On Fri, Dec 6, 2013 at 10:42 AM, Prof Brian Ripley <rip...@stats.ox.ac.uk> wrote: > On 06/12/2013 14:42, Gábor Csárdi wrote: >> >> On Fri, Dec 6, 2013 at 9:38 AM, Duncan Murdoch <murdoch.dun...@gmail.com> >> wrote: >>> >>> On 06/12/2013 8:21 AM, Larissa Hauer wrote: >> >> [...] >>> >>> >>> >>> I would not assume that a 2D matrix in C doesn't have gaps in it between >>> the >>> rows. Let C treat it as a vector, and write a little macro that does the >>> indexing. For example, >>> >>> #define INDEX(i,j) (i) + rows*(j) >> >> >> I would make this >> >> #define INDEX(i,j) ((i) + rows*(j)) >> >> just to be on the safe side. > > > And to be safer on a 64-bit platform > > #define INDEX(i,j) ((i) + rows*(R_xlen_t)(j)) > > since rows*j might overflow there.
Indeed. Of course this still does not save you from indexing out-of-range and integer overflow in the addition. Gabor [...] ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
