Diff currently allows constants as a second argument; I've assigned
the bug<https://sourceforge.net/tracker/?func=detail&aid=3487920&group_id=4933&atid=104933>to
myself (the fix is trivial).
It also allows:
diff(x,tan(x)) => 0
diff(x,f(x)) => 0
but not
diff(x,1+x) => error
In principle, all of these could of course be meaningful, but Maxima
doesn't know that.
Which seems more useful for users in such cases?:
* Giving an error?
* Leaving as noun forms? (which Maxima can't do anything useful with)
I suspect that in most cases, an error would be welcome....
-s