Reading back my own mail, I can see that I probably wasn't explicit enough about the interface change. Sorry about that. I'm suggesting that there be higher-level interfaces to weak-list-like data structures. - "Simple" weak lists have weak-list-car and weak-list-cdr. - The various types of weak alists have higher-level functions to access them like: weak-list-add-association weak-list-assq weak-list-assoc weak-list-map weak-list-mapc ... This way, people don't need access to the representation. -- Cheers =8-} Mike Friede, Völkerverständigung und überhaupt blabla