Programmatic Use of Scala REPL

This doc page is specific to features shipped in Scala 2, which have either been removed in Scala 3 or replaced by an alternative. Unless otherwise stated, all the code examples in this page assume you are using Scala 2.

The REPL can be embedded and invoked programmatically.

It supports the javax.script API, or it can be used as either a code interpreter or an interactive command line.

import javax.script._

/** A simple example showing programmatic usage of the REPL. */
object Main extends App {

  // the REPL has some support for javax.script
  val scripter = new ScriptEngineManager().getEngineByName("scala")
  scripter.eval("""println("hello, world")""")

  // compiler settings
  val settings = new Settings
  settings.processArgumentString("-deprecation -feature -Xfatal-warnings -Xlint")

  // the interpreter is used by the javax.script engine
  val intp = new IMain(settings)
  def interpret(code: String): Unit = {
    import Results._
    val res = intp.interpret(code) match {
      case Success => "OK!"
      case _       => "Sorry, try again."
  interpret("""println("hello, world")""")
  interpret("""val who = "world" ; println("hello, $who")""")

  // the REPL uses a line reader and an interpreter interactively
  val interactive = new ILoop()

  // input to the REPL can be provided programmatically
  import{BufferedReader, StringReader, PrintWriter}
  val reader = new BufferedReader(new StringReader(""""hello, world""""))
  val canned = new ILoop(reader, new PrintWriter(Console.out, true))

  // more canning
  val code = """println("hello, world") ; 42"""
  val out =
  println(s"Output is $out")

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