a unique Ruby implementation, transpiled to C++ (WIP)
Update URLs for Natalie now that we have our own org! :-)
C2: fix bugs setting certain method args
C2: fix bug setting existing variable from higher scope


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You can also use your local clone with git send-email.


github build status builds.sr.ht status MIT License

Natalie is a very early-stage work-in-progress Ruby implementation.

It provides an ahead-of-time compiler using C++ and gcc/clang as the backend. Also, the language has a REPL that performs incremental compilation.

demo screencast

There is much work left to do before this is useful. Please let me know if you want to help!

#Helping Out

Contributions are welcome! You can learn more about how I work on Natalie via the hacking session videos on YouTube.

The easiest way to get started right now would be to find a method on an object that is not yet implemented and make it yourself! Also take a look at good first issues. (See the 'Building' and 'Running Tests' sections below for some helpful steps.)

We have a very quiet Discord server -- come and hang out!


Natalie is tested on macOS, OpenBSD, and Ubuntu Linux. Windows is not yet supported.

Natalie requires a system Ruby (MRI) to host the compiler.


  • git
  • autoconf
  • automake
  • libtool
  • make
  • gcc or clang
  • Ruby 2.7.x or Ruby 3.0.x (rbenv preferred)
  • ccache (optional)

Install the above prerequisites on your platform, then run:

git clone https://github.com/natalie-lang/natalie
cd natalie

NOTE: Currently, the default build is the "debug" build, since Nataile is in active development. But you can build in release mode with rake build_release.




Run a Ruby script:

bin/natalie examples/hello.rb

Compile a file to an executable:

bin/natalie examples/hello.rb -c hello

#Using With Docker

docker build -t natalie .                                            # build image
docker run -it --rm natalie                                          # repl
docker run -it --rm natalie -e "p 2 * 3"                             # immediate
docker run -it --rm -v$(pwd)/myfile.rb:/myfile.rb natalie /myfile.rb # execute a local rb file
docker run -it --rm --entrypoint bash natalie                        # bash prompt

#Running Tests

To run a test (or spec), you can run it like a normal Ruby script:

bin/natalie spec/core/string/strip_spec.rb

This will run the tests and tell you if there are any failures.

If you want to run all the tests that we expect to pass, you can run:

rake test

Lastly, if you need to run a handful of tests locally, you can use the test/runner.rb helper script:

bin/natalie test/runner.rb test/natalie/if_test.rb test/natalie/loop_test.rb

#What's the difference between the 'spec/' and 'test/' directories?

The files in spec/ come from the excellent ruby/spec project, which is a community-curated repo of test files that any Ruby implementation can use to compare its conformance to what MRI (Matz's Ruby Intepreter) does. We copy specs over as we implement the part of the language that they cover.

Everything in test/ is stuff we wrote while working on Natalie. These are tests that helped us bootstrap certain parts of the language and/or weren't covered as much as we would like by the official Ruby specs. We use this to supplement the specs in spec/.

Natalie is copyright 2021, Tim Morgan and contributors. Natalie is licensed under the MIT License; see the LICENSE file in this directory for the full text.

Some parts of this program are copied from other sources, and the copyright belongs to the respective owner:

file(s) copyright license
dtoa.c David M. Gay, Lucent Technologies custom permissive
fiber_object.* Evan Jones MIT
big_int.* Syed Faheel Ahmad MIT
spec/* (see spec/LICENSE) Engine Yard, Inc. MIT
version.rb Engine Yard, Inc. MIT

See each file above for full copyright and license text.