[Rcpp-devel] Rcpp: Distinguishing between input types to function call

[Romain Francois]

Le 04/12/12 13:05, Christian Gunning a écrit :
> Just curious (and trying to learn the patterns):
> Is this a potential candidate for a functor/templated class,
> particularly if topoSort() was called repeatedly for a particular
> instantiation?
> ...I feel like I almost get this.
>
> thanks,
> -Christian
>
>> and two other functions to instantiate the template:
>>
>> RcppExport SEXP C_topoSort_st ( SEXP XX_ ){
>>       return topoSort< Eigen::Map<Eigen::MatrixXi> >( XX_ ) ;
>> }
>>
>> RcppExport SEXP C_topoSort_sp ( SEXP XX_ ){
>>       return topoSort< Eigen::MappedSparseMatrix<double> >( XX_ ) ;
>> }
>>
>> or Perhaps you would have one instead of the two, something like this:
>>
>> RcppExport SEXP topoSort_facade ( SEXP XX_ ){
>>
>>          if( Rf_inherits( XX_, "dgCMatrix" ) ){
>>                  return topoSort< Eigen::MappedSparseMatrix<double> >( XX_ ) ;
>>          } else {
>>                  return topoSort< Eigen::Map<Eigen::MatrixXi> >( XX_ ) ;
>>          }
>> }

I'm not sure I understand what you mean. I use functors whenever the 
function needs to hold its own data, something close to e.g. lexical 
scoping in R.

The issue here is that what we get from the R side is always a "SEXP", 
so we need to use this if/else code to disambiguate it at runtime and 
then let the template do its job.

Romain


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