don't see what proto has to do with this. Or I still don't understand what proto is intended for. Well, I would guess that if this is built out with proto, it will make it much easier and standard to generalize your own functions and for boost math to implement this for all of theirs. Or maybe I was just trying to sell the proto/expression template guys on getting interested in this problem because they are all geniuses.
I know little about proto, and could not imagine right now what spesific problem/domain is suitable for it. But I have the same feeling as yours, that utilizing proto in domain like AD and other numeric ones will probably make things even cooler. I also want to raise those geniuses'(including Steven) interests in digging deeper in these fields. :-) B/Rgds Max