[Hat] Hat-Gui, new tool

[Neil Mitchell]

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