Pattern matching a multivariate derivative

Question

I can extract the parameters of a single variable derivative with the rule

D[f[x], x] /. Derivative[order_][fcn_][variable_] ->
  {order, fcn, variable}

produces

{1, f, x}

How do I generalize this to the multivariate case? For example,

D[f[x, y], x, y] /. Derivative[order_][fcn_][variable_] ->
  {order, fcn, variable}

produces

The match didn't work -- but I can't seem to reproduce the actual Mathematica display.

I'm sure there's some magic syntax that will accomplish the match. I tried a few variations to no avail. Can anyone help?

Thanks much.

Answer 1

You have to look at the FullForm or InputForm to see, how you can match your expression.

InputForm[D[f[x, y], x, y]]

(*
  Derivative[1, 1][f][x, y]
*)

The order in your second example is a sequence of numbers. The same is true for the variables you try to match. Therefore you have to use BlankSequence in your pattern

D[f[x, y], x, y] /. 
 Derivative[order__][fcn_][variable__] -> {{order}, fcn, {variable}}

(*
  {{1, 1}, f, {x, y}}
*)