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Polyglot is a collection of examples of how to interface pieces of code written in different languages, and/or execute code in a runtime environment that's not traditional for its language. Calling a C++ library from a Python program, or executing OCaml code in a web browser, are two examples amongst what Polyglot demonstrates. Have a look at the examples.

For the time being, it focuses on the following runtime environments:

  • Native: code compiled for the native CPU
  • Interpreted: code run by an interpreter, itself compiled for the native CPU
  • Web browser and Node.js (below, JS): code translated to JavaScript and run by an interpreter un a JavaScript environment

And the following languages (with their traditional runtime environment):

Questions? Remarks? Bugs? Want to contribute? Open an issue!


Reasons to use several programming languages in the same program:

  • reuse: a new program calls an existing code base in another language
  • sharing: the same code runs on several environments
  • performance: a part of a program is compiled natively for execution speed while other parts are interpreted to ease development

Running the examples

To run all the examples provided in this project, you need a reasonably recent version of Bash (other shells might work but are not supported), and a reasonably recent version of Docker.

Then ./ should run each example in Docker containers. The first time you run it, it will download and install many things in Docker images; be patient. You may want to use the --verbose flag to see what's going on. You can also limit the scope that you run by passing arguments to the script, e.g. ./ examples/C-runs-in-JS.

Code organization

The shared directory contains code that doesn't change from one example to the other. For example, this could be the legacy code you're trying to use as a guest. This organization shows that it can be used as-is (through a wrapper though).

The examples directory contains code specific to each example. Each example contains:

  • the source code specific to that example
  • symbolic links to the shared files used in that example
  • a shell script to... build that example and run it

The tools used in are installed in a Dockerfile found somewhere up the directory hierarchy. For example, the Dockerfile used to run example examples/C++-calls-C/extern-C/integers is examples/C++-calls-C/Dockerfile.

Examples are classified by several criteria captured by each directory level. The first level tells the language(s) and execution environment (e.g. C++-calls-C, OCaml-runs-in-JS), the second level is the method used (e.g. C-compiled-as-C++), and the next levels are variants (see below).


Variants in examples take their names from variants in shared. Each variant can be seen as a collection of examples. Some variants are closely related (e.g. "Calling a guest language" below), and some are mostly independent.

Running in unusual environments

The X-runs-in-E/hello variant is the simplest way to demonstrate running code in a non-traditional environment: displaying a simple "Hello" message.

Calling a guest language

The simplest way to demonstrate a host language calling a function written in a guest language is to use a function that takes no argument and returns nothing (void guest() in C/C++). This is the X-calls-Y/side-effect variant.

The X-calls-Y/integers variant is slightly more sophisticated as it involves passing integer arguments to the guest and returning an integer to the host.

The X-calls-Y/callback variant is more advanced and shows how the guest code can call a function (a callback) passed in by the host code.


Examples of programs written in several languages



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