Hello, I've posted undated versions of both these packages here.. http://homepages.nildram.co.uk/~ahey/HLibs/Data.COrdering/ http://homepages.nildram.co.uk/~ahey/HLibs/Data.Tree.AVL/ COrdering is needed by AVL. The AVL package has had quite a few new goodies added, including support for using AVL trees for sequences and sets. It's think it's pretty much complete now, but I can still think of a few extras that might be useful (like a "Zipper" maybe). If anybody else can think of things that would be useful but which can't be implemented easily or efficiently with the functions provided then please let me know. Regards -- Adrian Hey