Tree stuff and other fun

[Neil Booth <neil at daikokuya dot demon dot co dot uk>]

The tree documentation in c-tree.texi is not complete; so whilst
learning more about trees I thought I would add to it as I went along.

However, that can rapidly get boring in and of itself, so I'd like to
actually do something involving trees too; you learn much better when
doing stuff and breaking it.

I've scanned the projects list for tree-related things, and there only
seems to be the ast-optimizer-branch, which has too much non-tree
stuff for me to be interested at present, and probably is beyond my
current understanding.

So, can anyone suggest some tree-related projects to work on?  Something
not too hard and achievable is preferable.  I've heard occasional grunts
about the following:

1) Getting rid of SAVE_EXPRs
2) Making trees more language independent (in particular, not being so
   C-ish).

Is 1) very hard, or achievable?  2) is obviously a big job, but are
there any smaller steps I could make towards that goal?

Or anything else?  Suggestions welcome!

Neil.