depends() prevents diff()?

• Subject: depends() prevents diff()?
• From: Robert Dodier
• Date: Thu, 11 Jun 2009 09:12:51 -0600

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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