R from C — Simplest Possible Helloworld

Question

What is the simplest possible C function for starting the R interpreter, passing in a small expression (eg, 2+2), and getting out the result? I\'m trying to compile with Mi

Answer 1

You want to call R from C?

Look at section 8.1 in the Writing R Extensions manual. You should also look into the "tests" directory (download the source package extract it and you'll have the tests directory). A similar question was previously asked on R-Help and here was the example:

#include  
#include  

SEXP hello() { 
  return mkString("Hello, world!\n"); 
} 

int main(int argc, char **argv) { 
  SEXP x; 
  Rf_initEmbeddedR(argc, argv); 
  x = hello(); 
  return x == NULL;             /* i.e. 0 on success */ 
} 

The simple example from the R manual is like so:

 #include 

 int main(int ac, char **av)
 {
     /* do some setup */
     Rf_initEmbeddedR(argc, argv);
     /* do some more setup */

     /* submit some code to R, which is done interactively via
         run_Rmainloop();

         A possible substitute for a pseudo-console is

         R_ReplDLLinit();
         while(R_ReplDLLdo1() > 0) {
           add user actions here if desired
         }
      */
     Rf_endEmbeddedR(0);
     /* final tidying up after R is shutdown */
     return 0;
 }

Incidentally, you might want to consider using Rinside instead: Dirk provides a nice "hello world" example on the project homepage.

In you're interested in calling C from R, here's my original answer:

This isn't exactly "hello world", but here are some good resources:

• Jay Emerson recently gave a talk on R package development at the New York useR group, and he provided some very nice examples of using C from within R. Have a look at the paper from this discussion on his website, starting on page 9. All the related source code is here: http://www.stat.yale.edu/~jay/Rmeetup/MyToolkitWithC/.
• The course taught at Harvard by Gopi Goswami in 2005: C-C++-R (in Statistics). This includes extensive examples and source code.