Introducing cpp4r: A C++ Interface for R’s C Interface

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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.

• Code: https://github.com/pachadotdev/cpp4r.
• Documentation: 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.

After discussing some pull requests with Hadley Wickham from Posit, it was mentioned that I should create my own fork to add the following features:

• Convert ordered and unordered C++ maps to R lists.
• Roxygen support on C++ side.
• Allow dimnames atribute with matrices on C++ side.
• Support nullable external_ptr<>.
• Use values added to a vector with push_back() immediately.
• Support bidirectional passing of complex numbers/vectors.
• Provide flexibility with data types (e.g., cpp4r’s as_integers() and as_doubles() accept logical inputs while cpp11’s do not).
• Some internal optimizations for better speed (e.g., https://github.com/r-lib/cpp11/pull/463 and https://github.com/r-lib/cpp11/pull/430).

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Using cpp4r in a package

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

remotes::install_github("pachadotdev/cpp4r")

# or
pak::pkg_install("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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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.