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MathGroup Archive 2004

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Telling Mathematica that a symbol is going to be a List?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg50817] Telling Mathematica that a symbol is going to be a List?
  • From: AES/newspost <siegman at stanford.edu>
  • Date: Wed, 22 Sep 2004 00:11:55 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

I want to define a function containing parameters that are going to be 
elements in a list, e.g. something like

  m := { { d[[1]], 0, 0}, {0, d[[2]], 0}, {0, 0, d[[3]]}

but not define the list of values of  d  until later (and not put the 
parameters in as explicit arguments of  m  just to keep the appearance 
less cluttered and typing easier).

If I then give an input line

    m /. {d -> {d1, d2, d3} } // MatrixForm

I get "Part::partd" errors -- but the matrix then displays correctly.

I can of course just Off[] the errors -- but is there a better way.


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