So I apparently suck at regexes. I'm trying to co...

# random

[Colton Idle]

So I apparently suck at regexes.

I'm trying to come with the simplest regex based alternative (due to a spec out of my control) to substringAfter()

What would the kotlin regex based alternative to substringAfter("abc") be for example?

[eygraber]

I think .*abc(.*) and then get the first group

[eygraber]

This should do it:

val match = Regex(".*abc(.*)").find("<your string here>")
if(match != null && match.groupValues.size >= 2) {
  match.groupValues[1]
}

[Gleb Minaev]

I would use (?<=abc).* for substring after abc. (At least on JVM.)

UPD. It works on JS, as well.

[Klitos Kyriacou]

Using positive lookbehind, as Gleb suggested:

fun String.reinventedSubstringAfter(delimiter: String) =
    "(?<=$delimiter).*".toRegex().find(this)?.value ?: this

(assuming the delimiter doesn't contain any special characters).
You might want to drop the ?: this at the end, if you want it to return null if it doesn't find the substring. I put it in there to make it compatible with the standard substringAfter which returns the original string.

[Colton Idle]

FWIW This was the closest I could get

fun findThing(chars: String, line: String): String? {
    val matcher = Pattern.compile(".*$chars(.*)").matcher(line)
    if (matcher.matches()) {
      return matcher.group(1)
    }
    return null
  }

[Colton Idle]

but let me try the examples you all gave.

Was hoping for a one-liner really, but doesn't seem like it. lol

[Colton Idle]

oh actually @Klitos Kyriacou seems like a decent one liner

[hallvard]

This is a brilliant tool: https://regex101.com/ − but it does lack the ability to say «listen, your regex is OK, but here's a more efficient one (or a more readable one): ---»

[Alejandro Rios]

You're not the only one that suck with regex, in my case I use ChatGPT to generate the regex and test the result using regex101 😅

[Colton Idle]

I feel like I can sometimes get a regex together, but the regex apis always mess me up. It seems like theres so many ways for a regex and matchers. just makes my head hurt.