[Rcpp-devel] Keep variables in C++ environment

Mattias Nyström Mattias.Nystrom at srh.slu.se
Thu Jan 28 13:44:24 CET 2010

Static variables was a simple and working solution for my problem! Thanks!

-----Original Message-----
From: Dirk Eddelbuettel [mailto:edd at debian.org] 
Sent: den 27 januari 2010 18:10
To: Romain Francois
Cc: Mattias Nyström; rcpp-devel at lists.r-forge.r-project.org
Subject: Re: [Rcpp-devel] Keep variables in C++ environment

On 27 January 2010 at 17:35, Romain Francois wrote:
| On 01/27/2010 05:29 PM, Mattias Nyström wrote:
| > Hi,
| >
| > I'm using the Rcpp package to do some operations in C++. For example reading large files and do some calculations. I call the C++ function several times, so I would like the C++ environment keep the objects and variables in the memory when I'm going back to R. So my question; is it possible to set variables, read in files, etc. in C++ and keep them in the memory until I call the function next time?
| With the new api, i.e. the classes in the Rcpp namespace it is 
| definitely possible. This was one of the goals.
| So if you do something like this :
| Rcpp::CharacterVector x(2) ;
| x[0] = "foo" ;
| x[1] = "bar" ;
| You can then put x wherever you like and use it when you come back.
| With the classic api, it is not possible I think. Dirk might prove me wrong.

Aren't we talking about standard static variables?  

edd at ron:/tmp> cat staticVar.cpp 

#include <iostream>

void foo(void) {
	static int ctr;
	std::cout << "Ctr now " << ++ctr << std::endl;

int main(void) {
edd at ron:/tmp> g++ -o staticVar staticVar.cpp 
edd at ron:/tmp> ./staticVar
Ctr now 1
Ctr now 2
Ctr now 3
edd at ron:/tmp> 

Seems to fit the bill, no?


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