I think all of my questions are answered. Thank you for your attention and
assistance.
The first question is whether you need to do this. Or, more to the
> point, whether it is safe to do this. In R objects should behave as if
> they are not mutable. Mutation in C code may be OK if the objects are
> not reachable from any R variables, but that almost always means they
> are private to your code so yo can use what you know about internal
> structure.
>
>
Thank you for the warning. I believe it's a legitimate use. In extremely
rough summary: A C function is called via .Call. Inside it, I create the
vector and use SET_*_ELT to populate it. I then return the vector. There is
some amount of complexity between creation and population, and the vector
can potentially be ALTREP.
I don't use SET_*_ELT on any vector I have not created.
COMPLEX0 is not in the API; it will probably be removed from the
> installed header files as we clean these up.
>
My mistake, thank you.
ALTCOMPLEX_SET_ELT is an internal implementation feature and not in the API.
> Again, it will probably be removed from the installed headers.
>
>
Thanks for the warning. I'll make sure to avoid it.
k
On Sat, Jul 3, 2021 at 2:37 AM wrote:
> On Thu, 1 Jul 2021, Konrad Siek wrote:
>
> > Thanks!
> >
> > So what would be the prescribed way of assigning elements to a CPLXSXP
> if I
> > needed to?
>
> The first question is whether you need to do this. Or, more to the
> point, whether it is safe to do this. In R objects should behave as if
> they are not mutable. Mutation in C code may be OK if the objects are
> not reachable from any R variables, but that almost always means they
> are private to your code so yo can use what you know about internal
> structure.
>
> If it is legitimate to mutate you can use SET_COMPLEX_ELT. I've added
> the declaration to Rinternals in R-devel and R-patched.
>
> For SET_COMPLEX_ELT(x, in v) is equivalent to COMPLEX(sexp)[index] = value,
> but that could change in the future it Set methods are supported.
>
> This does materialize a potentially compact object, but again the most
> important question is whether mutation is legitimate at all.
>
> > One way I see is to do what most of the code inside the interpreter does
> and
> > grab the vector's data pointer:
> >
> > COMPLEX(sexp)[index] = value;
> > COMPLEX0(sexp)[index] = value;
> >
>
> COMPLEX0 is not in the API; it will probably be removed from the
> installed header files as we clean these up.
>
> > This will materialize an ALTREP CPLXSXP though, so maybe the best way
> would
> > be to mirror what SET_COMPLEX_ELT does in Rinlinedfuns.h?
> >
> > if (ALTREP(sexp)) ALTCOMPLEX_SET_ELT(sexp, index, value); else
> > COMPLEX0(sexp)[index] = vector;
>
> ALTCOMPLEX_SET_ELT is an internal implementation feature and not in the
> API.
> Again, it will probably be removed from the installed headers.
>
> Best,
>
> luke
>
> > This seems better, but it's not used in the interpreter anywhere as far
> as I
> > can tell, presumably because of the setter interface not being complete,
> as
> > you point out. But should I be avoiding this second approach for some
> > reaosn?
> >
> > k
> >
> > On Tue, Jun 29, 2021 at 4:06 AM wrote:
> > The setter interface for atomic types is not yer implemented. It
> > may
> > be some day.
> >
> > Best,
> >
> > luke
> >
> > On Fri, 25 Jun 2021, Konrad Siek wrote:
> >
> > > Hello,
> > >
> > > I am working on a package that works with various types of R
> > vectors,
> > > implemented in C. My code has a lot of SET_*_ELT operations in
> > it for
> > > various types of vectors, including for CPLXSXPs and RAWSXPs.
> > >
> > > I noticed SET_COMPLEX_ELT and SET_RAW_ELT are defined in
> > Rinlinedfuns.h but
> > > not declared in Rinternals.h, so they cannot be used in
> > packages. I was
> > > going to re-implement them or extern them in my package,
> > however,
> > > interestingly, ALTCOMPLEX_SET_ELT and ALTRAW_SET_ELT are both
> > declared in
> > > Rinternals.h, making me think SET_COMPLEX_ELT and SET_RAW_ELT
> > could be
> > > purposefully obscured. Otherwise it may just be an oversight
> > and I should
> > > bring it to someone's attention anyway.
> > >
> > > I have three questions that I hope R-devel could help me with.
> > >
> > > 1. Is this an oversight, or are SET_COMPLEX_ELT and
> > SET_RAW_ELT not exposed
> > > on purpose? 2. If they are not exposed on purpose, I was
> > wondering why.
> > > 3. More importantly, what would be good ways to set elements
> > of these
> > > vectors while playing nice with ALTREP and avoiding whatever
> > pitfalls
> > > caused these functions to be obscured in the first place?
> > >
> > > Best regards,
> > > Konrad,
> > >
> > > [[alternative
