Cabal ticket #500

Duncan Coutts – Saturday, 14 February 2009

all cabal community  

I just opened the 500th Cabal ticket! What, you mean there's no prize?

I'll ignore the possibility that this is a sign that Cabal is full of bugs and take the positive view that 500 tickets is a sign of an active, useful project. Nobody bothers complaining about useless projects.

As it happens, the 500th ticket is not a bug but an idea for a project. There are over 1,000 packages on Hackage now and the question is how many of them can be installed simultaneously? This is not just an idle statistic. If two packages cannot be installed with consistent dependencies then it is unlikely that you can use both together in your next project. That is of course a wasted opportunity for code re-use.

The idea is if we can work out the set of packages on Hackage that can all be installed together consistently then we can mark package pages with that information. Basically we would be handing out brownie points. Hopefully we can also influence maintainers of other packages to adjust their dependencies so that their package can also join the happy collection of packages that can all agree on their dependencies.

Actually calculating the maximal set of consistent packages is a bit tricky. It is almost certainly NP-complete in general but in practice is probably doable and we can probably live with approximations.

In fact it might make quite a good Google Summer of Code project. If you are interested, get in touch.