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cpp4r helps you to interact with R objects using C++ code. It is a fork of the cpp11 package with identical syntax and similar goals.

All the documentation is here including the basic, tweaking configurations, and advanced use cases: https://cpp4r.org/.

cpp4r can be used as a replacement for cpp11 in existing or new packages. Think of cpp11 and cpp4r as MySQL and MariaDB: they are almost identical, but cpp4r has some extra features.

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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.

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Getting started

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

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Getting help

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

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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"};

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Contributing

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

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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.