursier/v1/https/repo1.maven.org/maven2/com/fasterxml/jackson/core/jackson-annotations/2.10.5/jackson-annotations-2.10.5.jar:module-info.class
[error] /home/baku/.cache/coursier/v1/https/repo1.maven.org/maven2/com/fasterxml/jackson/core/jackson-core/2.10.5/jackson-core-2.10.5.jar:module-info.class
[error] /home/baku/.cache/coursier/v1/https/repo1.maven.org/maven2/com/fasterxml/jackson/core/jackson-databind/2.10.5/jackson-databind-2.10.5.jar:module-info.class

知道如何解决这个问题吗？

我已经开始在 Coursera 上学习 Scala 并且有一些关于squareRootGuess实现的问题如下

我正在尝试实施标准来过滤sqrtGuess定义中的准确猜测，如下所示，但它给了我堆栈溢出错误。

def sqrtGuess(x: Double): Stream[Double] = { 
  def nextGuess(guess: Double): Double = (guess + x / guess)/2

  def isSufficient(guess: Double): Boolean = math.abs(x - guess*guess)/x < 0.001

  def guesses: Stream[Double] = 
    1 #:: guesses.map(nextGuess).filter(isSufficient)

  guesses
}

但是，如果我们在外部定义 isSufficientsqrtGuess并应用于sqrtGuess流，效果会很好。

def sqrtGuess(x: Double): Stream[Double] = { 
    def nextGuess(guess: Double): Double = (guess + x / guess)/2
    def guesses: Stream[Double] = 
        1 #:: guesses.map(nextGuess)
    guesses
}

def isSufficient(guess: Double, x: …

我是 Scala 的新手，我正在尝试 PartialFunctions，这是测试功能的正确方法吗，因为一些教程遵循此方法工作，但对我不起作用？

代码：

object MyScalaApp extends App {
def try29{
    val r = new PartialFunction[Int, Int]  
    { 
        def isDefinedAt(q: Int) = q < 0 // Applying isDefinedAt method  
        def apply(q: Int) = 12 * q // Applying apply method 
    }        
    val rr = new PartialFunction[Double, Double]  
    { 
        def isDefinedAt(q: Double) = {q < 0}
        def apply(q: Double) = 12 * q 
    }

    println(r(1))
    println(r(2))        
    println(rr(-1))
    println(rr(-2))
  }
  }
  try29
}

输出：

12
24
-12.0
-24.0

为什么apply在不匹配第一个条件时会被调用？ …

我是 Scala/函数式编程的新手，想了解我的以下解决方案是否适合函数式编程世界。如果有人可以建议我更好的方法，我将不胜感激。

问题陈述：打印一个列表的每一项，n次

解决方案：

import scala.collection.mutable.ListBuffer

object ListReplication extends App {


  def printNTimes(items: List[Int], n: Int): ListBuffer[Int] = {

    var outputList = new ListBuffer[Int]

    def storeNTime(item: Int): Unit = {

      for (_ <- 1 to n) outputList += item

    }

    for (item <- items) storeNTime(item)

    outputList
  }

  val result = printNTimes(items = List(1,2,4), n = 3)
  println(result)
}