The environments called 'package:foo' are associated with attached packages; that is, they're located on the search path. You likely want to find the actual package namespace.
I think we have a static function Environment::namespace_env() for this. Or you can just call back to R with requireNamespace(). Kevin On Fri, Apr 13, 2018 at 10:10 PM, Wasey, Jack O <j...@jackwasey.com> wrote: > Dear all, > > It seems I can reference lazy-loaded data from an unloaded, unattached > package from R, but not using the equivalent Rcpp as described in the > quickref document. I checked out: http://dirk.eddelbuettel.com/ > code/rcpp/html/Environment_8h_source.html and even the scant references > to environments in the C API section of "Writing R Extensions" and doesn't > see what I'm missing. I suspect this is a limitation of R's C interface, > not necessarily Rcpp itself. > > I use the package nycflights13 as an example. Running `sessionInfo()` > shows the package nycflights13 is not loaded, then I run: > R --vanilla > > a <- nycflights13::flights > > Which completes without error. In Rcpp, I cannot even get a handle on the > package namespace if it is not loaded. > > Rcpp::cppFunction('Rcpp::Environment getUnloaded() { Rcpp::Environment > env("package:nycflights13"); return env;}') > getUnloaded() > Error in getUnloaded() : > Cannot convert object to an environment: [type=character; target=ENVSXP]. > > library(nycflights13) > Rcpp::cppFunction('Rcpp::Environment getUnloaded() { Rcpp::Environment > env("package:nycflights13"); return env;}') > getUnloaded() > <environment: package:nycflights13> > attr(,"name") > [1] "package:nycflights13" > attr(,"path") > [1] "/Library/Frameworks/R.framework/Versions/3.4/Resources/library/ > nycflights13" > > > > I also found that simple using `loadNamespace` was insufficient for the > Rcpp approach to work, but after `library` or `attachNamespace` the above > function does work. > > Am I treading in another rare code path? All I want to do is use a > lazy-loaded data set in an Rcpp function when the package may not be loaded > when called. Should I just be passing it as a parameter to the function? > This seems ugly. > > Using Rcpp 0.12.16, R 3.4.3 on Mac. > > Any advice appreciated. Thanks, > > Jack > > > _______________________________________________ > Rcpp-devel mailing list > Rcpp-devel@lists.r-forge.r-project.org > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel >
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