Romain François romainfrancois

Context

Extending wrap to custom classes has always been a struggle in Rcpp, and led to the split between RcppCommon.h and Rcpp.h, the idea being that you load a "minimal" subset of Rcpp, declare your class, declare that you are going to provide a specialization of wrap, load the rest of Rcpp (the meat), and finally define your specialization.

Let's consider this template class :

template <typename T>
class MyType {} ;

This little benchmark compares the times it take to compile a really simple Rcpp example (the example you get from RStudio when you do new C++ file) with Rcpp and Rcpp11.

require(microbenchmark)
compile_Rcpp <- function(){
  Rcpp::sourceCpp("/tmp/timesTwo.cpp", rebuild = TRUE )
}
compile_Rcpp11 <- function(){
  attributes::sourceCpp( "/tmp/timesTwo.cpp" )
}

Code from this stack overflow thread

	library(purrr)
	library(github) # install_github("cscheid/rgithub")
	library(dplyr)
	library(stringr)
	library(magrittr)

	# Download issues ---------------------------------------------------------

	ctx <- interactive.login("56b637a5baffac62cad9", "8e107541ae1791259e9987d544ca568633da2ebf")
	issues1 <- get.repository.issues("hadley", "dplyr", per_page = 100)

	#include <Rinternals.h>
	#include <Rinterface.h>

	extern void* R_GlobalContext ;

	#define R_NO_REMAP
	#define USE_RINTERNALS

	#include <R.h>
	#include <Rinternals.h>

	```
	ir <- structure( iris, class = c("foo", "data.frame") )
	rbind.foo <- function(...) rbind.data.frame(...)
	rbind(ir,iris)
	# Sepal.Length Sepal.Width Petal.Length Petal.Width Species
	#ir Numeric,150 Numeric,150 Numeric,150 Numeric,150 factor,150
	#iris Numeric,150 Numeric,150 Numeric,150 Numeric,150 factor,150
	```

	So apparently we get the same as :

	# The code below will probably only work on Linux and requires VLC on the path.
	library(beepr)
	library(stringr)

	play_vlc <- function(fname) {
	system(paste("open -a vlc --args --no-loop --no-repeat --playlist-autostart --no-media-library", fname),
	ignore.stdout = TRUE, ignore.stderr=TRUE,wait = FALSE)
	}

	# Plays the mario theme while expr is executing, plays the flag pole jingle when the execution have finished.

	#include <Rcpp.h>
	using namespace Rcpp ;

	class abc {
	public:
	abc( SEXP x ) : data(x){}

	inline operator SEXP() const {
	return data ;
	}

	#!/usr/bin/R

	# this script is poorly-written, so use at your own risk.

	# ---------------------------------------------------------------
	#
	# THIS HAS A VERY GOOD CHANCE OF COMPLETELY DESTROYING YOUR REPO;
	# ONLY RUN THIS ON A COPY OF THE REPO!!!
	#
	# ----------------------------------------------------------------

	romain@naxos ~/git/Rcpp11/Rcpp11 $ brew install hiredis
	==> Downloading https://github.com/redis/hiredis/archive/v0.11.0.tar.gz
	######################################################################## 100,0%
	==> make install PREFIX=/usr/local/Cellar/hiredis/0.11.0
	🍺 /usr/local/Cellar/hiredis/0.11.0: 11 files, 156K, built in 5 seconds
	romain@naxos ~/git/Rcpp11/Rcpp11 $
	romain@naxos ~/git/Rcpp11/Rcpp11 $ R

	R version 3.1.0 (2014-04-10) -- "Spring Dance"
	Copyright (C) 2014 The R Foundation for Statistical Computing