Hello folks in general and GwernBranwen in particular :-) I don't want to seem ungratful, but I see a lot of the old "new" collections repository has been uploaded to Hackage as separate packages but it really shouldn't be there IMHO. AFAIK most of this stuff has never been properly tested and is in any case not being actively worked on or maintained any more. AvlTree and COrdering have been thoroughly tested and are already in Hackage as separate packages. These are not being worked on or maintained by anyone either, but they are the latest official releases that anyone interested should use. The generalised trie stuff is what Jamie Brandon is working on for his GSOC project. The relevant packages are: Data-Tree-AVL 0.4 Data-COrdering 0.4 Data-Trie-General 0.4 collections-base-instances 0.4 collections-rangedsets-instances 0.4 collections-api 0.4 enumsets 0.4 collections-avl 0.4 Data-Trie-General-OrdGT 0.4 collections 0.4 Regards -- Adrian Hey