Guix and Nix don’t actually solve constraint problems, though. By design, they omit the dependency resolution that other package managers do, and humans manage the dependencies. If you want to change versions, you need to do some hacking to update things and propagate requirements through the package graph.

You could think of Spack (github.com/spack/spack) as a nix/guix-like model, but with a solver. Spack uses ASP (which is prolog-like but reduces to SAT with optimization) but packages are written in an embedded python DSL.

Would it be possible to write a CLI tool that translated Scheme into Nix-compatible config files? Presumably then you could alias Nix commands so they piped config 8n through the translator.

It might be possible, but a better approach (and the one Guix used initially, iirc) is to just be compatible with the derivation format (kinda like object files in C/C++ compilation). The end result is basically a big dependency graph, so one may be able to write a different generator in front of it.

Anyone who has done the basics in Prolog could "logically" pull this off (e.g. some rule requires another rule, or however Prolog works; it's been a long time since I looked at it), but all of the extra stuff in the library (e.g. all of the systemd tweaking, interface, etc) is a LOT of man hours.

I heard about Spack [0] on a recent cppcast episode, which seems like a competitor to Nix (but from the supercomputing side of things), but I don't know if they do the OS-level stuff (vs. nix shell / conda / pip / gem replacement stuff).

[0] https://spack.io/