import scala.collection.mutable.ArrayBuffer
 
object Main extends App {
  sealed trait Result[+R, +E] {
  	import Result._
  	def flatMap[R1, E1 >: E](f: R => Result[R1, E1]): Result[R1, E1] = this match {
  	  case Err(e) => Err(e)
  	  case Ok(r) => f(r)
  	}
  	def map[R1](f: R => R1) = flatMap(r => Ok(f(r)))
  }
  object Result {
  	final case class Ok[R](r: R) extends Result[R, Nothing]
  	final case class Err[E](e: E) extends Result[Nothing, E]
  }
 
  sealed trait CliError
  object CliError {
  	final case class Io(err: String) extends CliError
  	final case class Parse(err: String) extends CliError
  }
 
  trait File {
  	def read_to_string(ab: ArrayBuffer[Char]): Result[Unit, CliError.Io] = ???
  }
  object File {
  	def open(s: String): Result[File, CliError.Io] = ???
  }
 
  def parse(ab: ArrayBuffer[Char]): Result[Int, CliError.Parse] = ???
 
  def file_double(file_path: String): Result[Int, CliError] = 
    for {
      file <- File.open(file_path)
      contents = ArrayBuffer[Char]()
      _ <- file.read_to_string(contents)
      n <- parse(contents)
    } yield 2 * n
 
  println(file_double("x"))
}

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