Using cpp4r in a package

To add cpp4r to an existing package, install it first:

install.packages("cpp4r", repos = "https://cran.r-project.org")

# or the development version:
remotes::install_github("pachadotdev/cpp4r")

Then put your C++ files in the src/ directory and add the following to your DESCRIPTION file:

LinkingTo: cpp4r

Then decorate C++ functions you want to expose to R with [[cpp4r::register]].

cpp4r is a header only library with no hard dependencies and does not use a shared library, so it is straightforward and reliable to use in packages without fear of compile-time and run-time mismatches.

Alternatively, you can vendor the current installed version of cpp4r headers into your package with cpp4r::vendor(). This ensures the headers will remain unchanged until you explicitly update them.

Getting started

See the documentation to get started using cpp4r in your scripts, particularly if you are new to C++ programming.

Getting help

Please open an issue or email me. I will do my best to respond before 48 hours.

Examples

Adding dimnames to a matrix on C++ side:

cpp4r::writable::doubles_matrix<> out(2, 2);

out(0, 0) = 1;
out(0, 1) = 2;
out(1, 0) = 3;
out(1, 1) = 4;

cpp4r::writable::list dimnames(2);
dimnames[0] = R_NilValue; // No row names
dimnames[1] = cpp4r::strings({"x1", "x2"});

out.attr("dimnames") = dimnames;

Using complex numbers (cannot be done in cpp11):

cpp4r::r_complex zero{0, 0};
cpp4r::r_complex one{1, 1};
cpp4r::r_complex two{2, 2};
cpp4r::r_complex three{3, 3};

cpp4r::writable::complexes x({one, two, three});
cpp4r::writable::complexes y({zero});

auto x_data = x.data();
y = std::move(x);

bool y.size() == 3; // true
bool y.data() == x_data; // true
bool y.is_altrep() == false; // true

Some implicit conversions for lists (cpp11 needs as_sexp() around scalars for this):

writable::list result;

double one = 1.0, two = 2.0, three = 3.0;

result.push_back({"one"_nm = one});
result.push_back(named_arg("two", two));
result.push_back({"three"_nm = 3});

writable::list result2(4);

int four = 4;
bool five = false;
const char* six = "six";
std::vector<double> seven = {7.0, 7.1, 7.2};

result2[0] = four;
result2[1] = five;
result2[2] = six;
result2[3] = seven;

result2.names() = {"four", "five", "six", "seven"};

Contributing

Contributions are welcome! Please see the internals vignette for details about design choices and coding style.

Code of Conduct

Please note that the cpp4r project is released with a Contributor Code of Conduct. By contributing to this project, you agree to abide by its terms.