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My favorite showcase of Scala to this day is pattern matching on regular expressions: val date = raw"(\d{4})-(\d{2})-(\d{2})".r "2004-01-20" match

My favorite showcase of Scala to this day is pattern matching on regular expressions: val date = raw"(\d{4})-(\d{2})-(\d{2})".r "2004-01-20" match case date(year, month, day) => s"$year was a good year for PLs." This reads better than any equivalent Java or Kotlin code, while being much easier to maintain (e.g. matching against more than one regex).

pantsforbirds 2y ago
Would the kotlin equivalent just be: val dateRegex = Regex("""(\d{4})-(\d{2})-(\d{2})""") val (year, _, _) = dateRegex.matchEntire("2004-01-20")!!.destructured println("$year was a good year for PLs.") ?
- vvillena 2y ago
  The Scala snippet works for all inputs, it's something you would see on a real codebase. It also scopes the regex captures within the match expression. The code also scales better for more complex cases where a string is tested against multiple regexes, or against specific captured values. I assume this Kotlin snippet would, at minimum, need to do null-checking on "matchEntire" before it finds its way to a production codebase.
vaylian 2y ago
What does the .r do at the end of the first line?
- vvillena 2y ago
  It's a method call on a String that returns a Regex type, courtesy of the Scala standard library.
  - vips7L 2y ago
    This is my problem with Scala. Too many fancy things hidden behind text with no meaning. Why the hell is this ‘r’ instead of something with a name that has meaning like toRegex?
    - vvillena 2y ago
      It's a convenience method for a specific case where the result is already obvious, because it's called on a string literal that already looks like a regex. Any competent Scala dev reviewer would reject code that uses the "r" method on a variable. If you want a more verbose option, you can import the Regex type and write: val date = Regex(raw"(\d{4})-(\d{2})-(\d{2})") And of course, explicit type declarations can further document the code.
      - vips7L 2y ago
        > Any competent Scala dev reviewer would reject code that uses the "r" method on a variable. Boy do I have news for you

pantsforbirds 2y ago

Would the kotlin equivalent just be: val dateRegex = Regex("""(\d{4})-(\d{2})-(\d{2})""") val (year, _, _) = dateRegex.matchEntire("2004-01-20")!!.destructured println("$year was a good year for PLs.") ?

vvillena 2y ago
The Scala snippet works for all inputs, it's something you would see on a real codebase. It also scopes the regex captures within the match expression. The code also scales better for more complex cases where a string is tested against multiple regexes, or against specific captured values. I assume this Kotlin snippet would, at minimum, need to do null-checking on "matchEntire" before it finds its way to a production codebase.

vaylian 2y ago

What does the .r do at the end of the first line?

vvillena 2y ago
It's a method call on a String that returns a Regex type, courtesy of the Scala standard library.
- vips7L 2y ago
  This is my problem with Scala. Too many fancy things hidden behind text with no meaning. Why the hell is this ‘r’ instead of something with a name that has meaning like toRegex?
  - vvillena 2y ago
    It's a convenience method for a specific case where the result is already obvious, because it's called on a string literal that already looks like a regex. Any competent Scala dev reviewer would reject code that uses the "r" method on a variable. If you want a more verbose option, you can import the Regex type and write: val date = Regex(raw"(\d{4})-(\d{2})-(\d{2})") And of course, explicit type declarations can further document the code.
    - vips7L 2y ago
      > Any competent Scala dev reviewer would reject code that uses the "r" method on a variable. Boy do I have news for you