On Sat, Apr 26, 2008 at 3:19 AM, Duncan Murdoch <[EMAIL PROTECTED]> wrote: > Ramon Diaz-Uriarte wrote: > > > Dear All, > > > > In a package, I am using ".C" to call some C functions. In one case, > > the number of elements of the return vectors are not known in R before > > the C call. (Two of the vectors are integers, the third is vector of > > character strings). > > > > Passing from R a vector of the maximum possible size would be a huge > > waste. I understand one alternative is to use ".Call", but I'd rather > > avoid it if I can (all of the code seems working except for the return > > of values into R). Another would be to write to a file from C and then > > read that into R, but this looks very ugly. Are there any other > > reasonable alternatives, or should I just use .Call? > > > > > > .Call is usually easiest, but another possibility is to have two entry > points: one to calculate how much space you need, a second to pass in a > vector that's the right size to hold the result. >
You mean making two successive calls to the C code? The problem is that the size of the result is not known until the result is obtained (in my C code, the underlying structure is a linked list that gets stretched as needed as the computation proceeds). So I would not know "where to leave the result from C" in between the two calls to C. Best, R. > Duncan Murdoch > > > Thanks, > > > > R. > > > > > > > > > > > > -- Ramon Diaz-Uriarte Statistical Computing Team Structural Biology and Biocomputing Programme Spanish National Cancer Centre (CNIO) http://ligarto.org/rdiaz ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
