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Re: list mutability (very basic question)

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• Subject: [mg131709] Re: list mutability (very basic question)
• From: Alan G Isaac <alan.isaac at gmail.com>
• Date: Sun, 22 Sep 2013 02:47:01 -0400 (EDT)
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On 9/21/2013 10:15 AM, Bob Hanlon wrote:
 > Attributes[Set]
 > {HoldFirst, Protected, SequenceHold}


Thanks, but I'm still unclear:
why does ``{0}[[1]]=1`` raise an error?

As a point of reference for my confusion,
Python behaves in a way I find more intuitive:
``[0,1][1]=0`` does not raise an error.
(This becomes an interesting difference when
we get to argument passing in Mathematica, where HoldFirst
becomes useful as a way to allow "in place" modification.)

Back to Mathematica, am I understanding correctly that after
``Set[Part[x,1],1])`` that x still references the
same location in memory?  How can I easily see that?
(E.g., in Python, I would us the ``id`` function.)

Thanks,
Alan Isaac

• Follow-Ups:
  • Re: list mutability (very basic question)
    • From: Murray Eisenberg <murray@math.umass.edu>

• References:
  • list mutability (very basic question)
    • From: Alan <alan.isaac@gmail.com>