[Rcpp-devel] Passing XPtr between functions

[Charles Determan]

Thanks Hadley, much more concise :)

On Wed, Jun 24, 2015 at 2:22 PM, Hadley Wickham <h.wickham at gmail.com> wrote:

> On Wed, Jun 24, 2015 at 11:08 AM, Charles Determan
> <cdetermanjr at gmail.com> wrote:
> > Many thanks Krzysztof, your suggestion works.  I can explicitly create a
> > 'new' arma::mat object and pass the resulting XPtr between functions.  I
> > will work on making everything prettier and document for a submission to
> > Rcpp Gallery unless someone is aware of one that already exists that I
> > somehow overlooked.
> >
> > // [[Rcpp::export]]
> > SEXP testXptr(NumericMatrix A)
> > {
> >     arma::mat *armaMat = new arma::mat(A.begin(),A.rows(), A.cols(),
> false);
> >     XPtr<arma::mat> pMat(armaMat);
> >     return(pMat);
> > }
> >
> > // [[Rcpp::export]]
> > void testReturn(SEXP ptrA, int nr, int nc)
> > {
> >     XPtr<arma::mat> ptrB(ptrA);
> >     arma::mat B = arma::mat( (double *) ptrB->memptr(),
> >           nr,
> >           nc,
> >           false);
> >     B.print("copied matrix");
> > }
>
> You can make this a little nicer:
>
> // [[Rcpp::export]]
> void testReturn(XPtr<arma::mat> ptrA, int nr, int nc)
> {
>     arma::mat B = arma::mat( (double *) ptrA->memptr(),
>           nr,
>           nc,
>           false);
>     B.print("copied matrix");
> }
>
> Hadley
>
> --
> http://had.co.nz/
>
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