Millet

Do you, like me, test theoretical programming language concepts by building your own programming language? Do you, like me, do it by copying and modifying your most recent language because you are too lazy to build everything from scratch? Do you, like me, end up with a mess? Then Millet is for you. It is a pure ML-like language with simple and modular codebase that you can use as a template for your next language.

How to install and run Millet?

Install dependencies by

opam install menhir ocaml-vdom ocamlformat

and build Millet by running (requires OCaml >= 4.14.0)

make

and you can clean up by running

make clean

Millet gives you two options to run programs:

• The first option is a web interface, accessible at web/index.html, which allows you to load one of the built-in examples or enter your own program, and then interactively click through all its (non-deterministic and asynchronous) reductions or introduce external interrupts. The web interface is also available at https://matija.pretnar.info/millet/.

• The second option is a command line executable run as

  ./cli.exe file1.mlt file2.mlt ...
  

  which loads all the commands in all the listed files and starts evaluating the given program, displaying all outgoing signals and the terminal configuration (if there is one). Non-deterministic reductions are chosen randomly and there is no option of introducing external interrupts. If you do not want to load the standard library, run Millet with the --no-stdlib option.

How to use Millet as a template?

The easiest way is to first create an empty repository:

mkdir the-best-language
cd the-best-language
git init

Next, add Millet's remote repository:

git remote add millet [email protected]:matijapretnar/millet.git
git fetch millet

Then, create two branches, one for your main development and one for tracking Millet:

git branch --no-track main millet/main
git branch --track millet millet/main
git checkout main

Now, each time Millet updates, you can run

git checkout millet
git pull
git checkout main
git merge millet

to pull latest changes and merge them into your main development.

Why the name Millet?

Millet uses fine-grain call-by-value core calculus, and there is no finer grain than millet. Plus, the .mlt extension fits nicely into the ML family.