Cython vs js_of_ocaml

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.

js_of_ocaml compiles OCaml bytecode programs into JavaScript for browsers and Node.js. It works with an existing OCaml installation and does not require libraries to be recompiled. Installation is available through opam, while Dune supports separate compilation in development and whole-program compilation in release builds. Whole-program compilation performs global dead-code elimination and cross-module optimization. The library provides a typed bridge between OCaml and JavaScript, including PPX syntax for properties, methods, constructors and objects. Browser bindings cover the DOM, Fetch, WebSockets, WebGL, workers and typed arrays. Optional packages add Lwt support, TyXML, JSON derivation and an OCaml toplevel in the browser. Documented targets include Node.js 18 or later, QuickJS-NG and modern ECMAScript 2020 browsers, including Chrome 80+, Firefox 74+, Safari 13.4+ and Edge 80+. Requirements include OCaml 4.13–5.5, Dune 3.20 or later and Menhir. The project is free and open source.