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MathGroup Archive 2005

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Re: Two related question. Question 1

  • To: mathgroup at smc.vnet.net
  • Subject: [mg57538] Re: Two related question. Question 1
  • From: David Bailey <dave at Remove_Thisdbailey.co.uk>
  • Date: Tue, 31 May 2005 05:00:41 -0400 (EDT)
  • References: <d7dp2r$qam$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Kazimir wrote:
> I have two related question. Let me introduce a pure function
> 
> f = #1^2 + #2 &
> 
> Now. I want to make an operation over the function, for example to
> find its square and to call the result (the expected function f = (#1^2
> + #2)^2 & ) c:
> 
> c=f^2
> 
> However, I do not obtain this, as 
> 
> c[a,b]
> 
> does not evaluate to (a+b)^2. Can anybody advise me how to obtain
> such a function without long substitutions. I would like to obtain
> something which is made for derivatives :
> 
> In[11]:=
> Derivative[1][f]
> 
> Out[11]=
> 2 #1&
> 
> In[12]:=
> Derivative[2][f]
> 
> Out[12]=
> 2&
> 
> Regards 
> 
> Vlad
> 
Vlad,

Look at your pure function in FullForm, and the answer is more or less 
obvious:

Function[Plus[Power[Slot[1],2],Slot[2]]]

For example:

g=With[{ff=f[[1]]^2},Function[ff]]

Note however that Function can have several arguments, which would 
require some more general code.

David Bailey
http://www.dbaileyconsultancy.co.uk


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