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Re: Use of delayed assignment, :=, with a list

  • To: mathgroup at
  • Subject: [mg91827] Re: Use of delayed assignment, :=, with a list
  • From: Bill Rowe <readnews at>
  • Date: Tue, 9 Sep 2008 06:57:40 -0400 (EDT)

On 9/7/08 at 10:53 PM, PHILLMAN5 at (phillman5) wrote:

>On Sep 7, 3:34 am, phillman5 <PHILLM... at> wrote:
>Some pointed out that the above works.  I entered my question using
>the braces for ease of entering.   If there are several matrixes,
>entering the result for the rhs would get unweilding.  Using the
>matrix form from the input pallet still does not seem to work.

The issue isn't whether the matrices are entered using the
palette or with braces. That is,

{{a, b}, {c, d}} := {{1, 0}, {-1/f, 1}}.{{1, zomeasure}, {0, 1}}

will generate the same error you reported.

The issue is the rhs is a matrix product which does not get
evaluated since you are using SetDelayed. You can make this work
by forcing the matrix product to be evaluated. That is,

{{a, b}, {c, d}} := Evaluate[{{1, 0}, {-1/f, 1}}.{{1,
zomeasure}, {0, 1}}]

works regardless of whether you choose to enter the matrices
with the palette or not.

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