R devel - Apr 2024 - Is ALTREP "non-API"?

> On Apr 24, 2024, at 12:52 AM, Hadley Wickham <h.wickham at gmail.com>
wrote:
> 
>> 
>> 
>> 
>>>> ALTREP is part of the official R api, as illustrated by the
presence of
>>>> src/include/R_ext/Altrep.h. Everything declared in the header
files in
>> that
>>>> directory is official API AFAIK (and I believe that is more
definitive
>> than
>>>> the manuals).
>>>> 
>>> 
>>> That is not true at all - the presence of header does not
constitute
>> declaration of something as the R API. There are cases where internal
>> functions are in the headers for historical or other reasons since the
>> headers are used both for the internal implementation and packages.
That's
>> why this is in R-exts under "The R API: entry points for C
code":
>>> 
>>> If I understand your point correctly, does this mean that
>> Rf_allocVector() is not part of the "official" R API? It does
not appear to
>> be documented in the "The R API: entry points for C code"
section.
>>> 
>> 
>> It does, obviously:
>> https://cran.r-project.org/doc/manuals/R-exts.html#Allocating-storage-1
> 
> 
> I'm just trying to understand the precise definition of the official
API
> here. So it's any function mentioned in R-exts, regardless of which
section
> it appears in?
> 
> Does this sentence imply that all functions starting with alloc* are part
> of the official API?
> 
Again, I can only quote the R-exts (few lines below the previous "The R
API" quote):


We can classify the entry points as
API
Entry points which are documented in this manual and declared in an installed
header file. These can be used in distributed packages and will only be changed
after deprecation.


It says "in this manual" - I don't see anywhere restriction on a
particular section of the manual, so I really don't see why you would think
that allocation is not part on the API.

Cheers,
Simon



>> For many purposes it is sufficient to allocate R objects and manipulate
> those. There are quite a
>> few allocXxx functions defined in Rinternals.h?you may want to explore
> them.
> 
> Generally, things in a file with "internal" in its name are
internal.
> 
> Hadley
> 
> -- 
> http://hadley.nz
> 
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> 
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>

>
>
>
> >>> That is not true at all - the presence of header does not
constitute
> >> declaration of something as the R API. There are cases where
internal
> >> functions are in the headers for historical or other reasons since
the
> >> headers are used both for the internal implementation and
packages.
> That's
> >> why this is in R-exts under "The R API: entry points for C
code":
> >>>
> >>> If I understand your point correctly, does this mean that
> >> Rf_allocVector() is not part of the "official" R API? It
does not
> appear to
> >> be documented in the "The R API: entry points for C
code" section.
> >>>
> >>
> >> It does, obviously:
> >>
https://cran.r-project.org/doc/manuals/R-exts.html#Allocating-storage-1
> >
> >
> > I'm just trying to understand the precise definition of the
official API
> > here. So it's any function mentioned in R-exts, regardless of
which
> section
> > it appears in?
> >
> > Does this sentence imply that all functions starting with alloc* are
part
> > of the official API?
> >
>
> Again, I can only quote the R-exts (few lines below the previous "The
R
> API" quote):
>
>
> We can classify the entry points as
> API
> Entry points which are documented in this manual and declared in an
> installed header file. These can be used in distributed packages and will
> only be changed after deprecation.
>
>
> It says "in this manual" - I don't see anywhere restriction
on a
> particular section of the manual, so I really don't see why you would
think
> that allocation is not part on the API.
>
Because you mentioned that section explicitly earlier in the thread. This
obviously seems clear to you, but it's not at all clear to me and I suspect
many of the wider community. It's frustrating because we are trying
our best to do what y'all want us to do, but it feels like we keep getting
the rug pulled out from under us with very little notice, and then have to
spend a large amount of time figuring out workarounds. That is at least
feasible for my team since we have multiple talented folks who are paid
full-time to work on R, but it's a huge struggle for most people who are
generally maintaining packages in their spare time.

For the purposes of this discussion could you please "documented in the
manual" means? For example, this line mentions allocXxx functions:
"There
are quite a few allocXxx functions defined in Rinternals.h?you may want to
explore them.". Does that imply that they are documented and free to use?

And in general, I'd urge R Core to make an explicit list of functions that
you consider to be part of the exported API, and then grandfather in
packages that used those functions prior to learning that we weren't
supposed to.

Hadley


-- 
http://hadley.nz

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