R help - Jun 2021 - Embedded R: Test if initialized

Dear R friends,

I am currently trying to write a piece of C code that uses ?embedded R?, and for
specific reasons*, I cannot keep track if R already has been initialized. So the
code snippet looks like this:

LibExtern char *R_TempDir;

if(R_TempDir == NULL)
    ?throw exception R not initialized?

I have seen that the source code of Rf_initialize_R itself checks if it is
ivoked twice (num_initialized), but this latter flag does not seem to
accessible, or is it?

int Rf_initialize_R(int ac, char **av)
{
    int i, ioff = 1, j;
    Rboolean useX11 = TRUE, useTk = FALSE;
    char *p, msg[1024], cmdlines[10000], **avv;
    structRstart rstart;
    Rstart Rp = &rstart;
    Rboolean force_interactive = FALSE;

    if (num_initialized++) {
	fprintf(stderr, "%s", "R is already initialized\n");
	exit(1);
    }


Is the test of the TempDir a good substitute, or should I choose another
solution? Having said this, it may be a good idea to expose a function
Rf_R_initialized that performs such a test.

Thank you for your consideration.

Best regards,

Matthias

*The use case is an R library that connects to swi-prolog and allows the
?embedded? swi-prolog to establish the reverse connection to R. In that case,
i.e., R -> Prolog -> R, I do not want to initialize R a second time.



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I believe this is the wrong list for this post. See the posting guide,
linked below, for one that is more appropriate.

Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Wed, Jun 16, 2021 at 12:51 PM Matthias Gondan <matthias-gondan at
gmx.de>
wrote:
> Dear R friends,
>
> I am currently trying to write a piece of C code that uses ?embedded R?,
> and for specific reasons*, I cannot keep track if R already has been
> initialized. So the code snippet looks like this:
>
> LibExtern char *R_TempDir;
>
> if(R_TempDir == NULL)
>     ?throw exception R not initialized?
>
> I have seen that the source code of Rf_initialize_R itself checks if it is
> ivoked twice (num_initialized), but this latter flag does not seem to
> accessible, or is it?
>
> int Rf_initialize_R(int ac, char **av)
> {
>     int i, ioff = 1, j;
>     Rboolean useX11 = TRUE, useTk = FALSE;
>     char *p, msg[1024], cmdlines[10000], **avv;
>     structRstart rstart;
>     Rstart Rp = &rstart;
>     Rboolean force_interactive = FALSE;
>
>     if (num_initialized++) {
>         fprintf(stderr, "%s", "R is already
initialized\n");
>         exit(1);
>     }
>
>
> Is the test of the TempDir a good substitute, or should I choose another
> solution? Having said this, it may be a good idea to expose a function
> Rf_R_initialized that performs such a test.
>
> Thank you for your consideration.
>
> Best regards,
>
> Matthias
>
> *The use case is an R library that connects to swi-prolog and allows the
> ?embedded? swi-prolog to establish the reverse connection to R. In that
> case, i.e., R -> Prolog -> R, I do not want to initialize R a second
time.
>
>
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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