Scala example source code file (LoopCommands.scala)

This example Scala source code file (LoopCommands.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

boolean, collection, linecmd, list, loopcommand, loopcommands, none, nullarycmd, result, string, unit

The LoopCommands.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2005-2013 LAMP/EPFL
 * @author  Paul Phillips
 */

package scala
package tools
package nsc
package interpreter

import scala.collection.{ mutable, immutable }
import mutable.ListBuffer
import scala.language.implicitConversions

class ProcessResult(val line: String) {
  import scala.sys.process._
  private val buffer = new ListBuffer[String]

  val builder  = Process(line)
  val logger   = ProcessLogger(buffer += _)
  val exitCode = builder ! logger
  def lines    = buffer.toList

  override def toString = "`%s` (%d lines, exit %d)".format(line, buffer.size, exitCode)
}

trait LoopCommands {
  protected def out: JPrintWriter

  // So outputs can be suppressed.
  def echoCommandMessage(msg: String): Unit = out println msg

  // a single interpreter command
  abstract class LoopCommand(val name: String, val help: String) extends (String => Result) {
    def usage: String = ""
    def usageMsg: String = ":" + name + (
      if (usage == "") "" else " " + usage
    )
    def apply(line: String): Result

    // called if no args are given
    def showUsage(): Result = {
      "usage is " + usageMsg
      Result(keepRunning = true, None)
    }
  }
  object LoopCommand {
    def nullary(name: String, help: String, f: () => Result): LoopCommand =
      new NullaryCmd(name, help, _ => f())

    def cmd(name: String, usage: String, help: String, f: String => Result): LoopCommand =
      if (usage == "") new NullaryCmd(name, help, f)
      else new LineCmd(name, usage, help, f)
  }

  class NullaryCmd(name: String, help: String, f: String => Result) extends LoopCommand(name, help) {
    def apply(line: String): Result = f(line)
  }

  class LineCmd(name: String, argWord: String, help: String, f: String => Result) extends LoopCommand(name, help) {
    override def usage = argWord
    def apply(line: String): Result = f(line)
  }

  class VarArgsCmd(name: String, argWord: String, help: String, f: List[String] => Result)
            extends LoopCommand(name, help) {
    override def usage = argWord
    def apply(line: String): Result = apply(words(line))
    def apply(args: List[String]) = f(args)
  }

  // the result of a single command
  case class Result(keepRunning: Boolean, lineToRecord: Option[String])

  object Result {
    // the default result means "keep running, and don't record that line"
    val default = Result(keepRunning = true, None)

    // most commands do not want to micromanage the Result, but they might want
    // to print something to the console, so we accomodate Unit and String returns.
    implicit def resultFromUnit(x: Unit): Result = default
    implicit def resultFromString(msg: String): Result = {
      echoCommandMessage(msg)
      default
    }
  }
}