Scala: convert each digit in a string to an integer

Question

I want to convert each digit in a number to an int. Here is my code

for (in <- lines) { 
    for (c <- in) {
        val ci = c.toInt
        if (ci == 0) {
            // do stuff
        }
    }
}

The result I get is the ascii code, i.e. a 1 gives 49. I'm looking for the value 1. The answer is trivial, I know. I'm trying to pull myself up with my own bootstraps until my Scala course begins in two weeks. Any assistance gratefully accepted.

Can you please give an example input, i.e. "1234" should return the number, 1234? — Kevin Meredith
– Kevin Meredith, Commented Oct 7, 2016 at 15:22
Thanks Kevin, I solved the problem. asDigit was what I was looking for. I wanted 1234 to become 1 and 2 and 3 and 4 so I could process each digit separately. I was getting 49, 50, 51, etc. It would have been easy enough to subtract ascii zero but I felt that would be a poor start to my budding Scala career if I stooped that low. — Fred
– Fred, Commented Oct 7, 2016 at 15:27
How should negative numbers be handled? In other words, what's the output of -1234? — Kevin Meredith
– Kevin Meredith, Commented Oct 7, 2016 at 15:35
For my problem there was no need to handle anything but digits, so the solution is adequate. I'm using Alvin Alexander's Scala Cookbook as a guide. For your question I can use Integer.parseInt("-1234", 10) (assuming base 10). Thanks for asking. — Fred
– Fred, Commented Oct 9, 2016 at 17:29

Mitchell Schwitzer · Accepted Answer · 2016-10-07 08:10:46Z

1

One possible solution is:

for(in <- lines) {
    in.toString.map(_.asDigit).foreach { i =>
        if(i == 1) {
            //do stuff
        }
    }
}

And more compact w/ output:

lines.foreach(in => in.toString.map(_.asDigit).filter(_ == 1).foreach(i => println(s"found $i in $in.")))

If lines is already a collection of Strings, omit the .toString on in.toString.

answered Oct 7, 2016 at 8:10

Mitchell Schwitzer

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1 Comment

Fred Over a year ago

asDigit is the answer. Many thanks. I found the question has been asked before: stackoverflow.com/questions/16241923/… I didn't see it because I searched for string and not char.

Leo Bufi Barrameda · Accepted Answer · 2016-10-07 07:54:14Z

1

You can have this:

val number = 123456
//convert Int to String and do transformation for each character to Digit(Int)
val digitsAsList = number.toString.map(_.asDigit)

This will result to digitizing the number. Then with that Collection, you can do anything from filtering, mapping, zipping: you can checkout the the List api on this page: http://www.scala-lang.org/api/2.11.8/#scala.collection.immutable.List

Hope that's help.

answered Oct 7, 2016 at 7:54

Leo Bufi Barrameda

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