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MathGroup Archive 2005

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Re: "Alternating" function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg63271] Re: [mg63260] "Alternating" function
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Thu, 22 Dec 2005 00:04:33 -0500 (EST)
  • Reply-to: hanlonr at cox.net
  • Sender: owner-wri-mathgroup at wolfram.com

expr=x+f[x-f[x+f[x-f[x+f[x]]]]];

expr==Module[{n=1},
    Nest[x-(-1)^n++*f[#]&, x, 5]]

True

expr==Module[{n=1},
    Nest[x-Cos[Pi*n++]*f[#]&, x, 5]]

True


Bob Hanlon

> 
> From: Renan <renan.birck at gmail.com>
To: mathgroup at smc.vnet.net
> Date: 2005/12/20 Tue PM 11:35:44 EST
> Subject: [mg63271] [mg63260] "Alternating" function
> 
> Hello,
> 
> I want to make a "nested function" like: x + f[x - f[x + f[x - f[x + f[x]]]]].
> 
> I've tried using Nest but I don't find how to keep switching between
> Plus and Minus: I would need something that would return an "index" so
> I could keep track of when I need to "switch" the operation. (e.g. if
> the "index" is odd, the operation is "Plus", otherwise is "Minus")
> 
> How can I make this? I looked in the help but didn't find any informations.
> 
> Thanks.
> 
> 
> 
> 
> --
> Thanks/obrigado, Renan "Wishmaster" Birck - Canoas, Rio Grande do Sul, Brasil
> MSN: wizard_of_yendor at hotmail.com
> Orkut: http://www.orkut.com/Profile.aspx?uid=2202360379963855296
> 
> 


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