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Re: unexpected behaviour of Sum

  • To: mathgroup at
  • Subject: [mg126573] Re: unexpected behaviour of Sum
  • From: Murray Eisenberg <murray at>
  • Date: Sat, 19 May 2012 05:49:01 -0400 (EDT)
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  • References: <joq5h8$r20$> <jot5hm$am0$> <>
  • Reply-to: murray at

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On 5/18/12 5:22 AM, perplexed wrote:
> Thanks to everybody.
> It is surely true I could write a better definition
> for my functions (sod was just an example),
> but still I do think that this is an imperfection in
> the documentation of Sum.
> First of all, this SymbolicSumThreshold option
> is never cited in the documentation of Sum.
> In general, there is never a hint to the fact that
> Sum will try to sum symbolically in the case of
> a definite sum. If I did know, I would have considered
> writing a better function.
> On the contrary, in the documentation of Sum I read :
> "If the range of a sum is finite, i is typically assigned a sequence
> of values,
> with f being evaluated for each one."
> and
> "If a sum cannot be carried out explicitly by adding up a finite
> number of terms,
> Sum will attempt to find a symbolic result. In this case, f is first
> evaluated symbolically."
> With due respect,
> I think that maybe a couple of lines should be added to the
> documentation at least in the "Possible issues" section.

Murray Eisenberg                     murray at
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305

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