Maxima 5.25.1: integrate is buggy



> either "at" is trying to be super careful, or it's missing some
> simplifications:
>
>   (%i15) at(diff(f(t),t),x=9);
>   (%o15) at('diff(f(t),t,1),x=9)

Robert Dodier wrote:

> Hmm, I suppose f might use x as a global variable ....

Maxima doesn't give an "at" nounform for at(f(z),x=9).  Maybe that is a bit inconsistent with  at(diff(f(t),t),x=9) --> an "at" nounform?

--Barton (not fan of global variables)