Question

I’m just starting out in Scala. I find myself using tuple variables a lot.

For example, here’s some code I wrote:

/* Count each letter of a string and return in a list sorted by character
 * countLetter("test") = List(('e',1),('s',1),('t',2))
*/
def countLetters(s: String): List[(Char, Int)] = {
  val charsListMap = s.toList.groupBy((c:Char) => c)
  charsListMap.map(x => (x._1, x._2.length)).toList.sortBy(_._1)
}

Is this tuple syntax (x._1, x._2 etc) frowned upon by Scala developers?

Answer 1

Are the tuple accessors frowned upon by Scala developers?

Short answer: no.

Slightly longer (by one character) answer: yes.

Too many _n‘s can be a code smell, and in your case the following is much clearer, in my opinion:

def countLetters(s: String): List[(Char, Int)] =
  s.groupBy(identity).mapValues(_.length).toList.sortBy(_._1)

There are lots of methods like mapValues that are specifically designed to cut down on the need for the noisy tuple accessors, so if you find yourself writing _1, etc., a lot, that probably means you’re missing some nice library methods. But occasionally they’re the cleanest way to write something (e.g., the final _1 in my rewrite).

One other thing to note is that excessive use of tuple accessors should be treated as a nudge toward promoting your tuples to case classes. Consider the following:

val name = ("Travis", "Brown")

println("Hello, " + name._1)

As opposed to:

case class Name(first: String, last: String)

val name = Name("Travis", "Brown")

println("Hello, " + name.first)

The extra case class definition in the second version buys a lot of readability for a single line of code.