[Rcpp-devel] Method with default params using RCPP_MODULE

[Hao Ye]

>
> In sum, the easiest may be to 'hide' the module and deal with this from
> the R
> side exposing both variants from there and then just calling the one you
> have now.


I agree - though I don't think you even need two variants of the C++
function if there's an R function to handle default arguments.

Best,
--
Hao Ye
hye at ucsd.edu

On Wed, Oct 26, 2016 at 8:53 AM, Dirk Eddelbuettel <edd at debian.org> wrote:

>
> On 26 October 2016 at 09:48, Sergio Bra wrote:
> | I am exposing a c++ class using Rcpp. It works fantastic, but my problem
> is how
> | to implement a method which has default params. I have the class:
> |
> | class myClass {
> |
> |     public:
> |
> |         int myMethod(int param1, int param2 = 0);
> | }
> |
> | and I config the module:
> |
> | RCPP_MODULE(mymodule) {
> |     class_<myClass>("myClass")
> |         .constructor()
> |         .method("myMethod", &myClass::myMethod)
> | ;
> | }
> |
> | When I try to execute the function in R passing only the mandatory param
> I get
> | an error because R does not recognize the function, but if I execute it
> with
> | both params, it works great. So, how can I define the method in order to
> be
> | able to execute it without informing the optional params?
>
> Hm, I have the feeling I am doing that somewhere too.  Did you check
> existing
> packages with modules?
>
> I just glanced at RcppCNPy and it does it, albeit with free functions.
>
> You can definitely have multiple constructors, maybe have one with one int
> (defaulting value two) and one with two ints?   There are subtle
> constraints
> where because of the _C_ interface so you have to 'waste' two function
> names
> on this.
>
> In sum, the easiest may be to 'hide' the module and deal with this from
> the R
> side exposing both variants from there and then just calling the one you
> have now.
>
> Makes sense?
>
> Dirk
>
> --
> http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org
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