dynamic array output by .C

Greetings,

I am building a stochastic simulation model in a C++ shared library
for R. My model will generate a random number of new observations and
also delete some old observations, however, the numbers cannot be
predicted before the computation engine runs. For simplicity, I am
trying to control my programming at the second stage (pure C++ for R).
It seems .C accepts fixed size of arrays as input (also ouput), can I
modify size of array for deleting old and adding new observations in
.C?

On Thu, 14 Apr 2005, Tib wrote:

Greetings,

I am building a stochastic simulation model in a C++ shared library
for R. My model will generate a random number of new observations and
also delete some old observations, however, the numbers cannot be
predicted before the computation engine runs. For simplicity, I am
trying to control my programming at the second stage (pure C++ for R).
It seems .C accepts fixed size of arrays as input (also ouput), can I
modify size of array for deleting old and adding new observations in
.C?

No, but .Call can.

--
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

from the examples of Writing R Extensions,  I see one still has to
declare the size of arrays by NEW_NUMERIC(n) or
allocVector(REALSXP,n), how can I extend arrays?

from the examples of Writing R Extensions,  I see one still has to
declare the size of arrays by NEW_NUMERIC(n) or
allocVector(REALSXP,n), how can I extend arrays?

I know this question is a little specific, but it would be a lot
helpful if anyone can give me a  quick question. Thanks

On 4/14/05, Prof Brian Ripley <ripley@stats.ox.ac.uk> wrote:

On Thu, 14 Apr 2005, Tib wrote:

Greetings,

I am building a stochastic simulation model in a C++ shared library
for R. My model will generate a random number of new observations and
also delete some old observations, however, the numbers cannot be
predicted before the computation engine runs. For simplicity, I am
trying to control my programming at the second stage (pure C++ for R).
It seems .C accepts fixed size of arrays as input (also ouput), can I
modify size of array for deleting old and adding new observations in
.C?

No, but .Call can.

On Apr 14, 2005, at 6:01 PM, Tib wrote:

from the examples of Writing R Extensions,  I see one still has to
declare the size of arrays by NEW_NUMERIC(n) or
allocVector(REALSXP,n), how can I extend arrays?

AFAIR you cannot extend vectors - it's like in C, you cannot extend allocated 
memory without changing the pointer (i.g.). In order to get a vector of a 
different size, you have to allocate a new one and copy the common contents. 
If you are concerned about efficiency, why don't you just use arbitrary large 
vectors and pass along the number of used elements? Then you can easily add 
elements without re-allocating and just return the number of elements used 
after the operation. That way you can control the probability of having to 
allocate a new vector, possibly making it zero.