Hello all, In our Bayesian network editor Dazzle with a wxHaskell GUI there were two places where we needed to maintain a document that can be saved to disk. And we wanted to have undo (and redo) in both places. Of course, we didn't want to write this functionality twice. After factoring out the common parts the library is so general that it might be useful for others writing editors, too. The library takes care of maintaining a document, keeping track of whether it is dirty (changed w.r.t. disk version), providing save and save as functionality, enabling and disabling menu items, updating the title bar, warning if you try to close a document that is "dirty", dealing with unlimited undo/redo and more. The reason for combining undo/redo and file management is because there is interaction between them. For example, when you save a file, the versions of the document in the undo and redo buffers become "dirty". All in all, it is quite subtle code that you don't want to write time after time. If you are writing some kind of editor and are interested in using the library, check out the (heavily documented) source code at: http://www.cs.uu.nl/~afie/pd09122004.zip The zip contains three files: 1) PersistentDocument.hs: the implementation of what is described above. This module is not dependent on wxHaskell by the way. 2) PDDefaults.hs: default implementations of the call-back functions in wxHaskell 3) PDDemo.hs: a demo application allowing you to edit a list of strings. It uses the two other files and thus supports undo/redo and cool file management for "free". In the demo file you can see how to start it. If you have suggestions for better names, need functions that are not in the interface or you have any other comment, send it to wxhaskell-users@lists.sourceforge.net At some point this functionality will be added to the wxHaskell distribution. However, I first want to let other people have a look at it and process their comments. Have fun, Arjan PS: If you want to see what our Dazzle editor looks like, go to http://www.cs.uu.nl/dazzle/