[Rcpp-devel] Questions on extending Rcpp wrap and as with templates

Hi everyone (and Dirk),

Second attempt on corrected email list.

I have been trying to extend Rcpp with my own wrap and as templates.

Two issues:

1) I need to explicitly call wrap. Is that expected?

So for example I wrote this specialization:

template<> SEXP Rcpp::wrap(std::vector<TimedOptDouble> const& entries) {
	std::vector<double> sec_times;
	std::vector<double> doubles;
	for(auto const& entry : entries)
	{
		sec_times.push_back(entry.GetTime().Seconds());
		TimedOptDouble::OptDouble opt_double(entry.GetOptDouble());
		if(opt_double)
			doubles.push_back(*opt_double);
		else
			doubles.push_back(R_NaReal);
	}
	return List::create(
		Named( "Time" ) = sec_times,
		Named( "Value" ) = doubles);
}

First of all, this returns what I believe to be a Rcpp::List object, which seems to be converted implicitly to a SEXP. This is the typical behaviour I know.

Unfortunately, when making use of this template, it doesn't work implicitly, but I need to explicitly call it.

So for example

SEXP GetSunPositions(SEXP a) {
	std::vector<TimedOptDouble> sun_positions;
	...
	return wrap(sun_positions);
}

works, where as

return sun_positions;

as last line doesn't. Am I doing something wrong here? I did do the declaration before including <Rcpp.h>.

2) How to make as work for own types in containers

The other way around, one can return a std::vector<double> implicitly, but how do I return std::vector<MyType>? I tried to define

	template<> MyType as(SEXP);

But that didn't help, e.g. I had to write my own

	template<> std::vector<MyType> as(SEXP);

Thanks for help

Florian

Le 6 mai 2014 ? 08:45, Florian Burkart <florian.burkart at gmail.com> a
?crit :

Hi everyone (and Dirk),

Second attempt on corrected email list.

I have been trying to extend Rcpp with my own wrap and as templates.

Two issues:

1) I need to explicitly call wrap. Is that expected?

So for example I wrote this specialization:


This is not a specialization, just another overload. You need to write a
specialization, as in:

namespace Rcpp{
template<> SEXP wrap<std::vector< TimedOptDouble > >
(std::vector<TimedOptDouble> const& entries) { ? }
}

template<> SEXP Rcpp::wrap(std::vector<TimedOptDouble> const& entries) {
 std::vector<double> sec_times;
std::vector<double> doubles;
for(auto const& entry : entries)
 {
sec_times.push_back(entry.GetTime().Seconds());
TimedOptDouble::OptDouble opt_double(entry.GetOptDouble());
 if(opt_double)
doubles.push_back(*opt_double);
else
doubles.push_back(R_NaReal);
 }
return List::create(
Named( "Time" ) = sec_times,
 Named( "Value" ) = doubles);
}

First of all, this returns what I believe to be a Rcpp::List object, which
seems to be converted implicitly to a SEXP. This is the typical behaviour I
know.


Unfortunately, when making use of this template, it doesn't work
implicitly, but I need to explicitly call it.

So for example

SEXP GetSunPositions(SEXP a) {
 std::vector<TimedOptDouble> sun_positions;
 ...
return wrap(sun_positions);
}

works, where as

return sun_positions;

as last line doesn't. Am I doing something wrong here? I did do the
declaration before including <Rcpp.h>.


This should work if you return a std::vector< TimedOptDouble > from your
function, as in:

std::vector< TimedOptDouble > GetSunPositions(SEXP a) { ? }

2) How to make as work for own types in containers

The other way around, one can return a std::vector<double> implicitly, but
how do I return std::vector<MyType>? I tried to define

template<> MyType as(SEXP);

But that didn't help, e.g. I had to write my own

template<> std::vector<MyType> as(SEXP);


This is the easiest way. A more general way would need you to express how
to handle containers of MyType, but that requires defining some traits
classes etc ? not sure it is worth the effort.

But again, you?d need to actually write a specialization: template<>
std::vector<MyType> as< std::vector<MyType> > (SEXP);

Romain


Thanks for help
Florian

From the ?quit documentation:

Hello,

I am building a package "myModule" and would like to define a function that
will be called when R is exited.

So I defined a function

RcppExport void R_unload_mlxComputeR(DllInfo *info)
{
    // Do sthg
}


and I observe that it is called when dyn.unload(myModule) is called. But the
function is not called when R is exited. I wonder if there is a similar
function (like R_exit_packgName or R_quit_packageName) that is called when R
is exited ?

 Hello,

I am building a package "myModule" and would like to define a function
that will be called when R is exited.

So I defined a function

*RcppExport void R_unload_mlxComputeR(DllInfo *info)*
*{*
*    // Do sthg*
*}*


and I observe that it is called when dyn.unload(myModule) is called. But
the function is not called when R is exited. I wonder if there is a similar
function (like R_exit_packgName or R_quit_packageName) that is called when
R is exited ?