(image courtesy of @tranngocma)

What is RedPRL?

RedPRL is the People's Refinement Logic, a next-generation homage to Nuprl; RedPRL was preceeded by JonPRL, written by Jon Sterling, Danny Gratzer and Vincent Rahli.

The purpose of RedPRL is to provide a practical implementation of Computational Cubical Type Theory in the Nuprl style, integrating modern advances in proof refinement.

Literature and background on RedPRL

RedPRL is (becoming) a proof assistant for Computational Cubical Type Theory, as described by Angiuli, Favonia, and Harper in Computational Higher Type Theory III: Univalent Universes and Exact Equality. The syntactic framework is inspired by second-order abstract syntax (relevant names include Aczel, Martin-Löf, Fiore, Plotkin, Turi, Harper, and many others).

What is this repository?

This is the repository for the nascent development of RedPRL. RedPRL is an experiment which is constantly changing; we do not yet have strong documentation, but we have an IRC channel on Freenode (#redprl) where we encourage anyone to ask any question, no matter how silly it may seem.

How do I build it?

First, fetch all submodules. If you are cloning for the first time, use

git clone --recursive [email protected]:RedPRL/sml-redprl.git

If you have already cloned, then be sure to make sure all submodules are up to date, as follows:

git submodule update --init --recursive

Next, make sure that you have the MLton compiler for Standard ML installed. Then, simply run

./script/mlton.sh

Then, a binary will be placed in ./bin/redprl, which you may run as follows

./bin/redprl example/README.prl

Editor Support: Vim

Our best-supported editor is currently Vim. See the RedPRL plugin under vim/.

Editor Support: Visual Studio Code

The easiest/most user-friendly way to get started is with Visual Studio Code; the RedPRL mode can be downloaded from the Marketplace.

Editor Support: Emacs

We have support for interactive RedPRL development in Emacs.

The Emacs mode is a part of this repository. Additionally, it is available in MELPA.

The easiest way to install the package is from MELPA, using their getting started instructions. The package is named redprl. It will probably be necessary to set the customization variable redprl-command to the path to the redprl binary.

When redprl-mode is installed, files ending in .prl will automatically open in the mode. If they do not, run M-x redprl-mode. The mode supports the following features:

• Press C-c C-l to send the current development to RedPRL.

• Imenu (or wrappers such as helm-imenu) can be used to jump to definitions in the buffer.

• Completion is supported for names of declarations in the current buffer.

• Flycheck is also supported, and can be used in lieu of C-c C-l if you like. Be sure that either the redprl executable is in your path, or set flycheck-redprl-executable in your own Emacs configuration.

Contributing

If you'd like to help, the best place to start are issues with the following labels:

• E-easy
• E-help-wanted

We follow the issue labels used by Rust which are described in detail here.

If you find something you want to work on, please leave a comment so that others can coordinate their efforts with you. Also, please don't hesitate to open a new issue if you have feedback of any kind.

The above text is stolen from Yggdrasil.

Acknowledgments

This research was sponsored by the Air Force Office of Scientific Research under grant number FA9550-15-1-0053 and the National Science Foundation under grant number DMS-1638352. We also thank the Isaac Newton Institute for Mathematical Sciences for its support and hospitality during the program "Big Proof" when part of work on this paper was undertaken; the program was supported by the Engineering and Physical Sciences Research Council under grant number EP/K032208/1. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of any sponsoring institution, government or any other entity.