Using regex in Scala to group and pattern match

Question

I need to process phone numbers using regex and group them by (country code) (area code) (number). The input format:

country code: between 1-3 digits , area code: between 1-3 digits , number: between 4-10 digits

Examples:

1 877 2638277
91-011-23413627

And then I need to print out the groups like this:

CC=91,AC=011,Number=23413627

This is what I have so far:

String s = readLine
val pattern = """([0-9]{1,3})[ -]([0-9]{1,3})[ -]([0-9]{4,10})""".r
val ret = pattern.findAllIn(s)
println("CC=" + ret.group(1) + "AC=" + ret.group(2) + "Number=" + ret.group(3));

The compiler said "empty iterator." I also tried:

val (cc,ac,n) = s

and that didn't work either. How to fix this?

It's a bad idea to do this splitting. For example, in the UK, area codes can be 5 digits - and UK websites never ask for a separate area code any more, it's completely pointless. — Robin Green
– Robin Green, Commented Nov 23, 2013 at 17:12
This is just the input format of the test program. I just want to know why the regex pattern returns an "empty iterator" or why val(cc,ac,n) = s doesn't work. A working solution would also help. — user3025403
– user3025403, Commented Nov 23, 2013 at 17:14

Akos Krivachy · Accepted Answer · 2015-05-06 16:56:14Z

30

The problem is with your pattern. I would recommend using some tool like RegexPal to test them. Put the pattern in the first text box and your provided examples in the second one. It will highlight the matched parts.

You added spaces between your groups and [ -] separators, and it was expecting spaces there. The correct pattern is:

val pattern = """([0-9]{1,3})[ -]([0-9]{1,3})[ -]([0-9]{4,10})""".r

Also if you want to explicitly get groups then you want to get a Match returned. For an example the findFirstMatchIn function returns the first optional Match or the findAllMatchIn returns a list of matches:

val allMatches = pattern.findAllMatchIn(s)
allMatches.foreach { m =>
  println("CC=" + m.group(1) + "AC=" + m.group(2) + "Number=" + m.group(3))
}

val matched = pattern.findFirstMatchIn(s)
matched match {
  case Some(m) =>
    println("CC=" + m.group(1) + "AC=" + m.group(2) + "Number=" + m.group(3))
  case None =>
    println("There wasn't a match!")
}

I see you also tried extracting the string into variables. You have to use the Regex extractor in the following way:

val Pattern = """([0-9]{1,3})[ -]([0-9]{1,3})[ -]([0-9]{4,10})""".r
val Pattern(cc, ac, n) = s
println(s"CC=${cc}AC=${ac}Number=$n")

And if you want to handle errors:

s match {
  case Pattern(cc, ac, n) =>
    println(s"CC=${cc}AC=${ac}Number=$n")
  case _ =>
    println("No match!")
}

Also you can also take a look at string interpolation to make your strings easier to understand: s"..."

edited May 6, 2015 at 16:56

answered Nov 23, 2013 at 17:25

Akos Krivachy

4,96625 silver badges29 bronze badges

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

2 Comments

user3025403 Over a year ago

I added spaces here to make it clearer, but apparently I made it more confusing. In my actual code, I did NOT put spaces before and after [ -] and it still didn't work.

Akos Krivachy Over a year ago

If anyone is wondering why Pattern is uppercase, it's because as per the Scala style guide constants should be uppercase and this regex should be a constant.

Collectives™ on Stack Overflow

Using regex in Scala to group and pattern match

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related