Hi Mads, > I was surprised to find, that Nix do not alleviate the dependency > hell as thoroughly as I thought.
yes, statements like those should be taken with a grain of salt. It's mostly propaganda. Basically, Nix does not affect the package dependency structure in any way whatsoever. A package that's being installed via Nix has the exact same dependencies it would have if you'd install it on Gentoo, Debian, or any other distribution. What can be said for Nix is that it is particularly good at detecting unspecified dependencies. Arguably, the package dependency structure expressed in nixpkgs is more complete and accurate than that of other distributions, but it's by no means simpler, easier to maintain, or easier to understand. > If each package, in the Nix subversion repository, explicitly stated > which versions of packages it depended upon, then upgrading library X > would be safe. That can easily be done. Packages *can* depend on specific versions of other packages. While possible, however, this kind of setup is undesirable. Consider a package that depends on Python 2.4. Now there is another package that depends on Python 2.5. If you install those two packages, you'll end up having two different versions of Python's installed. If you consider this phenomenon for a complete Linux system with OpenOffice and Firefox and whatnot else, then you'll have an installation that is incredible redundant. In truth those two packages don't really depend specifically on Python 2.4 or 2.5. It's more likely that they'll work fine with any version of Python newer than, say 2.0. Then again, Python 3.0 might break them, so what you really want to specify is a version range: "python>=2.0 && python<=3.0" Nix can do all that. The reason why dependencies aren't specified that way isn't technical in nature. The problem is just that figuring out those facts is a hell of a lot of work. :-) Take care, Peter _______________________________________________ nix-dev mailing list nix-dev@cs.uu.nl https://mail.cs.uu.nl/mailman/listinfo/nix-dev
