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Re: how uncouple dynamic objects?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg109444] Re: how uncouple dynamic objects?
  • From: Albert Retey <awnl at gmx-topmail.de>
  • Date: Tue, 27 Apr 2010 07:41:06 -0400 (EDT)
  • References: <hr65qt$jp8$1@smc.vnet.net>

Am 27.04.2010 10:04, schrieb Murray Eisenberg:
> Here's a simple example of a more complicated situation where I define a
> function that takes a function as argument and uses Manipulate to
> produce its output:
> 
>    fplot[f_]:= Manipulate[
>                  Plot[f[x+a],{x,-2,2}],
>                {a,0,2}]
>    f[x_]:= x^2
>    fplot[f]
> 
>    f[x_]:=x^3
>    fplot[f]
> 
> When I execute the second definition (with x^3) of f, it automatically
> changes the f used in the still-displayed output from the first call to 
> fplot.
> 
> How can I isolate the two instances -- and yet still use the same name
> for the two different functions?  (Or is this not possible?)

Manipulate knows the TrackedSymbols-Option, if you put in everything
that needs to be tracked except for f it will behave as you require:

fplot[f_] :=
 Manipulate[Plot[f[x + a], {x, -2, 2}], {a, 0, 2},
  TrackedSymbols :> {a}]


It will isolate in the sense that the Manipulate just doesn't realize it
is still using an old definition of f. I can't say whether that will
cause problems or will isolate the two definition in every situation but
for your example it seems to work...

> Clearly this is an issue of the dynamic structure underlying
> Manipulate, and I'm willing to use a "direct" definition using a
> Dynmaic variable a with a control instead of the simpler
> Manipulate. But of course I'd prefer to be able to do it with
> Manipulate.
> 

hth,

albert


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