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MathGroup Archive 2004

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Re: Pattern matching partial derivatives

  • To: mathgroup at smc.vnet.net
  • Subject: [mg52409] Re: Pattern matching partial derivatives
  • From: David Bailey <dave at Remove_Thisdbailey.co.uk>
  • Date: Fri, 26 Nov 2004 01:04:39 -0500 (EST)
  • References: <co4dsi$l82$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Nicolas Girard wrote:
> Hi all,
> I can't get finding patterns that would match a simple partial derivative:
> 
> Input:
>   ?f
>   ?x
>   D[f, x, NonConstants -> {f}] // FullForm
> 
> Output:
>   Global`f
>   Global`x
>   D[f, x, Rule[NonConstants, List[f]]]
> 
> Input:
>   MatchQ[
>     D[f, x, Rule[NonConstants, List[f]]],
>     D[f_, x_, Rule[NonConstants, nc_]]
>   ]
> Output:
>   False
> 
> 
> Am I damned ?
> Many thanks in advance !
> Cheers,
> Nicolas
> 
Nicolas,

Yes, getting this output from Mathematica can be a sign of damnation!

Alternatively, look at this:

D[f_, x_, Rule[NonConstants, nc_]] // FullForm

0

If you want to manipulate derivatives in complicated ways, one way is to 
use your own notation for a derivative (say dD) which will obviously not 
evaluate, and then use dD ->D to get evaluation when you need it.

David


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