#175: cabal-install needs a new package dependency resolution algorithm ----------------------------+----------------------------------------------- Reporter: duncan | Owner: Type: task | Status: new Priority: normal | Milestone: Component: cabal-install | Version: 1.2.2.0 Severity: normal | Keywords: Difficulty: normal | Ghcversion: 6.4.2 Platform: Linux | ----------------------------+----------------------------------------------- The current package dependency algorithm is pretty simple. It's main failing is that it cannot backtrack if it finds the solution is impossible. What we would like is a new dependency resolution algorithm that can backtrack. We would also like to be able to configure policy issues separately, perhaps as a parameter. It may also be handy to let users or the system add extra version constraints. The input is the set of available packages and the output is a list of packages to install, and the assignment of configuration flags to use for each one. As for the policy input, this might take the form of a function that picks between possible dependencies in a slot, this could then allow us to make choices like preferring installed packages over the latest available package version, or vica versa. See also symptoms of the existing system: * bug #168 -- lack of configurable policy * bug #174 -- lack of backtracking -- Ticket URL: http://hackage.haskell.org/trac/hackage/ticket/175 Hackage http://haskell.org/cabal/ Hackage: Cabal and related projects