We recommend [these install instructions](#1-installation-using-coq-platform) if you wish to install the HoTT
library to use in your own project or to play around with.

## Table of contents

- [1. Installation using Coq Platform](#1-installation-using-coq-platform)
- [2. Installation of HoTT library using opam](#2-installation-of-hott-library-using-opam)
  - [Released Versions](#released-versions)
  - [Source Versions](#source-versions)
  - [Development Versions](#development-versions)
- [3. Setup for developers (using git)](#3-setup-for-developers-using-git)
  - [3.1. Prequisites (Installing Coq)](#31-prequisites-installing-coq)
    - [3.1.1. Development in OSX and Windows](#311-development-in-osx-and-windows)
  - [3.2. Forking and obtaining the HoTT library](#32-forking-and-obtaining-the-hott-library)
  - [3.3. Building the HoTT library](#33-building-the-hott-library)
  - [3.4. Installing the library using git](#34-installing-the-library-using-git)
- [4. Editors](#4-editors)
  - [4.1. Tags for Emacs](#41-tags-for-emacs)
- [5. Updating the library](#5-updating-the-library)
- [6. Troubleshooting](#6-troubleshooting)

# 1. Installation using Coq Platform

In order to install the HoTT library, we recommend that you use the [Coq
Platform][1]. This will install the [Coq Proof Assistant][2] together with the
HoTT library. The Coq Platform supports installation on **Linux**, **MacOS** and
**Windows**.

In order to use the HoTT library in your project, make sure you have a file
called `_CoqProject` in your working directory which contains the following
lines:

```
-arg -noinit
-arg -indices-matter
```

This way when you open `.v` files using `coqide` or any other text editor for
coq (see [Editors](#editors)), the editor will pass the correct arguments to
`coq`.

To import modules from the HoTT library inside your own file, you will need to
write the following:

```coq
From HoTT Require Import Basics.
```

This, for example, will import the `Basics` module from the HoTT library. If you
wish to import the entire library you can write:

```coq
From HoTT Require Import HoTT.
```

> ### Warning
>
> The versions of the HoTT library appearing in the Coq Platform are released
> twice a year. This means that there is a good chance that the Coq Platform
> version is lagging behind the latest version of the library. If you wish to
> use the latest version of the library, you should install it using `opam` as
> described in the next section.

# 2. Installation of HoTT library using opam

## Released Versions

More advanced users may wish to install the HoTT library via `opam` ([See here
for details on installing `opam`][3]). You need to add the released coq-archive
packages to `opam` which can be done as follows:
```shell
$ opam repo add coq-released https://coq.inria.fr/opam/released
```
This will let you install the released versions of the library. We typically do
a release for each major version of `coq`. Note that the name of the HoTT
library is `coq-hott` inside the coq-archive.

```shell
$ opam install coq-hott
```

## Source Versions

After cloning the repository, you can install the library using `opam` by running
`opam install .` in the root of the repository.

## Development Versions

We also have the current development versions of the library available via
`opam`. For this however, you will need to add the dev coq-archive packages:
```shell
$ opam repo add coq-core-dev https://coq.inria.fr/opam/core-dev
$ opam repo add coq-extra-dev https://coq.inria.fr/opam/extra-dev
```

This will make `coq.dev` the latest available version of `coq`. You can pin
`coq` to a stable version by running `opam pin add coq.dev 8.19.1` for example.
Then install the library with `opam install coq-hott`, as for the released version.

# 3. Setup for developers (using git)

## 3.1. Prequisites (Installing Coq)

We recommend that you use the `opam` package manager to install `coq`. Details
about [installing Opam can be found here][3].

Using `opam` you can install the latest version of `coq` by doing the following:

```shell
$ opam install coq
```

You will also need `make` and `git` in a typical workflow.


### 3.1.1. Development in OSX and Windows

We don't recommend developing on platforms other than Linux, however it is still
possible.

Windows and OSX users may install `coq` directly using the [installer for the
appropriate coq release][9].

For OSX users `git` and `make` should be readily availble.

