Either left or right

Scala has an Either[+A, +B] type for us. But before we talk about Either, let's use it. We'll refactor our code with the Either type:

import java.lang.Exception 
import scala.util.{Failure, Success, Try} 
 
object Main extends App { 
 
  def toInt(str: String): Either[String, Int] = Try(str.toInt) match { 
    case Success(value) => Right(value) 
    case Failure(exp) => Left(s"${exp.toString} occurred," + 
      s" You may want to check the string you passed.") 
  } 
 
  println(toInt("121")) 
  println(toInt("-199")) 
  println(toInt("+ -199")) 
} 

The following is the result:

Right(121) 
Right(-199) 
Left(java.lang.NumberFormatException: For input string: "+ -199" occurred, You may want to check the string you passed.) 

In the preceding code, we knew things might go wrong with the conversion from a string to an int. So the result can be either an exception or the intended integer. So we tried to do the same: we used the Either type with the left value as a String...