MAMaxGabriel·Jan 4, 2015
There are a couple questions in the comments about LTS Haskell and related projects, I was thinking this might be a good summary. (tel's might be better, but I had already written this so I'll let others decide https://news.ycombinator.com/item?id=8834823)
Hackage is the core package server, comparable to RubyGems.
The Stackage (http://www.stackage.org/) project functions like a CI system for Hackage. Stackage builds and tests the group of packages that have opted in to it, ensuring that the latest versions all work together (when there's an incompatibility between packages, the authors of the packages are pinged to resolve the issue [1]).
When a build of all the packages succeeds, Stackage generates a "snapshot", a list of all the package versions used for that build (sort of like a Gemfile.lock/Podfile.lock, for the whole ecosystem). De
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velopers can have Cabal (Haskell build tool) use the package versions from that list when installing new packages. This ensures that when you install a new package that it's compatible with the other packages you're currently using.
The issue with those snapshots (generated nightly) is that you'll want to get updates for your packages, but the snapshot generated N days from now might have packages that have made breaking API changes, making them incompatible with your application.
LTS Haskell attempts to fix that. It's based off a specific Stackage snapshot. For the duration of the LTS (currently 3 months), the major versions from that snapshot are locked down, but patches/bugfixes will continue to be released. This allows you to get bugfixes for your application while still getting the advantages of Stackage.
[1] As an example, when the language-ecmascript 0.17 package was released, the authors of the 2 packages that depended on language-ecmascript < 0.17 were pinged to update their packages: https://github.com/fpco/stackage/issues/390