Any plans for ALTREP lists (VECSXP)?

Thanks for the suggestions, everyone.

Is it not a pressing issue requiring alternatives, since the ?matter_list? object already behaves like a list, and I am just looking for a way to present a native R list (VECSXP) when a regular list is required.

In this case (in my typical use case), the ?matter_list? is homogenous and I use it like a ragged array; however, in general each element could be a different atomic vector type (specifically raw, logical, integer, or double).

Here, as.altrep() is an S4 method for converting my custom ?matter?-class out-of-memory objects into their native R representations using ALTREP.

Seems to work well for the ?matter' vectors, matrices, and arrays, where it just .Call()s my C function for making the corresponding ALTREP object, but the lists were giving me trouble because there I use lapply() to extract and uncompress the ?matter_list? metadata for each list element into a separate S4 ?matter_vec? out-of-memory vector, each of which is then used to create an ALTREP object for the corresponding list element. So it gets costly...

The cost is mostly in re-creating all of the metadata as regular R objects that end up occupying the R_altrep_data1() spot for all of the individual list elements. If I could make an ALTREP list, I could leave the metadata as-is and avoid all of that.

Anyway, not a pressing issue for me either, just something I noticed where having an ALTREP list could be useful, so I was wondering if it was in the plans, which Luke answered.

Thanks,

-Kylie