       Re: Matrices with square brackets

• To: mathgroup at smc.vnet.net
• Subject: [mg102625] Re: Matrices with square brackets
• From: cca at gregosetroianos.mat.br
• Date: Mon, 17 Aug 2009 04:03:47 -0400 (EDT)

```George Woodrow III wrote:

Thank you for your response. However, the question is: how to use matrices
delimited by square brackets. MatrixForm and TraditionalForm return
matrices with round brackets (parentheses).

The problem, of course, is that square brackets in Mathematica are reserved
to functional aplication. Even so, it is possible to teach the system how
to parse matrices with square brackets and how to output matrices in the
same format. For \$VersionNumber<=6, I have done this using \$PreRead,
\$PrePrint and box programming. (Almost anything is possible with boxes!)
For \$VersionNumber>=7, here is an example of what I meant. (Below I use the
new typesetting function TemplateBox.)

NotebookWrite[InputNotebook[],
TemplateBox[{GridBox[{{"a", "b"}, {"c", "d"}}]}, "Identity",
DisplayFunction -> (RowBox[{StyleBox["[", SpanMaxSize -> \[Infinity]], #1,
StyleBox["]", SpanMaxSize -> \[Infinity]]}] &)]]

This pastes a matrix with square brackets that can be used normally (as you
would do with determinants with vertical bars in Mathematica since older
versions). You cand add rows or columns without destroying the hidden box
structure. You can copy, paste and evaluate to try other things. Given this
box representation, now its is easy to make the system output matrices with
square brackets (in StandardForm or TraditionalForm). You can also create a
dialog box with input fields to paste such matrices with any dimensions.

My concern here is that this solution, although easy for me, could be much
simpler. I myself prefer matrices with parentheses, but many pre-college
teachers in my country do not.

Carlos Cesar de Araujo
Gregos & Troianos Educacional
www.gregosetroianos.mat.br
Belo Horizonte, MG, Brasil
(31) 3283-1122

```

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