Le 27/04/2020 à 18:55, Toby Hocking a écrit :
Hi Dirk and Sokol, thanks for the responses.
Dirk I was aware that the C/C++ output type of wrap is always SEXP,
but I my question was about the R type/class.
Also thanks for the ref of the discussion in Sec 3.1 of the JSS 2011
article, which is pretty much what I was looking for, but it seems to
be incomplete. I can deduce from the example that std::vector becomes
a list in R, and std::map<string, int> becomes a named integer vector
in R, but I am looking for a list of all such conversions that have
currently been implemented.
I guess there is no such documentation, and we should instead refer to
the source code as Seugeui pointed out?
In that case I find it a bit problematic, because there are lots of
conversions that are possible, but not obvious upon inspection of
wrap.h. For example the std::vector -> R list conversion is not
obvious (I don't see any mention of std::vector in wrap.h actually).
Because std::vector can have any type of element, e.g. vector of
vectors, the procedure has to be generic enough. So it is realized
through iterators which are not exclusive for std::vector.
E.g. for vector of pairs <string, some_type> it is probably this
procedure which will be called:
https://github.com/sgsokol/Rcpp/blob/acf8756a75a97ee203e261412a2ab3fa7d6e15c7/inst/include/Rcpp/internal/wrap.h#L334
It will produce a named list in R.
Best,
Serguei.
As an Rcpp user I think it would be very helpful to have a list/table
that documents all the currently implemented conversions. Would that
be very difficult to write by hand / generate from the source code?
On Sun, Apr 26, 2020 at 12:07 AM Sokol Serguei <so...@insa-toulouse.fr
<mailto:so...@insa-toulouse.fr>> wrote:
Le 26/04/2020 à 01:19, Dirk Eddelbuettel a écrit :
> On 25 April 2020 at 16:04, Toby Hocking wrote: | Hi, can someone
> please tell me where the return types of wrap are | documented? The
> _return_ value of a wrap() call is by definition always SEXP.
Just how
> the _input_ for as<>() converters is always a SEXP. For wrap(), see
> e.g. Section 3.1 of the JSS 2011 paper which ships as vignette
> Rcpp-jss-2011.pdf
To complete the Dirk's response, this gallery example can be of
some help:
https://gallery.rcpp.org/articles/custom-templated-wrap-and-as-for-seamingless-interfaces/
And as always, an ultimate place to clarify the trickiest
questions is
the code itself ;) :
https://github.com/sgsokol/Rcpp/blob/master/inst/include/Rcpp/internal/wrap.h
Best,
Serguei.
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