tatara-eval — an optimized in-memory Lisp interpreter.
Takes Sexp from tatara-lisp, evaluates to Value. Produces typed
Derivation values via the derivation builtin, which tatara-nix::realize
then builds into concrete store paths (either our own store or the live
/nix/store on disk).
source ──read──► Sexp ──eval──► Value
│
▼ (if Derivation)
tatara-nix::realize
│
▼
StorePath
The interpreter is Rust-bordered (you get a typed Derivation or a typed
error, never a partially-built thing), Lisp-authorable, and cheap to
clone thanks to Arc-backed Value cells. A future &'arena form can
replace the Arcs without changing the public API.