[Rcpp-devel] Value type of DataFrame::operator[]

What about using "TYPEOF"? Please see R Internals (
https://cran.r-project.org/doc/manuals/r-release/R-ints.html#SEXPTYPEs) for
more details.

#include <Rcpp.h>

using namespace Rcpp;

// [[Rcpp::export]]
DataFrame rcpp_df(){
  NumericVector   numeric = {1,3};
  IntegerVector   integer = {1,3};
  CharacterVector character = {"B","D"};
  LogicalVector   logical = {false, true};

  DataFrame df = DataFrame::create(Named("numeric") = numeric,
                                Named("integer") = integer,
                                Named("character") = character,
                                Named("logical") = logical);

  Rcpp::Rcout << "numeric:" << TYPEOF(df["numeric"]) << std::endl;
  Rcpp::Rcout << "integer:" << TYPEOF(df["integer"]) << std::endl;
  Rcpp::Rcout << "character:" << TYPEOF(df["character"]) << std::endl;
  Rcpp::Rcout << "logical:" << TYPEOF(df["logical"]) << std::endl;

  return df;
}

/*

Rcpp::sourceCpp("test.cc")
df <- rcpp_df()

numeric:14
integer:13
character:13
logical:10
*/

Is there a way to discover the value type for the result of calling
DataFrame::operator[]?  For example, is there a metafiction that will
deduce the type?

A similar question could be asked about the result of calling
Vector::operator[].

I understand that these functions actually return a proxy, but it would be
very helpful to find out the underlying value type.

Thanks for your help.

Cheers,
Brook

_______________________________________________
Rcpp-devel mailing list
Rcpp-devel at lists.r-forge.r-project.org
https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.r-forge.r-project.org/pipermail/rcpp-devel/attachments/20191206/eb615b4b/attachment.html>