Hi, I have started writing Hat-Gui, a screenshot is available at: http://www-users.cs.york.ac.uk/~ndm/projects/hat-gui.png It is written with Gtk2Hs, and should be cross platform. This screenshot is slightly misleading, only hat-stack works, the other two tabs are just dummy's. However, hat-stack works perfectly, and you can open a hat file, or associate them in your Windows environment. In order to get hat-stack working I copied the HatStack.hs program, renamed it to HatStackLib.hs and tweaked it a bit. Obviously this is not the best way to do it. In order to get hat-gui working properly it would be best to split every hat tool into a module which exports a Haskell API interface (i.e. HatTools.Stack) and a command line program that imports that as hat-stack. What is the best way to acheive this split, and how should it be organised? Most of the tools are already relatively abstract - although will probably need tweaks. Thanks Neil