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MathGroup Archive 2005

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Re: Types in Mathematica, a practical example

  • To: mathgroup at smc.vnet.net
  • Subject: [mg62855] Re: Types in Mathematica, a practical example
  • From: "Steven T. Hatton" <hattons at globalsymmetry.com>
  • Date: Tue, 6 Dec 2005 23:10:31 -0500 (EST)
  • References: <dn22cf$ku4$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Ingolf Dahl wrote:


> I am not allowed to Unset or Clear any part of a list either. Why not?

I should probably look into this more carefully before commenting, but, at
the risk of making an incorrect statement, I will say this.  Lists and
other entities in Mathematica are rewritten upon each evaluation.  You
never really modify an existing expression.  Instead, you modify a copy,
and assign the result to the original symbol.

My explanation is almost certainly an oversimplification in need of
refinement, but I believe it addresses the essence of your question.
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