Rcpp integration when C++ functions call each other

Question

I am getting started with the Rcpp framwork for intergrating C++ function with R.

The following integration works just fine:

   cppFunction('
   double normal_dens( double x ) 
   {
     const double  SQRT2PI = 2.50662827463;
     return( exp(-x*x/2.0)/SQRT2PI );
   }
  ')

next I want to integrate:

   cppFunction('
   double test( double x ,double a) 
   {
    return( a* normal_dens(x);); 
   }
  ')

the internal cpp-compiler complains ( rightly-so ) that the function normal_dens is not known. What is the easiest way to do this?

many thx

Answer 1

Each of these cppFunction calls create an independent shared library. They don't know about each other.

An easy alternative is to have all on the same file:

#include <Rcpp.h>

// [[Rcpp::export]]
double normal_dens( double x ) {
  const double  SQRT2PI = 2.50662827463;
  return( exp(-x*x/2.0)/SQRT2PI );
}

// [[Rcpp::export]]
double test( double x ,double a){
  return( a* normal_dens(x);); 
}

and then call sourceCpp on this file. Then later, you'll want to learn how to make packages.