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MathGroup Archive 1999

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RE: Automatic Display in MatrixForm

  • To: mathgroup at smc.vnet.net
  • Subject: [mg19542] RE: Automatic Display in MatrixForm
  • From: "Ersek, Ted R" <ErsekTR at navair.navy.mil>
  • Date: Tue, 31 Aug 1999 00:52:28 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

Colin Rose wrote:
-----------------------------

A few weeks ago, there was much excitement here when it was shown that one
can get all the advantages of MatrixForm output, without the disadavantages
.....

Now suppose:

  1) We switch the above ON.
  2) Then, how do we switch it off for a particular function's ouptut.

That is, if MyFunc[x] returns a matrix, which we want formatted
as a List (and not in "Fancy Matrix" form), how can we switch
it off LOCALLY for this function's output only,
and without converting back to InputForm ?


------------------------------
REPLY:
The code below should do the trick.  Notice I am using my latest version
here which doesn't display the result from Solve or an empty matrix with
'MatrixForm'.

For those who may be puzzled the (HiddenSymbols`) context is something I
dreamed up.

-------------------------------

In[1]:=
$Pre:=(HiddenSymbols`UseMatrixForm=True;#&)

In[2]:=
MakeBoxes[m_?(Function[t,MatrixQ[Unevaluated[t]] && 
 Flatten[t//.{_Rule->Sequence[],_RuleDelayed->Sequence[]}]=!={},
 HoldAll ]), StandardForm]/;HiddenSymbols`UseMatrixForm :=
  RowBox[{"(", GridBox[Map[Function[t,MakeBoxes[t,StandardForm],HoldAll],
          Unevaluated[m],{2}]],")"}]

In[3]:=
MyFunc[x_]:=(HiddenSymbols`UseMatrixForm=False;3 x)

In[4]:=
m={{1,2,1},{1,0,1},{0,0,1}}
MyFunc[m]
m.m


Out[4]=
  1  2  1
  1  0  1
  0  0  1


Out[5]=
  {{3,6,3},{3,0,3},{0,0,3}}


Out[6]=
  3  2  4
  1  2  2
  0  0  1


--------------------

Isn't that delicious.
Ted Ersek

For Mathematica tips, tricks see 
http://www.dot.net.au/~elisha/ersek/Tricks.html



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