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MathGroup Archive 2005

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Re: "Alternating" function

  • To: mathgroup at
  • Subject: [mg63275] Re: [mg63260] "Alternating" function
  • From: "David Park" <djmp at>
  • Date: Thu, 22 Dec 2005 00:04:36 -0500 (EST)
  • Sender: owner-wri-mathgroup at


What about using Fold?

Fold[x + #2*f[#1] & , x, Table[(-1)^i, {i, 5}]]
x - f[x + f[x - f[x + f[x - f[x]]]]]

David Park
djmp at

From: Renan [mailto:renan.birck at]
To: mathgroup at


I want to make a "nested function" like: 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.


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