Re: combinations of pure functions
- To: mathgroup at smc.vnet.net
- Subject: [mg16598] Re: [mg16532] combinations of pure functions
- From: Andrzej Kozlowski <andrzej at tuins.ac.jp>
- Date: Wed, 17 Mar 1999 23:55:05 -0500
- Sender: owner-wri-mathgroup at wolfram.com
Gianluca:
Just one more adition to my previous answer to your question. If for some
reason you do not like to add new global rules you can of course do this:
In[1]:=
op = Identity - (D[#,x]&)
Out[1]=
Identity - (D[#1, x] & )
In[2]:=
Through[op[x^2],Plus]/.(-f_)[x_]->-(f[x])
Out[2]=
2
-2 x + x
Andrzej
On Tue, Mar 16, 1999, Gianluca Gorni <gorni at dimi.uniud.it> wrote:
>Hello!
>
>Talking of operators, consider the example of the Book
>at Section 2.2.9:
>
> op = Identity + (D[#,x]&)
>
>To find the value of op on the expression x^2 it is
>suggested to use Through:
>
> Through[op[x^2], Plus]
>
>Unfortunately the suggestion fails if we just change +
>into - in op:
>
> op2 = Identity - (D[#,x]&)
>
>What can one do? I have thought of a replacement rule:
>
> op2 /. {Identity -> x^2, f_Function -> f[x^2] }
>
>Anyone has a better idea?
>
>Thank you in advance,
>
> Gianluca Gorni
>
>
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>
>
Andrzej Kozlowski
Toyama International University
JAPAN
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