package-use-list

(package-use-list package)

The packages package uses, as the keywords find-package answers (rontolisp has no package objects). The argument is any package designator — a keyword, a string, a symbol, or a package value; an unknown one signals. package-used-by-list is the inverse.

The interpreter reads its live registry. The compiled backends have no registry at run time and answer from a table baked in at compile time, so a package a compiled program creates later is invisible there.