Re: "Alternating" function

*To*: mathgroup at smc.vnet.net*Subject*: [mg63267] Re: [mg63260] "Alternating" function*From*: ggroup at sarj.ca*Date*: Thu, 22 Dec 2005 00:04:29 -0500 (EST)*References*: <200512210435.XAA14743@smc.vnet.net>*Reply-to*: ggroup at sarj.ca*Sender*: owner-wri-mathgroup at wolfram.com

On Tuesday, December 20, 2005 at 23:35 GMT -0500, Renan wrote: > 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") You could define a dummy index variable at the beginning of your cell (eg. i=1;). Then in your function, simply add the factor ((-1)^i++). That way i is incremented every time the function is applied.

**References**:**"Alternating" function***From:*Renan <renan.birck@gmail.com>