[R] R and pointer

[Prof Brian Ripley]

On Fri, 29 Aug 2003, Laetitia Marisa wrote:

> I want to write a function that modify directly variables passed as 
> parameters (the equivalent in C language of  *ptr/&ptr) so that I don't 
> have to return a list and to reaffect all my variables.
> Is it possible to do so in R?

Yes, with the .Call/.External interface (and there are examples in the ts 
package).  To a limited extent it is possible with .C(DUP=FALSE), but you 
really don't want to go there.

I would want a very good understanding of R's copying semantics before 
doing this (and those are liable to change, too).

-- 
Brian D. Ripley,                  ripley at 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