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MathGroup Archive 2005

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Re: Controlled evaluation of functions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg56808] Re: [mg56763] Controlled evaluation of functions
  • From: Chris Chiasson <chris.chiasson at gmail.com>
  • Date: Fri, 6 May 2005 03:00:50 -0400 (EDT)
  • References: <200505051002.GAA22030@smc.vnet.net>
  • Reply-to: Chris Chiasson <chris.chiasson at gmail.com>
  • Sender: owner-wri-mathgroup at wolfram.com

Use

myrule=k[x_]->x^2

Then whenever you decide to evaluate k, append

/.myrule

to the end of the statement.

On 5/5/05, Brett Patterson <muckle.moose at gmail.com> wrote:
> Consider the following behaviour:
> 
>   In[1]:= f[i_, x_] := Sin[i x]
> 
>   In[2]:= g[x_] = Table[f[i, x], {i, 3}]
> 
>   Out[2]= {Sin[x], Sin[2 x], Sin[3 x]}
> 
>   In[3]:= {3, 0, 1} . g[y]
> 
>   Out[3]= 3 Sin[y] + Sin[3 y]
> 
> This is what I want to do, but using my own function instead of Sin.
> However, this is the result:
> 
>   In[4]:= k[x_] := x^2           (* This is my alternative to Sin *)
> 
>   In[5]:= f[i_, x_] := k[i x]
> 
>   In[6]:= g[x_] = Table[f[i, x], {i, 3}]
> 
>   Out[6]= {x^2, 4 x^2, 9 x^2}    (* I want {k[x], k[2 x], k[3 x]} *)
> 
>   In[7]:= {3, 0, 1} . g[y]
> 
>   Out[7]= 12 y^2                 (* I want 3 k[y] + k[3 y] *)
> 
> How can I get the function k to behave like Sin, so that it is not
> evaluated?
> 
> Note that in my real application, k is a lot more complex and has
> conditions on its arguments, etc.
> 
> Thanks!
> 
> Brett Patterson
> 
> 


-- 
Chris Chiasson
http://chrischiasson.com/
1 (810) 265-3161


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