[Hat] Hat-Gui, new tool

[Neil Mitchell]

Hi

> I agree that splitting every tool module into a "model" module with a
> nice API and a textual "view" module is a very good idea. I wouldn't yet
> introduce any directory hierarchy (the hierarchical name space isn't
> Haskell 98 anyway). I think it would be slightly more meaningful if the
> models would keep the original names and the views be named e.g.
> HatStackText.

Thats fine by me - I wouldn't have thought using hierarchical module
names would be a massive problem though, since every supported Haskell
compiler has them, and hat-trans looks as though it depends on them
(generating Hat.Something files) - but it doesn't make much difference
to me. If we ever wanted to provide Hat as a library for external
programs, as seems to be the trend (for example HsColour and Cpphs)
then hierarchical modules would be required.

> Do you plan extensions of the user interface? For a long time I thought
> it would be nice to make hat-observe source-oriented: Make it a source
> browser in which you can mark any expression and then this expression is
> observed. This could even be combined with hat-cover, because obviously
> you should not be able to observe a slice of code that was never executed.

My only planned extension is to have a continually available Source
window at the bottom of each pane, which is sync'd with the tool - for
example clicking on each line in hat-stack will jump to that line and
similarly for hat-observe. Of course, there is no reason that I can't
add links back from the source to hat-observe, and this source window
can certainly have hat-cover applied to it.

Once we have a "design" for the tool library/console split I will
commit my hat-gui and then anyone is welcome to add stuff to it!

Thanks

Neil