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MathGroup Archive 2000

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Re: Set in Scan

  • To: mathgroup at smc.vnet.net
  • Subject: [mg21924] Re: [mg21856] Set in Scan
  • From: "Tomas Garza" <tgarza at mail.internet.com.mx>
  • Date: Fri, 4 Feb 2000 02:54:51 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Johannes Ludsteck [ludsteck at zew.de] wrote:

> I have to do replacements in very long lists. An efficient way to do 
> this is to use
> 
> x[[index]]=newElement.
> 
> This, however, doesn't work if I want to do replacements for a set of 
> lists. If I try to replace the third element in the lists v1, v2 
> and v3 by 
> typing
> 
> Scan[#[[3]] = newElement &, {v1,v2,v3}]
> I get the error message
> Set::setps: #1 in assignment of part is not a symbol.
> 
> Any suggestions?

I suggest you use ReplacePart instead of direct assignment:

In[1]:=
g[x_]:= ReplacePart[x,newElement,3]

and then Map this function on the list {v1, v2, v3} thus:

In[2]:=
g[#]&/@{v1,v2,v3}

This works fine.

Tomas Garza
Mexico City


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