[Rcpp-devel] "No matching function for call to as(double&)" error at compile time

[Romain Francois]

Le 06/12/12 05:57, Robert A'gata a écrit :
> Hi,
>
> I am not sure what I am missing. Any help would be greatly appreciated.
> I have the following code:
>
> // myList will have column called "a"
> Rcpp::List myList = someInputList;
> Rcpp::NumericVector test = Rcpp::as<Rcpp::NumericVector>(myList["a"]);
>
> /* up to the above line, everything compiles.
> Now I want to get a double out from first element of test.*/
>
> double test0 = Rcpp::as<double>(test[0]);
>
> It is the above line that the compiler complains about. I have include
> Rcpp.h and also my -I path includes Rcpp/include directory. I am not
> sure why I am getting an error here? Or I have to make a copy of SEXP
> object representing test[0] before passing it into Rcpp::as<double>?
> Thank you.
>
> Best regards,
>
> Robert

Of course you get a compile error. I'm sure it was explicit enough. I get :

foo.cpp:7: error: no matching function for call to ‘as(double&)’

which should give you enough of a clue.


The argument for as is a SEXP :

      template <typename T> T as( SEXP m_sexp)

and NumericVector::operator[](int) gives you a reference to a double

Romain

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