Kotlin elegant way to mutate List<Triple<String, String, String> to Triple<List<String>, List<String>, List<String>>

user_1916413 0
Viewed 1093

I'd like, as succinctly (yet clearly) as possible to transform a List<Triple<String, String, String> to a Triple<List<String>, List<String>, List<String>>.

For instance, say the method performing the transformation is called turnOver, I'd expect:

val matches = listOf(
  Triple("a", "1", "foo"),
  Triple("b", "2", "bar"),
  Triple("c", "3", "baz"),
  Triple("d", "4", "qux")
)
val expected = Triple(
  listOf("a", "b", "c", "d"),
  listOf("1", "2", "3", "4"),
  listOf("foo", "bar", "baz", "qux")
)
matches.turnOver() == expected // true

How to write a succinct, clear, and possibly functional turnOver function?

It's ok to use Arrow-Kt, I already got it as project dependency.

arrow-kt kotlin monad-transformers monads functional-programming
2 Answers
fun turnOver(matches: List<Triple<String, String, String>>) = Triple(
   matches.map { it.first },
   matches.map { it.second },
   matches.map { it.third },
)

would be one obvious solution I reckon.

user_8049670

To the best of my knowledge, there is no way in kotlin stdlib to create a Pair or a Triple out of an iterable, array, or sequence. I believe this is deliberate. So I guess the one above is the clearest possible solution.

user_128129440
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