Cython vs Opal

Cython is a free compiler for Python and the extended Cython language, used to create C extensions for Python. It translates source code into C or C++ that can be built as Python extension modules. Optional static type declarations can help produce more efficient C, while declared C and C++ types let Python code call existing C or C++ code. Cython supports source-level debugging across Python, Cython and C, and the project describes uses including wrapping external libraries, embedding CPython in applications and speeding up Python code with C modules. It can work with multidimensional NumPy arrays and integrate with low-level libraries and applications. Installation is available through pip, and some scientific Python distributions bundle it. A C compiler is required, with installation guidance for Linux, macOS and Windows. The project describes compatibility with major C and C++ compilers for CPython 3.8 and later, and characterizes PyPy support as mostly usable. Limited API and free-threading CPython support in Cython 3.1 are experimental. Cython is available under the Apache 2.0 License.

Opal is a Ruby-to-JavaScript source-to-source compiler that converts Ruby ahead of time into plain JavaScript, without a runtime interpreter. It includes implementations of Ruby core and standard libraries. Ruby code can call JavaScript, JavaScript can call Ruby, and native JavaScript classes can be treated as Ruby classes. The project describes sharing a gem, objects, and specs between server and client code.

Opal can run in browsers and JavaScript environments including Node.js, Deno, Bun, and QuickJS. For its upcoming 2.0 release, the project lists current and previous stable Firefox, Chrome, Safari, and Edge as supported, while Internet Explorer is unsupported. That release targets ES2021 and has no transpilation fallback for older JavaScript engines. Listed integrations include Rails, Sinatra, Roda, and static apps; the Rails example uses opal-rails and requires opal_ujs and turbolinks. Installation is through `gem install opal` or by adding the gem to a Gemfile. The gemspec declares Ruby >= 2.3, and CI exercises Ruby 3.0 through 4.0 and JRuby. Opal is MIT-licensed and free, with CLI and API access. Support channels include Slack, Stack Overflow’s #opalrb tag, and GitHub issues.