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MathGroup Archive 1999

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Re: BracketingBar for output

  • To: mathgroup at smc.vnet.net
  • Subject: [mg15812] Re: BracketingBar for output
  • From: Paul Abbott <paul at physics.uwa.edu.au>
  • Date: Mon, 8 Feb 1999 03:25:39 -0500 (EST)
  • Organization: University of Western Australia
  • References: <79e86b$96l@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Peter Breitfeld wrote:

> In my "personal package" I have the function Betrag[x_]:=Sqrt[x.x]
> 
> Now I want that in cases where this function can't be evaluated, the
> output in StandardForm is displayes as |x|. (left and right
> BracketingBar, these symbols you get when entering `ESC l| ESC' and
> `ESC r| ESC'.

Actually, to indicate such a norm I would use DoubleBracketingBar
instead of BracketingBar:

In[1]:= DoubleBracketingBar[(x_)?VectorQ]:= Sqrt[x . x]

In[2]:= DoubleBracketingBar[{a,b,c}] Out[2]=
      2    2    2
Sqrt[a  + b  + c ]

Then there is no need to define Betrag.

Here are these input lines in TraditionalForm -- which is much more
readable:

Notebook[{
Cell[BoxData[
    \(TraditionalForm
    \`\[LeftDoubleBracketingBar]x_?VectorQ\[RightDoubleBracketingBar] :=

      \ at \(x . x\)\)], "Input"],

Cell[CellGroupData[{

Cell[BoxData[
    \(TraditionalForm
    \`\[LeftDoubleBracketingBar]{a, b, c}\[RightDoubleBracketingBar]\)],

  "Input"],

Cell[BoxData[
    \(TraditionalForm\`\ at \(a\^2 + b\^2 + c\^2\)\)], "Output"] }, Open 
]],

Cell[CellGroupData[{

Cell[BoxData[
    \(TraditionalForm
    \`\[LeftDoubleBracketingBar]x\[RightDoubleBracketingBar]\)],
"Input"],

Cell[BoxData[
    \(TraditionalForm
    \`\[LeftDoubleBracketingBar]x\[RightDoubleBracketingBar]\)],
"Output"]
}, Open  ]]
}
]

Cheers,
	Paul

____________________________________________________________________ 
Paul Abbott                                   Phone: +61-8-9380-2734
Department of Physics                           Fax: +61-8-9380-1014
The University of Western Australia            Nedlands WA  6907       
mailto:paul at physics.uwa.edu.au  AUSTRALIA                       
http://www.physics.uwa.edu.au/~paul

            God IS a weakly left-handed dice player
____________________________________________________________________


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