Stack is a tool to build Haskell projects and manage their dependencies. It uses the Cabal library together with (by default) a curated version of the Hackage repository.
Stack competes against Cabal's binary cabal-install and has been created as a result of the overall criticism about dependency problems. It does not, however, provide its own package format, but uses existing *.cabal files and complements projects with an additional stack.yaml file.
^"Why is stack not cabal?". Retrieved 27 January 2016. This blog post is intended to answer two very frequest questions about stack: how is it different from Cabal? And: Why was it developed as a separate project instead of being worked on with Cabal?
^"What do Haskellers want? Over a thousand tell us". Retrieved 13 January 2016. Package management with cabal is the single worst aspect of using Haskell. Asked if improvements to package management would make a difference to their future choice of Haskell for a project, 38% said it would be "crucial" and a further 29% said it would be "important". Comments connected cabal with words like hell, pain, awful, sucks, frustrating, and hideous. Only this topic showed such grave dissatisfaction.