[Rcpp-devel] Rcpp & static variables

Dirk Eddelbuettel edd at debian.org
Fri Apr 30 19:14:04 CEST 2010

Hi Guiseppe,

Thanks for reposting here!

On 30 April 2010 at 16:07, Giuseppe Milicia wrote:
| Guys,
| I posted this on R-help and Dirk kindly pointed out that this list is a much better place for this sort of questions...
| I was wondering whether anyone experimented with Rcpp and static
| variables. I remember reading that Rcpp is essentially stateless. That
| makes sense. However I just run a piece of code that contains a static STL
| structure, surprisingly  it seems that those static variables are
| preserved... 

I have not used it explicitly.  

But I do use code in production that instantiates singletons etc to keep
e.g. connection handles to a backend.  I initialize this on package load --
using a nice clean hook provided by R and then hold on to it until the
package unloads, which in practice is when the R session ends.  That works
cleanly via constructor and deconstructor calls.
| The question is, can we use static variable to reliably preserve state
| between Rcpp calls? If this is the case, this should be a better way to
| store state than by passing state variables between R and C++. 

I don't see why not. Can you mock up an example of what you are trying to do?

  Regards, Dirk

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