Emi (Feb 22 2022 at 00:24): Emi (Feb 22 2022 at 00:24):Is there a list of planned language features anywhere? I found the list of planned builtins, but I couldn't find a general list of language features. Are they just tracked through GitHub issues, or is there a place for them?
Brendan Hansknecht (Feb 22 2022 at 00:50):I don't think there is a specific list, but most of the core already exists. I think the biggest known future change is abilities. They were discussed quite a bit in #ideas > Abilities
Emi (Feb 22 2022 at 00:51):alright, thank you!
Emi (Feb 22 2022 at 00:52):im not sure if this warrants making a new topic, but the reason i asked was because i was wondering if any kind of list destructuring is planned for the future?
Brendan Hansknecht (Feb 22 2022 at 00:56):Our lists aren't traditional union based linked list, so it may be more complicated to do something to that nature without faking it due to having a traditional vector style representation. If you have specific thought or ideas, discussion in the #ideas stream would be warranted. Otherwise, if anyone knows specific plans past the builtins currently listed, they will probably pitch in when they read this, but I am pretty sure their are no current plans around list destructuring.
Emi (Feb 22 2022 at 00:59):okay, thank you!
Richard Feldman (Feb 22 2022 at 01:15):yeah I explicitly wanted not to have list destructuring because the x :: xs -> (or first :: rest ->) style would by default have really bad performance (for the reason Brendan mentioned)
Richard Feldman (Feb 22 2022 at 01:16):so I didn't want to encourage a footgun with special syntax! :sweat_smile:
Emi (Feb 22 2022 at 01:21):makes sense!
thanks!
Brendan Hansknecht (Feb 22 2022 at 01:34):I guess we could technically have this with good performance, but it would require a slice type that was able to reference a list with a offset. So (pointer to base list, offset, size). It would need to know about the base list for reference counting reasons.
Richard Feldman (Feb 22 2022 at 01:41):we haven't talked about syntax like [ a, b ] -> though - I could see that being useful, and actually good for performance!
Richard Feldman (Feb 22 2022 at 01:41):like it only matches on that if there are exactly two elements in the list, and names them both
Richard Feldman (Feb 22 2022 at 01:41):that would save a bounds check
Brendan Hansknecht (Feb 22 2022 at 01:43):Makes me think about how in c++ sometimes adding a statement like assert(x.size() >= 5) before using the first 5 elements of a list will make the code faster because it helps the compiler realize it doesn't need to do 5 separate bounds checks.
Richard Feldman (Feb 22 2022 at 01:44):is that all LLVM?
Richard Feldman (Feb 22 2022 at 01:45):like if I did if List.len list > 5 then and then put several List.get and/or List.set calls after the then which all accessed indices between 0 and 4, would LLVM optimize away the bounds checks for me?
Brendan Hansknecht (Feb 22 2022 at 01:55):To my understanding, yes. Of course some of the time it is smart enough to figure it out by itself, but not always.
Richard Feldman (Feb 22 2022 at 02:05):super awesome
Brendan Hansknecht (Feb 22 2022 at 02:11):I just tested this. It 100% works. Adding the if beforehand causes llvm to remove all of the checks and just directly modify the array.
Richard Feldman (Feb 22 2022 at 02:25):niiiice
Richard Feldman (Feb 22 2022 at 02:25):in Roc?
Brendan Hansknecht (Feb 22 2022 at 02:39):Yeah
Brendan Hansknecht (Feb 22 2022 at 02:40):Though not sure what to do in the else branch.
Brendan Hansknecht (Feb 22 2022 at 02:41):In my test just had it return the original list if it was too small
Richard Feldman (Feb 22 2022 at 02:52):the else branch would presumably do whatever any of the failed Results would do
Brendan Hansknecht (Feb 22 2022 at 03:06):With List.set, that would be panic. Which isn't exposed
Richard Feldman (Feb 22 2022 at 03:33):oh List.set doesn't panic on out of bounds, - it returns the same list it was given...so I guess returning the original list in the else branch makes sense in that case! :big_smile:
Brendan Hansknecht (Feb 22 2022 at 03:41):Haha....forgot.
Last updated: Jul 26 2025 at 12:14 UTC