Sorry, I didn't read the original email closely enough....
2009/6/11 Robert Dodier <robert.dodier at gmail.com>
> 2009/6/11 Martin Sch?necker <ms_usenet at gmx.de>:
>
> > (%i1) depends(t, x);
> > (%o1) [t(x)]
> > (%i2) diff(t, z);
> > diff(a, z);
> > (%o2) 0
> > (%o3) 0
> > (%i4) diff(a(t), z);
> > ev(%, diff);
> > (%o4) 'diff(a(t),z,1)
> > (%o5) 'diff(a(t),z,1)
> > (%i6) dependencies;
> > (%o6) [t(x)]
>
> Looks like a bug to me. In the absence of any dependence of t on z,
> seems like diff(a(t), z) should be 0. Or have I misremembered the
> chain rule? That's entirely possible.
>
> Robert Dodier
>
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