NixOS is valued for its deterministic and reproducible functional package manager, Nix. Users can construct and rebuild an entire operating system by inputting Nix DSL, allowing for incremental changes and precise control over the system.

Curried functions define n-parameter functions by applying one argument at a time, returning a new function for the subsequent parameters. This technique is common in purely functional programming languages, allowing for a more modular and flexible approach to function application.