[R-pkg-devel] Call internal R functions in C

[Duncan Murdoch]

On 27/04/2021 12:34 p.m., Cai Li wrote:
> /Dear Duncan, Thank you very much for your helpful advice! In addition, 
> could you kindly help answer my follow-up questions below? /

Sorry, I showed you how I did it.  There are certainly other ways, but 
you'll have to dig around in the manuals to find them.

Duncan Murdoch

> /
> /
> /Instead of passing the private R package environment to C, is there a 
> way to alter the namespace so that files in the "R" directory of the 
> package can be read by the C code but not exported to users? There are 
> specialized export and import functions in the "roxygen2" package that 
> can be used to alter the namespace, and I'm wondering whether altering 
> the namespace would work as well 
> (https://cran.r-project.org/web/packages/roxygen2/vignettes/namespace.html 
> <https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcran.r-project.org%2Fweb%2Fpackages%2Froxygen2%2Fvignettes%2Fnamespace.html&data=04%7C01%7Ccai.li%40yale.edu%7Cfef92ea6326d4803577808d909969553%7Cdd8cbebb21394df8b4114e3e87abeb5c%7C0%7C0%7C637551364617695111%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=PKtQPhcpncRWSzSY5FrYR2Pcbn6LaYDDX0GhEgVtLtA%3D&reserved=0>)./
> /
> /
> /However, if passing the private R package environment to C is the 
> only/best way for the R functions to be read by C without getting 
> exported, could you kindly offer additional advice for how to do this? I 
> can pass an "environment" object from R to C within an SEXP object in C. 
> However, I'm not sure how to pass the "environment" object between C 
> functions. For instance, in the following function, could I declare a 
> "char" object and save the "environment" object as a "char" within the C 
> code?/
> /
> /
> /void
> maketree_diff(int n,
>                int nc,
>                double *y,
>                double **data,
>                int *types,
>                int *ncat,
>                int *treat,
>                struct node *tree,
>                int nmin2,
>                int maxdepth,
>                int method)/
> 
> On Mon, Apr 26, 2021 at 5:30 AM Duncan Murdoch <murdoch.duncan using gmail.com 
> <mailto:murdoch.duncan using gmail.com>> wrote:
> 
>     On 25/04/2021 10:30 p.m., Cai Li wrote:
>      > Thanks Duncan! I was advised not to export those functions in the
>      > namespace and keep them as internals. In terms of this, could you
>     advise
>      > what specific changes should I make to the C code so that I can
>     evaluate
>      > them in a suitable environment? I tried something like
>      > "PROTECT(func_R=lang2(install("Package:::R_function"),
>     func_data))," but
>      > it did not work. Sorry this may be too naive and thanks again.
> 
>     That line creates the expression to evaluate, it doesn't evaluate it.
>     You need to call eval() (the C function) on the result.  Here's some
>     code from rgl that does something similar:
> 
>     R code to initialize:
> 
>     rgl.init <- function(initValue = 0, onlyNULL = FALSE, debug =
>     getOption("rgl.debug", FALSE))
>         .Call( rgl_init,
>           initValue, onlyNULL, environment(rgl.init), debug )
> 
>     The important thing here is "environment(rgl.init)", which is the
>     private environment within the package.
> 
>     Then in C code, save that environment:
> 
>         rglNamespace = in_namespace;
> 
>     and use it later:
> 
>         result = eval(PROTECT(lang2(PROTECT(install("rglFonts")),
> 
>     PROTECT(ScalarString(mkChar(family))))), rglNamespace);
> 
>     Duncan Murdoch
> 
>      >
>      > Cai
>      >
>      > On Sun, Apr 25, 2021 at 8:46 PM Duncan Murdoch
>     <murdoch.duncan using gmail.com <mailto:murdoch.duncan using gmail.com>
>      > <mailto:murdoch.duncan using gmail.com
>     <mailto:murdoch.duncan using gmail.com>>> wrote:
>      >
>      >     On 25/04/2021 7:23 p.m., Cai Li wrote:
>      >      > Hello All,
>      >      >
>      >      > I'm developing a package with C code. My question may be
>     naive: I
>      >     have
>      >      > several internal R functions that need to be called by C,
>     but I
>      >     cannot get
>      >      > it to work or find a solution. It can work if I export
>     those internal
>      >      > functions in namespace, but it fails if I just want to
>     keep them as
>      >      > internal functions without exporting them. I guess I need some
>      >     flags to
>      >      > indicate the "internal" R internal functions? Could you please
>      >     share your
>      >      > thoughts on how to fix this? Much appreciated in advance!
>      >      >
>      >      > //   set up call to R function "R_function"
>      >      >      SEXP func_R;
>      >      >      PROTECT(func_R=lang2(install("R_function"), func_data));
>      >      >
>      >
>      >     It all depends on the environment where you evaluate that
>     expression,
>      >     just as it would if it was R code.  You can't see internal
>     package
>      >     functions from the global environment, you need to evaluate
>     them in the
>      >     package namespace environment.
>      >
>      >     Duncan Murdoch
>      >
>