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RE: alternating sums

  • To: mathgroup <mathgroup at christensen.Cybernetics.NET>
  • Subject: [mg313] RE: [mg307] alternating sums
  • From: "Thomson, Peter" <PeterT at>
  • Date: Mon, 12 Dec 94 15:41:00 PST

Re:  [mg307] alternating sums
Jack Golberg writes:

> Here's an elementary question that has me partially stumped.  I often
> have occasion to convert  mylist = {a1,a2,a3,...} into an alternating sum,
> a1-a2+a3-a4+... . I find it aesthetically unsatisfactory to generate a
> list of alternating plus and minus ones, multiply mylist with the
> alternating list and then Apply Plus to the product. ...

where A is the array list, and 2n is the number of terms in the sum.

Peter Thomson

Biometry Unit                 Tel: +61-2-351-2535
Department of Crop Sciences        Fax: +61-2-351-4172
University of Sydney  NSW  2006         e-mail: petert at

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