Jared Cone (Nov 08 2024 at 17:27): Jared Cone (Nov 08 2024 at 17:27):If a closure captures a parameter and that closure is used in-place (not stored somewhere for later use), does it have to create copies of the captures?
doSomething = \model ->
doSomethingElse model.item (\item ->
{model & item})
does this have to copy model?
Brendan Hansknecht (Nov 08 2024 at 20:24):It will copy any non-refcounted captures.
Brendan Hansknecht (Nov 08 2024 at 20:24):For refcounted captures, it will increment the refcount and hold a reference
Jared Cone (Nov 08 2024 at 20:29):How can you know if it's a refcounted capture?
Luke Boswell (Nov 08 2024 at 20:36):simple fixed sized types like i32, f32 or a record or tuple containing only these are not refcounted, while things like Str or List a or records or tuples containing these are
Brendan Hansknecht (Nov 08 2024 at 20:36):Just depends on the data type. Anything on the heap is refcount: Box, Str, List, recursive tag...I think that's it in roc. Everything else is not
Brendan Hansknecht (Nov 08 2024 at 20:37):A record or tuple would be copied, but all of its refcounted fields would just be referenced.
Brendan Hansknecht (Nov 08 2024 at 20:37):So a gigantic record could be problematic.
Jared Cone (Nov 08 2024 at 20:39):So if it's a record it does make a copy, but if the record has a List field, that list points to the same memory as the thing it was copied from. Makes sense thanks!
Brendan Hansknecht (Nov 08 2024 at 20:39):Yep
Last updated: Jul 26 2025 at 12:14 UTC