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kotlinlang

Hello, everyone!  I'm excited to share a new article - if you've ever wondered about when to use _sequences_ and when to use _collections_, this one's for you!
<https://typealias.com/guides/when-to-use-sequences/>

Raise your hand if you follow the "share first, read later" strategy when it comes to this blog. Every post is better than the previous.

My new goal in life is to be able to explain difficult technical concepts with as much clarity as Dave Leeds does.

Great article. What's the "fantastic coroutine-based generator that puts the flow control into the generator function" that the article refers to?

Thanks for the kind words, <@U0QKQ7H3R> and <@U3E6P7LPN>!

<@U0B8QLC2Z> I should probably add a little more information to that spot. Meanwhile, you can find the official Kotlin sample for it here: <https://github.com/JetBrains/kotlin/blob/1b889c976a7f21fdf000ecd1506643ac0a33eca3/libraries/stdlib/samples/test/samples/collections/sequences.kt#L112-L125>

<@U0E9C04JE> really enjoyed this article, I do have one question about the `toList()` performance hit though.

Would providing a `capacity` for `toList` offset that performance hit? This is a crude example but something like this is possible today:

`listOf&lt;String&gt;().asSequence().map { it }.sorted().toCollection(ArrayList(20))`

So adding `toList(defaultCapacity: Int)` could clean it up a bit more. Just thinking for cases where the list size isn’t changing it’d be worth it just tell it what size it should be

Hey <@UFX608MK7> - thanks for asking!

Yes, supplying the initial capacity yourself does help to mitigate the performance hit that you would otherwise get from using just `Sequence.toList()`. Naturally, you'd still want to take it in context with all of the other factors in play, but if you do know the size, your approach would help tip the scales back toward sequences. :thumbsup:

Gotcha, we have some situations where we are mostly just transforming objects so I think in those cases it would help. As soon as you apply a filter or something then all bets are off. Thanks, and again really great article :slightly_smiling_face: