I’ll save here a reddit discussion, which I find interesting but that will be burried quickly down reddit’s history. The goal is to get all the dependencies of a system. You’d better read the OP’s question and the discussion (where the OP is the experimented svetlyak40wt/40ants, at the moment doing a god’s work on Weblocks). His solution is https://gist.github.com/svetlyak40wt/03bc68c820bb3e45bc7871870379c42e (ql:quickload :fset) (defun get-dependencies (system) "Returns a set with ...