Mugda

An implementation of the Mugda paper by Karl Mehltretter.

The "Mu" of the name "Mugda" comes from μ-operator (mu-operator) of general recursive function.

Notes about our implementation:

• Use S-expression as overall syntax, to expression ideas clearly.
• Close to the paper, so that the code is easy to be reviewed with the paper.
• Add comments about alternative ways to implement the same ideas.
• Do not follow bad naming conventions of the paper.

Usages

Use our server

mugda-server: A server that can run mugda code.

Run a file:

curl https://mu.cic.run --data-binary @docs/tests/basic/let.test.mu

Run multiline text (bash and zsh):

curl https://mu.cic.run --data-binary @- << END

(data Nat () ()
  (zero () Nat)
  (add1 ([prev Nat]) Nat))

(fn add (-> Nat Nat Nat)
  [(x (zero)) x]
  [(x (add1 y)) (add1 (add x y))])

(add (add1 zero) (add1 zero))

END

Command line tool

Install it by the following command:

npm install -g @cicada-lang/mugda.sexp

The command line program is called mu.

open a REPL:

mu repl

or just:

mu

Run a file:

mu run docs/tests/basic/id.test.mu

Run a file and watch file change:

mu run docs/tests/basic/id.test.mu --watch

Run a URL:

• All files in this repo, can be fetched from: https://cdn.mu.cic.run/<path>, and any other http server that serves .mu code would also work.

mu run https://cdn.mu.cic.run/docs/tests/basic/id.test.mu

Notes

Zero arity data constructor

When using zero arity data constructor, we must write them in (). For example, zero and (zero) are the same.

But when using zero arity data constructor in pattern, we must write them in (). For example, we should not write zero but write (zero), otherwise the interpreter can not distinguish pattern variable from this zero arity data constructor.

Syntax of inductive datatype definition

The syntax of inductive datatype definition -- (data), is learnt from "The Little Typer".

Examples

TODO

Please see docs/tests/ for more examples.

Development

npm install           # Install dependencies
npm run build         # Compile `src/` to `lib/`
npm run build:watch   # Watch the compilation
npm run format        # Format the code
npm run test          # Run test
npm run test:watch    # Watch the testing

Thanks

Thank you, Karl Mehltretter, for writing this paper.

Contributions

To make a contribution, fork this project and create a pull request.

Please read the STYLE-GUIDE.md before you change the code.

Remember to add yourself to AUTHORS. Your line belongs to you, you can write a little introduction to yourself but not too long.

It is assumed that all non draft PRs are ready to be merged. If your PR is not ready to be merged yet, please make it a draft PR:

• Creating draft PR
• Changing a PR to draft

During the development of your PR, you can make use of the TODO.md file to record ideas temporarily, and this file should be clean again at the end of your development.

License

GPLv3