Appendix A - Haskell Tools Setup

Here I discuss the stack build tool but as I update this book in September 2024, I now frequently just use Cabal to build and run projects. The README files for the examples in the GitHub repository for this book usually have directions for both stack and Cabal.

I recommend that if you are new to Haskell that you at least do a minimal installation of stack and work through the first chapter using an interactive REPL. After experimenting with the REPL then do please come back to Appendix A and install support for the editor of your choice (or an IDE) and hlint.

I assume that you have the Haskell package manager stack installed. If you have not installed stack yet please follow these directions.

After installing stack and running it you will have a directory “.stack” in your home directory where stack will keep compiled libraries and configuration data. You will want to create a file “~/.stack/config.yaml” with contents similar to my stack configuration file:

1 templates:
2   params:
3       author-email: markw@markwatson.com
4       author-name: Mark Watson
5       category: dev
6       copyright: Copyright 2016-2024 Mark Watson. All rights reserved
7       github-username: mark-watson

Replace my name and email address with yours. You might also want to install the package manager Cabal and the “lint” program hlint:

1 $ stack install cabal-install
2 $ stack install hlint

These installs might take a while so go outside for ten minutes and get some fresh air.

You should get in the habit of running hlint on your code and consider trying to remove all or at least most warnings. You can customize the types of warnings hlint shows: read the documentation for hlint.

I have already created stack projects for the examples in this book. When you have worked through them, then please refer to the stack documentation for creating projects.

There are several good alternatives to using the Emacs editor but Emacs with haskell-mode is my favorite environment. There are instructions for adding haskell-mode to Emacs on the project home page on github. If you follow these instructions you will have syntax hi-liting and Emacs will understand Haskell indentation rules.

I recommend and use the Intero Emacs package to get auto completions and real time syntax error warnings. Intero is designed to work with stack.

I add the following to the bottom of my .emacs file:

(add-hook ’haskell-mode-hook ’intero-mode)

and if Intero is too “heavy weight” for my current project, then I comment out the add-hook expression. Intero can increase the startup time for Emacs for editing Haskell files. That said, I almost always keep Intero enabled in my Emacs environment.

hlint is a wonderful tool for refining your knowledge and use of the Haskell language. After writing new code and checking that it works, then run hlint for suggestions on how to improve your code.

Install hlint using:

1 stack install hlint