Hi
Sorry for the late multiple reply, I just spent seven hours sleeping...
And ditto for my delayed reply - I've just spent 9 hours in a car on a motorway :)
I am not the maintainer of Data.Derive, nor did I write the majority of the nice code; Neil Mitchell did it, you can ask him "why replace DrIFT". However, using abstract syntax trees WAS my idea.
I would say that Stefan has written a good chunk of the code, possibly more than half, and is at very least co-maintainer :) Various others have contributed patches, which I believe fix all the errors mentioned in this thread, but if there are any outstanding please let me know. The idea of replacing DrIFT was partly because there are a few weaknesses in DrIFT, because Windows compilation was not overly fun, and because it looked something cool you could do with SYB. DrIFT has been very useful to me in the past, and exploring cool design spaces is just fun :)
You might want to note that DrIFT used to be called derive before it (amicably) changed its name due to a conflict with a product of the same name.
Hmm, I guess if its called Data.Derive then thats not a conflict, although I'll wait and see if it becomes an issue probably - Google have never complained about Hoogle so I'm expecting that one first :) One final comment, derive is still a work in progress - I haven't got as far as putting up a web page on it yet, but will make an effort to do this in the next week if its being of use to people. Thanks Neil