[Rcpp-devel] Default value for Rcpp List

[Romain Francois]

Le 16/08/13 19:33, Dirk Eddelbuettel a écrit :
>
> Hi Romain,
>
> On 16 August 2013 at 19:24, Romain Francois wrote:
> | Le 14/08/13 16:25, Dirk Eddelbuettel a écrit :
> | >
> | >
> | > On 14 August 2013 at 15:57, Matteo Fasiolo wrote:
> | > |  thank you very much for your replies. In the end a named vector is
> | > | enough for my purpose:
> | > |
> | > | cppFunction(
> | > |   '
> | > |   NumericVector myVett(NumericVector x = NumericVector::create(0) )
> | > |  {
> | > |   if(x.size() == 0) x = NumericVector::create(_["a"] = 1.0, _["b"] = 2.0);
> | > |   return x;
> | > |  }
> | > |  '
> | > | )
> | >
> | > You don't even need the assignment in the function definition:
> | >
> | > R> cppFunction("NumericVector matteo(NumericVector x) { if (x.size()==0) x = NumericVector(4); return(x); }")
> | > R> matteo(vector())
> | > [1] 0 0 0 0
> | > R> matteo(1:3)
> | > [1] 1 2 3
> | > R>
> | >
> | > Dirk
> |
> | This might not stay valid code when we put more control for dispatch,
> | argument recognition etc.
> |
> | Some of that is in place with Rcpp::is, the rest will follow. We might
> | lose things like this, but we will gain more useful things instead.
> | And we never said passing 0 arguments to a function needing one works,
> | so it is not a documented feature.
>
> I am missing something here.

It was me who missed something actually. I though you called

matteo()

To my defense, I'm still recovering from an insolation.

> I wrote a function with one argument, I supply one argument in each of the
> two calls -- the argument just happens to be an empty vector precisiely
> because I test for size in the function body.
>
> I don't see anything fishy or questionable here.
>
> Dirk
>


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