Windows users can install [`git` as described here][18] and [`make` as described
here][17].

## 3.2. Forking and obtaining the HoTT library

In order to do development on the HoTT library, we recommend that you [fork it
on Github][4]. More details [about forking can be found here][5].

Use `git` to clone your fork locally:

```shell
$ git clone https://github.com/YOUR-USERNAME/HoTT
```

Of course, you may clone the library directly, but for development it is
recommended to work on a fork.

To follow the rest of the instructions, it is best to change your working
directory to the `HoTT` directory.

```shell
$ cd HoTT
```

We also recommend that you [add the main repository as a git remote][6]. This
makes it easier to track changes happening on the main repository. This can be
done as follows:
```shell
$ git remote add upstream https://github.com/HoTT/HoTT.git
```

## 3.3. Building the HoTT library

In order to compile the files of the HoTT library, run `make`:

```shell
$ make
```
You can speed up the build by passing `-jN` where `N` is the number of parallel
recipes `make` will execute.

You can also use `dune` to build the library.

```shell
$ dune build
```

## 3.4. Installing the library using git

We don't recommend you install the library using the repository and instead
recommend [installing via opam](#installation-of-hott-library-using-opam),
especially if you are intending to develop the library. However the `makefile`
contains a target called `install` and therefore running
```shell
$ make install
```
will install the library.

# 4. Editors

We recommend the following text editors for the development of `.v` files:

 * [Emacs][10] together with [Proof General][11].
 * [CoqIDE][12] part of the [Coq Proof Assistant][13].
 * [Visual Studio Code][14] together with [coq-lsp][15].
 * For more editors, see the Coq website article on [User Interfaces][19].

## 4.1. Tags for Emacs

To use the Emacs tags facility with the `*.v` files here, run the command:
```shell
$ make TAGS
```
The Emacs command `M-x find-tag`, bound to `M-.` , will take you to a definition
or theorem, the default name for which is located under your cursor. Read the
help on that Emacs command with `C-h k M-.` , and learn the other facilities
provided, such as the use of `M-*` to get back where you were, or the use of
`M-x tags-search` to search throughout the code for locations matching a given
regular expression.

Dune users may use the following to generate tags:

```shell
dune build TAGS
```

# 5. Updating the library
If you installed the library via Coq Platform then [update your version of Coq
Platform][1].

If you installed the library via `opam` then simply run `opam update` and then
`opam ugprade`.

To upgrade your clone of the GitHub repository as set up in [the instructions on
using git](#forking-and-obtaining-the-hott-library): Pull the latest version
using `git pull upstream master` and then rebuild using `make` as above.

To update your fork, use `git push origin master`. We also [have tags in the
GitHub repository][7] for our released versions which you can use instead of
`master`.

# 6. Troubleshooting

In case of any problems, feel free to contact us by [opening an issue on
GitHub](https://github.com/HoTT/HoTT).


[1]: https://github.com/coq/platform/releases
[2]: https://github.com/coq/coq
[3]: https://opam.ocaml.org/doc/Install.html
[4]: https://github.com/HoTT/HoTT
[5]: https://docs.github.com/en/github/getting-started-with-github/fork-a-repo

[6]: https://docs.github.com/en/github/collaborating-with-issues-and-pull-requests/configuring-a-remote-for-a-fork
[7]: https://github.com/HoTT/HoTT/releases
[8]: https://opam.ocaml.org/doc/Install.html#OSX
[9]: https://github.com/coq/coq/releases
[10]: http://www.gnu.org/software/emacs/

[11]: http://proofgeneral.inf.ed.ac.uk
[12]: https://coq.inria.fr/refman/practical-tools/coqide.html
[13]: https://github.com/coq/coq
[14]: https://code.visualstudio.com/
[15]: https://github.com/ejgallego/coq-lsp

[16]: https://cygwin.com/install.html
[17]: https://stackoverflow.com/a/54086635
[18]: https://git-scm.com/book/en/v2/Getting-Started-Installing-Git
[19]: https://coq.inria.fr/user-interfaces.html