R help - Sep 2015 - how to add 1 + 1 with the interface between R and C

Dear useRs,

I would like some help on how to make the sum of 1 + 1
but using the interface between A and C.

the function call does .call lock and close the R.

Thank you for any help it.

Cleber
#######################
############  R code
text_code <-"
#include <stdlib.h>
#include <R.h>
#include <Rdefines.h>
void testfun( double *k, double *res );
void testfun( double *k, double *res )
{
     res = k + 1;
}
"
sink('test.c')
cat( text_code )
sink()
system("R CMD SHLIB test.c")
dyn.load( "test.dll" )
is.loaded( 'testfun' )
k=1
.C('testfun', k=as.double(k), res=as.double(0) )

####################################
###  Output

 > text_code <-"
+ #include <stdlib.h>
+ #include <R.h>
+ #include <Rdefines.h>
+ void testfun( double *k, double *res );
+ void testfun( double *k, double *res )
+ {
+ res = k + 1;
+ }
+ "
 > sink('test.c')
 > cat( text_code )
 > sink()
 > system("R CMD SHLIB test.c")
cygwin warning:
   MS-DOS style path detected: C:/R/etc/x64/Makeconf
   Preferred POSIX equivalent is: /cygdrive/c/R/etc/x64/Makeconf
   CYGWIN environment variable option "nodosfilewarning" turns off
this
warning.
   Consult the user's guide for more details about POSIX paths:
     http://cygwin.com/cygwin-ug-net/using.html#using-pathnames
gcc -m64 -I"C:/R/include" -DNDEBUG 
-I"d:/RCompile/r-compiling/local/local320/include"     -O2 -Wall  
-std=gnu99 -mtune=core2 -c test.c -o test.o
gcc -m64 -shared -s -static-libgcc -o test.dll tmp.def test.o 
-Ld:/RCompile/r-compiling/local/local320/lib/x64 
-Ld:/RCompile/r-compiling/local/local320/lib -LC:/R/bin/x64 -lR
 >
 > dyn.load( "test.dll" )
 >
 > is.loaded( 'testfun' )
[1] TRUE
 > k=1
 > .C('testfun', k=as.double(k), res=as.double(0) )
$k
[1] 1

$res
[1] 0












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> On 21 Sep 2015, at 04:03 , Cleber N.Borges <klebyn at yahoo.com.br>
wrote:
> 
> Dear useRs,
> 
> I would like some help on how to make the sum of 1 + 1
> but using the interface between A and C.
> 
> the function call does .call lock and close the R.
> 
> Thank you for any help it.
Either you need a basic course in C, or you need a refresher....:

> 
> void testfun( double *k, double *res )
> {
>    res = k + 1;
> }
C is call by value and k and res are pointers. You need a dereferencing step or
nothing with happen. Try

*res = *k + 1;


-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com

peter dalgaard <pdalgd <at> gmail.com>
writes:
> C is call by value and k and res are pointers. You need a dereferencing 
step or nothing with happen. Try
> 
> *res = *k + 1;
Or you use Rcpp which writes the glue code. Save the following into a file:


#include <Rcpp.h>

// [[Rcpp::export]]
int adder(int x, int y) {
  return x + y;
}

/*** R
adder(40, 2)
*/




Running this is as simple as sourcing it:

  R> Rcpp::sourceCpp("/tmp/adder.cpp")

  R> adder(40, 2)
  [1] 42
  R> 

and it even runs the R snippet at the bottom.

Dirk