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Re: Replacing Parts of a List

  • To: mathgroup at smc.vnet.net
  • Subject: [mg28757] Re: [mg28742] Replacing Parts of a List
  • From: Andrzej Kozlowski <andrzej at tuins.ac.jp>
  • Date: Fri, 11 May 2001 20:00:35 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

I am not sure if I understand you correctly. The way I see it the situation
is exactly the same with Subscript as it is with List. Compare:

 In[1]:=
l={a,b};l[[2]]=3;l

Out[1]=
{a, 3}

In[2]:=
Clear[l]

In[3]:=
l=Subscript[a,b];l[[2]]=3;l

Out[3]=
a
 3

Same behaviour. Equally,  neither {a, b}[[2]] = 3 nor Subscript[a,b][[2]]=3
will work and for the same reason.

Perhaps I have missed your point? Could you be more explicit?

-- 
Andrzej Kozlowski
Toyama International University
JAPAN

http://platon.c.u-tokyo.ac.jp/andrzej/
http://sigma.tuins.ac.jp/~andrzej/


on 01.5.11 4:38 PM, Roger Jones at rmj at SLAC.Stanford.EDU wrote:

> Given x={1,2} then setting part 1 to 10 (say) is done via x[[1]]=10.
> This
> appealing as it is a condensed notation and is  I believe, very
> efficient for large
> arrays.
> 
> However, with a subscripted symbol  (such as Subscript[x,y]) how is it
> done?
> 
> It can be achieved with Subscript[x,y]=ReplacePart[Subscript[x,y],10,1]
> but this is a little unwieldy.
> 
> Is there some method (using Hold[Subscript[x,y]] or something like this)
> 
> that allows a direct replacement?
> 
> Thank you!
> 
> -Roger Jones
> 
> 
> 
> 
> 




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