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Re: Re: Making parts of formulae blinking

  • To: mathgroup at smc.vnet.net
  • Subject: [mg91277] Re: Re: Making parts of formulae blinking
  • From: Alexei Boulbitch <Alexei.Boulbitch at iee.lu>
  • Date: Wed, 13 Aug 2008 04:39:31 -0400 (EDT)

Dear David,

thank you for your helpful comment. I agree that it is an important problem, especially if 
one wants to use Mathematica for giving talks on subjects of general interest, rather than 
only on Mathematica itself. The question we discuss is thus, in no case a "disposable" one.
 
You are right, it is much easier, if one can avoid going to graphics, and I like your approach much. 

However, I still have an unsolved question concerning using the operator Accentuate[].

In my previous letter for the sake of shortness I have given an oversimplified 
expression AB+xy. The procedure "Accentuate" works perfectly on it. In reality however, one often 
needs to accentuate parts of an expression that have different lengths. Further, often there are more than two 
parts of the same expression that should be accentuated separately. In this case a straightforward use 
of the operator Accentuate results in a change of the order of the parts of the expression. 

For example, I need to discuss four parts of the same expression. They should be discussed separately 
from one another. Here they are: 

a1 = Text[Style["\!\(\*SuperscriptBox[\"\[Alpha]\[Eta]\", 
RowBox[{\"  \", \"2\"}]]\)+\!\(\*SuperscriptBox[\"\[Beta]\[Eta]\", 
RowBox[{\"  \", \"4\"}]]\)", FontFamily -> "Times New Roman", 22, 
   Italic]]

a2 = Text[
  Style["g(\[CapitalDelta]\[Eta]\!\(\*SuperscriptBox[\")\", \
\"2\"]\)", FontFamily -> "Times New Roman", 22, Italic]]

a3 = Text[
  Style["\!\(\*FractionBox[\"1\", \"2\"]\)\!\(\*SubscriptBox[\"C\", \
\"ijkl\"]\)\!\(\*SubscriptBox[\"\[Epsilon]\", \
\"ij\"]\)\!\(\*SubscriptBox[\"\[Epsilon]\", \"kl\"]\)", 
   FontFamily -> "Times New Roman", 22, Italic]]

a4 = Text[Style["\!\(\*SuperscriptBox[\"A\[Eta]\", 
RowBox[{\"  \", \"2\"}]]\)\!\(\*SubscriptBox[\"\[Epsilon]\", \
\"ii\"]\)", "Times New Roman", 22, Italic]]

These illustrate a problem from the area of phase transitions. 

Applying the operator Accentuate to these parts in a direct way:

expression=Accentuate[a1]+Accentuate[a2]+Accentuate[a3]+Accentuate[a4]

or like this 
a1  + a2 +  a3 + a4;
Accentuate /@ %

I get a nicely working output, but no control on the order in which the parts appear. This may make 
my message obscure to the audience and therefore, should be changed. 

Could you give a hint of how this problem could be fixed?

Best regards, Alexei


Alexei,

This is a very interesting question because in the larger sense it relates 
to how one manipulates expressions and presents concepts, in a clear and 
elegant manner, to a reader of a notebook. I think this is somewhat an open 
question and we have to learn how to do it. So my answer is not going to be 
totally responsive and I think that your first approach is not the best 
because it draws you off into computer science and away from the math and 
physics. Also, a blinking graphical display may serve a tutorial purpose but 
it is a dead-end expression that can't be further used. (Also I don't know 
right off how to get some blinking in, but I'm certain some member of 
MathGroup will do it.)

So instead of going to graphics, which in general might be quite complicated 
to get all the formatting correct, let's try to stay with regular 
expressions that can be accentuated with EventHandlers and then returned 
again to regular expressions. Here are two routines to help do that:

Accentuate[expr_] :=
 Module[{col = Black, size = Medium},
  EventHandler[
   Style[expr, FontColor -> Dynamic[col],
    FontSize ->
     Dynamic[size]], {"MouseClicked" :> (col =
       col /. {Black -> Red, Red -> Black};
      size = size /. {Large -> Medium, Medium -> Large})}]]

ClearAccentuate[expr_] :=
 expr /. HoldPattern[EventHandler[Style[subexpr_, __], __]] -> subexpr

Now we can use these on your example and then return to a normal expression. 
Or we could have just saved the initial expression. In any case, we don't 
have to go to graphics.

A B + x y
Accentuate /@ %
% // ClearAccentuate // InputForm

-- 
Alexei Boulbitch, Dr., Habil.
Senior Scientist

IEE S.A.
ZAE Weiergewan
11, rue Edmond Reuter
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Luxembourg

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