如何将文本输入的字符串转换为Scala中的函数 [英] How to convert a string from a text input into a function in a Scala

问题描述

我正在使用Scala创建一个GUI，它应该根据算法播放一个信号，但是会放入textField中，例如。 SIN（2 * PI * 400 * T）。播放功能完美运行，但问题在于GUI的输入。 textField接受函数并将其转换为字符串，现在我想知道是否有一种简单的方法将字符串转换回函数。我正在考虑将输入与各种有效函数进行匹配，但是我不想限制可能的函数，因为我希望用户能够更多地创建

我仍然斯卡拉相对较新，希望你们中的一个有更好的主意。这里是我到目前为止的代码，它的基本设置侧重于功能。

 对象PlayApp扩展SimpleGUIApplication {
 def top = new MainFrame {
 title =Play Function App
 val label = new Label（输入要播放的函数）
 
对象函数扩展TextField = 10）
 val label2 =新标签（输入播放时间的长度）
对象时间扩展TextField {columns = 10} 
 val按钮=新建按钮（播放） 
 
 content = new BoxPanel（Orientation.Vertical）{
 contents + = label 
 contents + = Function 
 contents + = label2 
 contents + = Time 
 contents + = button 
 border = Swing.EmptyBorder（50，50，20，50）
} 
 
 var f =sin（t）
 
 
 
 $ b ListenTo（Function，Time，button）
 reactions + = {
 case EditDone（Function）=> 
 f = Function.text.toString 
 case EditDone（Time）=> 
 x = Time.text.toInt 
 case ButtonClicked（b）=> 
 play（t => f.toDouble，0，x）
} 
} 
} 
  

解决方案

您希望编译用户输入的代码行，并带有一些有用的前导码。

我没有这样做，所以我没有代码片段（但是尝试搜索），但是可以嵌入REPL，让它编译代码行，然后提取结果。

这是一个使用ILoop获得某些输出的代码片段，但您希望使用IMain来获取包含用户函数的结果类的结果。

  import scala.tools.nsc.interpreter.ILoop 
 import java.io.StringReader 
 import java.io.StringWriter 
 import java.io.PrintWriter 
 import java.io.BufferedReader 
 import scala.tools.nsc.Settings 
 
 object FuncRunner extends App {
 
 val line =sin（2 * Pi * 400 * t）
 
 val lines =import scala.math._ 
 | var t = 1。stripMargin 
 
 val in = new StringReader（lines +\\\
+ line +\\\
val f =（t：Int）=> + line）
 val out = new StringWriter 
 
 val settings = new Settings 
 $ b $ val valoper = new ILoop（new BufferedReader（in），new PrintWriter ））
 val res = looper进程设置
控制台println s[$ res] $ out
} 
  

I am creating a GUI using Scala which should play a signal dependent on the algorithm but into the textField, eg. sin(2*Pi*400*t). The playing function works perfectly, however the issue is the input for the GUI. The textField takes the function and converts it to a string, now I was wondering is there a simple way to convert the string back into a function. I was considering matching the input to various valid functions, however I don't want to restrict the possible functions, as I want the user to be more create

I am still relatively new to Scala, hopefully one of you have a better idea. Here is the code I have so far, its a basic setup focusing on functionality.

object PlayApp extends SimpleGUIApplication {
  def top = new MainFrame {
    title = "Play Function App"
    val label = new Label("Type in function to be played")

    object Function extends TextField ( columns = 10)
    val label2 = new Label("Type in length of time to play")
    object Time extends TextField { columns = 10}  
    val button = new Button("Play")

    contents = new BoxPanel(Orientation.Vertical) {
      contents += label
      contents += Function
      contents += label2
      contents += Time
      contents += button
      border = Swing.EmptyBorder(50, 50, 20, 50)
    }

    var f = "sin(t)"
    var x = 0

    listenTo(Function, Time, button) 
    reactions += {
      case EditDone(Function) =>
        f = Function.text.toString
      case EditDone(Time)     =>
        x = Time.text.toInt
      case ButtonClicked(b)   =>
        play(t => f.toDouble,0,x)
    }
  }
}

解决方案

You want to compile the line of code that the user enters, with some useful preamble.

I haven't done this so I don't have a snippet handy (but try searching), but you can embed the REPL, have it compile the line of code, and then extract the result.

Here is a snippet that uses ILoop to get some output, but you want to use IMain to get a result with the result class that wraps the user function.

import scala.tools.nsc.interpreter.ILoop
import java.io.StringReader
import java.io.StringWriter
import java.io.PrintWriter
import java.io.BufferedReader
import scala.tools.nsc.Settings

object FuncRunner extends App {

  val line = "sin(2 * Pi * 400 * t)"

  val lines = """import scala.math._
    |var t = 1""".stripMargin

  val in = new StringReader(lines + "\n" + line + "\nval f = (t: Int) => " + line)
  val out = new StringWriter

  val settings = new Settings

  val looper = new ILoop(new BufferedReader(in), new PrintWriter(out))
  val res = looper process settings
  Console println s"[$res] $out"
}

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