On 20/04/2011 4:38 PM, Dirk Eddelbuettel wrote:
On 20 April 2011 at 16:24, Duncan Murdoch wrote:
| On 20/04/2011 4:06 PM, Sascha Vieweg wrote:
|> Hello R experts
|>
|> I am googling and reading around, however, I can't get it working
|> (perhaps because I do not understand much C, however, I'll give it
|> a try). I am trying to include C++ code into an R routine, where
|> the C++ code looks:
|>
|> #include<iostream>
|> using namespace std;
|> void foo (double* x, double* y, double* out)
|> {
|> out[0] = x[0] + y[0];
|> }
|>
|> Back in R, the command
|>
|> R CMD SHLIB --preclean -o xplusy
|>
|> works fine resulting in two new files, xplusy.o and xplusy.so. The
|> wrapper in R is:
|>
|> dyn.load("xplusy.so")
|> xplusy<- function(x, y){
|> .C("foo", as.double(x), as.double(y), out=double(1))$out
|> }
|> xplusy(1, 2)
|> dyn.unload("xplusy.so")
|>
|> Now, dyn.load() works and xplusy also shows up in getLoadedDLLs().
|> However, when invoking the function, xplusy(1, 2), R complains:
|>
|> Error in .C("foo", as.double(x), as.double(y), out = double(1)): C
|> symbol name "foo" not in load table
|>
|> I found some hints concerning Fortran code producing this error
|> message, but no help concerning C code.
|
| You have C++ code, not C code. C++ normally mangles names of exports.
|
| To get this to work, you should surround your declarations with
|
| extern "C" {
| }
|
| Another possibility is to use the Rcpp package; it writes the interface
| code for you.
I believe Duncan refers to the 'inline' package, rathern than 'Rcpp' (which
itself uses 'inline').
Oops, Dirk is right.
Duncan Murdoch
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