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MathGroup Archive 1999

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Re: Need a means to get arguments of a function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg18514] Re: [mg18444] Need a means to get arguments of a function
  • From: "Andrzej Kozlowski" <andrzej at tuins.ac.jp>
  • Date: Thu, 8 Jul 1999 22:32:52 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

I think you should explain more clearly what exactly you want to do.

You can get the original arguments of w in held form by using

In[2]:=
HeldPart[w, 3]
Out[2]=
Hold[v]

However this may not be the most convenient approach for your purpose. If
you just  want to demonstrate the chain rule in this case, what's wrong with
the following:

In[3]:=
D[f[x, u, h[x, y]], y]
Out[3]=
 (0,1)        (0,0,1)
h     [x, y] f       [x, u, h[x, y]]

and so on?
--
Andrzej Kozlowski
Toyama International University
JAPAN
http://sigma.tuins.ac.jp
http://eri2.tuins.ac.jp


----------
>From: Patrick Reany <reany at xroads.com>
To: mathgroup at smc.vnet.net
>To: mathgroup at smc.vnet.net
>Subject: [mg18514] [mg18444] Need a means to get arguments of a function
>Date: Wed, Jul 7, 1999, 1:11 PM
>

> I'm using version 3.0.1 to demonstrate the differentiation of composite
> functions. I need a means to get arguments to user-defined function(s)
> to demonstrate the chain rule. For example, if the user put in
>
> w = f[x,u,v] and v = h[x,y]
>
> I need to get at each of the arguments of  f, even though Mathematica
> wants to substitute out v in f by h[x,y].
>
> Does Mathematica allow me to get at the original number of arguments of
> f and does it have an indexed function that lets me get at each
> particular argument of  f, such as allowing me to determine, say, that
> the third argument of  f is v?
>
> Thanks
>
> Patrick
> 


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