[Rcpp-devel] Dynamic Wrapping and Recursion with Rcpp - using an R function?

[Tal Galili]

Hi Hadley,
Thank you for your prompt reply!

I understand your point, and am not sure how to proceed without it.

*Motivation*: I'm currently working on my dendextend package (link to
github<https://github.com/talgalili/dendextend>),
and one of the biggest bottlenecks in working with dendrogram objects is
the need to use recursion for various small tasks (using the dendrapply
function).
*Goal*: to be able to make specific dendrapply_Rcpp functions to make some
operations faster.

If you think there is a better way, or that you still think I should not
use it in this way (and generally, how to fix my the code from my previous
post) - please let me know.

With regards,
Tal






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On Fri, Jul 26, 2013 at 6:44 PM, Hadley Wickham <h.wickham at gmail.com> wrote:

> >             // note: The FUN will change the object x itself
> >             // hence - it must be clear to use an object we wish to
> change
> > (it will NOT be copied!)
>
> Why do you want to do that?  It's a generally a bad idea to modify R
> objects in place.
>
> Here's a simple example showing why C level modification of R object
> is particularly dangerous:
>
> library(inline)
> foo <- cfunction(c(x = "SEXP"), '{
>   INTEGER(x)[0] = 0;
>   return R_NilValue;
> }')
>
> x <- 1:10
> y <- x
> foo(x)
>
> # First value is modified as expected
> x
>
> # But y is also modified!
> y
>
> Hadley
>
> --
> Chief Scientist, RStudio
> http://had.co.nz/
>
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