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I have the following function:

Q[r_, f_, s0_] := Q[r, f, s0] = F[r, s0] D[f[s0], s0]

By calling

Q[r, Q[r, f, s0], s0]

I obtain the following result:

F[r,s0] ((F[r,s0] f'[s0])'[s0]+(F[r,s0] f''[s0]+f'[s0] F^(0,1)[r,s0])[s0])

when the desired answer is

F[r,s0](F[r,s0] f''[s0]+f'[s0] F^(0,1)[r,s0])

Could you please help me to obtain the correct answer?

Thank you in advance for all your help!

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1 Answer 1

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The issue and solution are similar to the one in your previous post. In addition, we need to give Q the attribute HoldAll:

ClearAll[Q, f, F]
SetAttributes[Q, HoldAll]
Q[r_, f_, s0_] :=  Q[r, f, s0] = F[r, s0]  D[f[s0], s0]
Q[r_, f_[r_, g_, s0_], s0_] := F[r, s0] D[f[r, g, s0], s0]

Q[r, f, s0]
 F[r,s0] (f^′)[s0]
Q[r, Q[r, f, s0], s0]
F[r,s0] (F[r,s0] (f^′′)[s0]+(f^′)[s0] (F^(0,1))[r,s0])
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  • $\begingroup$ Thank you very much! $\endgroup$
    – Svetlana
    May 29, 2020 at 19:38
  • 1
    $\begingroup$ @Svetlana, you are welcome. And welcome to mma.se. $\endgroup$
    – kglr
    May 29, 2020 at 20:01

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