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A cool implementation of normalization by evaluation (nbe) & elaboration for Cartesian cubical type theory.

For examples, see the test/ directory.

This implementation is forked from blott, the implementation artifact of Implementing a Modal Dependent Type Theory by Gratzer, Sterling, and Birkedal. Code has been incorporated from redtt, implemented by Sterling and Favonia.

A small collection of example programs is contained in the test/ directory. See test/ for a brief description of each program's purpose.


cooltt has been built with OCaml 4.13.0 with opam 2.0.8.


If you are running an older version of OCaml, try executing the following command:

$ opam switch create 4.13.0

Once these dependencies are installed cooltt can be built with the following set of commands.

$ opam update
$ opam pin add -y cooltt .              # first time
$ opam upgrade                          # after packages change

After this, the executable cooltt should be available. The makefile can be used to rebuild the package for small tests. Locally, cooltt is built with dune; running the above commands will also install dune. Once dune is available the executable can be locally changed and run with the following:

$ make upgrade-pins                     # update and upgrade dependencies in active development
$ dune exec cooltt                      # from the `cooltt` top-level directory

With Nix

First, you'll need the Nix package manager, and then you'll need to install or enable flakes.

Then, cooltt can be built with the command

nix build --impure

to put a binary cooltt in result/bin/cooltt. This is good for if you just want to build and play around with cooltt.

If you're working on cooltt, you can enter a development shell with an OCaml compiler, dune, and other tools with

nix develop --impure

and then build as in the with OPAM section above.


This research was supported by the Air Force Office of Scientific Research under MURI grants FA9550-15-1-0053, FA9550-19-1-0216, and FA9550-21-0009. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of any sponsoring institution, government or any other entity.