[otabdeveloper4]

> The mixing between parenthesis and braces and the lack of standard indentation makes some derivations really hard to read.

For sure, you're absolutely right. I'm just saying that doing that in Python would have exacerbated the problem, not made it better. (Imagine someone taking the full power of Python and unleashing it on the derivation writing process, yuck.)

[throwaway894345]

I don't think Python would be a problem. I've used it for lots of other similar configuration-esque tasks (which is what the Nix expression language is doing--producing a configuration payload that describes how to build a target) and it works well. If you really want to constrain it, there is Starlark (https://go.starlark.net) for exactly this purpose, but in practice I haven't really needed these constraints.

[elbear]

Well, if I'd have it my way, I would write the derivations in Haskell. That way, I would have a clearer picture of the different data types that flow through the build process.