A persistent version of this artifact is available at Zenodo with the link below.

ONijn is an OCaml module of Nijn. It is intended to be used as a tool to generate Coq termination certification scripts from the output of termination tools.

The current version of (O)Nijn supports higher-order polynomials in applicative format. Essentially, this is the higher-order interpretation method described in Fuhs-Kop's paper.

Check the ONijn API for more details.

We use opam to build ONijn. Make sure it is installed on your system before proceeding.

Here's the dependency list, which can be installed using opam.

• opam v2.1.3 or higher.
  • See opam for installation instructions.
• ocaml v4.14.0 or higher.
• dune v3.5.0 or higher.
• menhir v2.1 or higher.
• coq.8.16.1 is needed for formal verification.

If your current opam switch doesn't have OCaml v4.14.0 or higher, we recommend creating a fresh opam switch:

opam switch create nijn-onijn 4.14.1
eval $(opam env)
opam install dune menhir coq.8.16.1

To see the list of switches, use

opam switch

and switching to a new switch is simple. For instance

opam switch nijn-onijn

Run

dune build

to build the package from source.

opam install dune menhir

To build documentation, we use odoc.

opam install odoc

Run

dune install

to install ONijn binaries locally. This allows one to invoke the onijn binary from anywhere.

ONijn receives as input a file describing the term rewriting system and an interpretation of each function symbol in its signature. This file is called proof trace. Usually, this is a file in the format <file_name>.onijn. The file format is explained in the API.

With ONijn installed, you run it by providing an input file and an output file with the -o option.

onijn <input_file> -o <output_file.v>

The output is a Coq proof script asserting the termination of the term rewriting system described in the input file. This coq proof script can then be verified by coq, and for that one needs to install the Nijn coq library.

We provide some experiment files in the folder ./experiments/ho_poly.

Important: to run the experiments make sure the timeout utility is installed on your system. On macOS, it is available with coreutils formulae in brew.

brew install coreutils

Most Linux systems come with timeout by default.

In order to locally run the experiments, run:

make

this will build and install Nijn on your system.

The batch of experiments can be run from the script run_experiments.sh provided at the root of the project.

Next, we set executable permission to the run_experiments.sh file.

chmod oug+x run_experiments.sh

Finally, execute the run_experiments.sh file to run the experiments.

./run_experiments.sh