Le 10/12/12 17:45, Douglas Bates a écrit :
On Mon, Dec 10, 2012 at 10:38 AM, Romain Francois
<[email protected] <mailto:[email protected]>> wrote:
Le 10/12/12 17:29, Douglas Bates a écrit :
or does it matter?
A[i,j] is wrong, not valid C or C++ code. so there is only one choice.
Indeed. Thanks. Somehow I managed to convince myself that I had used
A[i,j] at some point and the compiler accepted it. Apparently my memory
isn't what it used to be.
That is even worse than that. At least here, the compiler accepts it,
and does something wrong with it:
#include <Rcpp.h>
using namespace Rcpp;
// [[Rcpp::export]]
double fun(NumericMatrix m){
return m[5,0] ;
}
/*** R
fun( diag(4) )
***/
doug.cpp: In function ‘double fun(Rcpp::NumericMatrix)’:
doug.cpp:7: warning: left-hand operand of comma has no effect
> fun(diag(4))
[1] 1
So m[5,0] gets me m[0] ...
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