Hello, for my studies I recently needed graph and tree handling code. Because nothing I found seemed to satisfy my needs, I finally started writing my own graph and tree module. I was especially disappointed with Data.Graph and Data.Tree. The reasons are: * The Implementation of the types is not hidden so that code using Data.Graph and Data.Tree can get very implementation-dependent. * Vertices are ints which is too low level in my opintion. I think it would be better to allow different types for vertices because this seems to closer reflect what applications demand. * I'd prefer to be able to use arbitrary sets of vertices instead of only continuous ranges. * There are only very few functions for trees and forests. Is there any interest for improving or even rewriting these two modules? Maybe, I could contribute here. For those interested in my graph and tree modules, I attached them to this mail. By the way, they don't use any non-standard features. Note that I wrote them as a part of a university project so that I'm probably not allowed to license them privately. Therefore they should be only looked at but not used in any other way. Wolfgang