It is posible to stop derivative evaulation in an expression?


A = f[x]g[x];
F = W[t, n] /. W[x_, n_] -> D[A, {x, n}]

I would like F to be PartD(t, n)(f(t)g(t)) with the derivative not calculated, and when I evaluate

F /. n -> 0

I would like to get the general partial derivative


P.S. Sorry for language mistakes.

  • $\begingroup$ Could just do the usual Leibniz rule: Sum[Binomial[n, k] Derivative[n - k][f][t] Derivative[k][g][t], {k, 0, n}] $\endgroup$ – J. M.'s ennui Oct 18 '18 at 10:09
  • $\begingroup$ A=f[x]*g[x] is simple example. For general case i dont know how A look like. $\endgroup$ – zbyneksmetana Oct 18 '18 at 10:14
  • 2
    $\begingroup$ So you want something like Inactive[D][A, {x, n}]? $\endgroup$ – J. M.'s ennui Oct 18 '18 at 10:16
  • $\begingroup$ Thanks ... maybe it will help. $\endgroup$ – zbyneksmetana Oct 18 '18 at 10:22

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