gistfile1.scala

def breakIf[T: ClassTag](assertion: => Boolean, args: NamedParam*): Unit =
  if (assertion) break[T](args.toList)

// start a repl, binding supplied args
def break[T: ClassTag](args: List[NamedParam]): Unit = savingContextLoader {
  val msg = if (args.isEmpty) "" else "  Binding " + args.size + " value%s.".format(
    if (args.size == 1) "" else "s"
  )
  echo("Debug repl starting." + msg)
  val repl = new ILoop {
    override def prompt = "\ndebug> "
  }
  repl.settings = new Settings(echo)
  repl.settings.embeddedDefaults[T]
  repl.createInterpreter()
  repl.in = new JLineReader(new JLineCompletion(repl))

  // rebind exit so people don't accidentally call sys.exit by way of predef
  repl.quietRun("""def exit = println("Type :quit to resume program execution.")""")
  args foreach (p => repl.bind(p.name, p.tpe, p.value))
  repl.loop()

  echo("\nDebug repl exiting.")
  repl.closeInterpreter()
}