How to pass input in scala through command line

Question

  import scala.io._    

  object Sum {    
     def main(args :Array[String]):Unit = {    

      println("Enter some numbers and press ctrl-c")

     val input = Source.fromInputStream(System.in)

     val lines = input.getLines.toList

     println("Sum "+sum(lines))

   }

   def toInt(in:String):Option[Int] =

      try{

        Some(Integer.parseInt(in.trim))

      }

      catch    {
       case e: NumberFormatException => None    
   } 

   def sum(in :Seq[String]) = {

     val ints = in.flatMap(s=>toInt(s))

      ints.foldLeft(0) ((a,b) => a +b)

     } }

I am trying to run this program after passing input I have press ctrl + c but

It gives this message E:\Scala>scala HelloWord.scala Enter some numbers and press ctrl-c 1 2 3 Terminate batch job (Y/N)?

elm · Accepted Answer · 2015-09-04 09:18:44Z

2

Additional observations, note trait App to make an object executable, hence not having to declare a main(...) function, for instance like this,

object Sum extends App {
  import scala.io._
  import scala.util._

  val nums = Source.stdin.getLines.flatMap(v => Try(v.toInt).toOption)
  println(s"Sum: ${nums.sum}")
}

Using Try, non successful conversions from String to Int are turned to None and flattened out.

Also note objects and classes are capitalized, hence instead of object sum by convention we write object Sum.

edited Sep 4, 2015 at 9:18

answered Sep 4, 2015 at 6:55

elm

20.5k15 gold badges72 silver badges116 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

user1668782 Over a year ago

@elm- While I am running the code you have sent is not printing anything

Zee · Accepted Answer · 2015-09-04 13:46:01Z

2

You can also use an external API. I really like scallop API

answered Sep 4, 2015 at 13:46

Zee

1,4303 gold badges20 silver badges42 bronze badges

Comments

Rok Kralj · Accepted Answer · 2015-09-04 06:25:54Z

1

Try this piece of code. It should work as intended.

object Sum {
    def main(args: Array[String]) {
        val lines = io.Source.stdin.getLines
        val numbers = lines.map(_.toInt)
        println(s"Sum: ${numbers.sum}")
    }
}

Plus, the correct shortcut to end the input stream is Ctrl + D.

answered Sep 4, 2015 at 6:25

Rok Kralj

49k10 gold badges75 silver badges80 bronze badges

2 Comments

user1668782 Over a year ago

Thanks its working. I am using in windows 7 So for input stream Ctrl + C is working

user1668782 Over a year ago

-Accepted your answer. Thanks for your help

Collectives™ on Stack Overflow

How to pass input in scala through command line

3 Answers 3

1 Comment

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related