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Re: Caution! Reuse of variables within Manipulate

  • To: mathgroup at smc.vnet.net
  • Subject: [mg89064] Re: Caution! Reuse of variables within Manipulate
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Sun, 25 May 2008 03:19:16 -0400 (EDT)
  • References: <g18hts$kkp$1@smc.vnet.net>

Hi,

 > Is this surprising, or has this been mentioned in the Documentation?

AFAIK it is not mentioned in the Documentation, that you are surprised.

Regards
   Jens

Frank Iannarilli wrote:
> Hi,
> 
> 
> Here's a cautionary note about (re)use of dynamic variables inside
> Manipulate[].
> 
> To wit, here's code to demonstrate the issue.  Note the reuse of the
> variable d, and Pause[]:
> 
> Manipulate[
> d = b;
> Pause[1.];
> d = Max[Sin[b], Sin[a]];
> Plot[a Sin[b t], {t, 0, 10}, PlotRange -> {All, {-10, 10}}],
> {{a, 1, "a"}, 0, 10, Appearance -> "Labeled"},
> {{b, 1, "b"}, 0, 10, Appearance -> "Labeled"},
> Item[Row[{Style["Goofy: ", Blue], Dynamic[d]}, Spacer[2]],
>   Alignment -> Left]
> ]
> 
> As one plays with the controls, the display of Dynamic[d] (labeled by
> "Goofy") will flicker, showing that indeed the variable d is dynamic
> *every point through* the body of Manipulate.  I had naively assumed
> that one's code within Manipulate would run through from top to bottom
> before the display would be updated.
> 
> Is this surprising, or has this been mentioned in the Documentation?
> 
> Regards,
> Frank
> 


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