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

3 messages · Robert A'gata, Dirk Eddelbuettel, Romain Francois

Original
Robert A'gata
# 
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
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Dirk Eddelbuettel
#
On 5 December 2012 at 23:57, Robert A'gata wrote:
| 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]);

Try

	double test= test[0];

Dirk
Romain Francois
# 
Le 06/12/12 05:57, Robert A'gata a ?crit :
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