24 Days of Hackage: Cabal

Over the next 24 days I’m going to be posting a series of reviews on some of my favourite libraries on Hackage. This will be a whirlwind tour of some modules that I use on an almost daily basis, including modules that have inspired me, modules that have changed the way I think about code, and some modules that are so amazing I’m not even smart enough to use them!

I’m motivated to do this after spending a few years in the Perl community, which often has advent calendars - some notable ones include the Perl 6 advent calendar, the Catalyst advent calendar, and many more. I’ve got a lot out of those calendars in the past, and I haven’t seen any for Haskell yet. I hope I can inspire some people with these posts to try their own advent calendars, they are a fantastic resource for knowledge sharing.

As a quick disclaimer, I don’t think I’m really an expert on much of the stuff I’m going to be writing about, but if I can introduce at least one person to one new idea, then I’ll happily call this project has been a success. So, with that out of the way, lets get on with the show - and what better project to begin with than Cabal!

Cabal, the Common Architecture for Building Applications and Libraries, is a set of libraries and tools for managing the packaging and deployment of Haskell projects. Cabal is undeniably one of the most used tools by the working Haskell programmer, and while it’s not perfect it’s certainly one of the slickest packaging tools I’ve used in all the languages I’ve worked with.

At a basic level, Cabal will let you specify some basic metadata about your project - the name of it, some version information (and even that is formally specified, in true Haskell spirit), copyright information and dependencies. One thing I really like about the cabal format is that in a single .cabal file I can package multiple executables along with a library. This has really helped me create small, single purpose applications, while also structuring my code cleanly. The cabal format is expressive too - you can get up and running with a really basic file, but it certainly scales to custom build types and all sorts of trickery, if that’s what you need.

Cabal has great integration with other tools in the Haskell eco-system, with built in support for Haddock for documentation, HPC for code coverage, and a flexible way of specifying both test suites and benchmarks. I really like the ability to maintain a local set of documentation for all installed modules by setting documentation: True in my ~/.cabal/config configuration file - this has been a life saver several times on long commutes!

Of course, the biggest selling point of cabal is that you get access to all of Hackage - which is exactly what this series will be about! So, if you want to experiment with things I’m about to blog about, I recommend you grab yourself the latest Haskell platform, run cabal update and get ready to start living in GHCi!

You can contact me via email at ollie@ocharles.org.uk or tweet to me @acid2. I share almost all of my work at GitHub. This post is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

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