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MathGroup Archive 1999

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Re: Re: "At long last, Sir, have you no shame?"

  • To: mathgroup at smc.vnet.net
  • Subject: [mg18551] Re: [mg18524] Re: "At long last, Sir, have you no shame?"
  • From: "Kevin J. McCann" <kevinmccann at Home.com>
  • Date: Sat, 10 Jul 1999 02:18:47 -0400
  • References: <7luk6s$l95@smc.vnet.net> <199907090232.WAA29397@smc.vnet.net.>
  • Sender: owner-wri-mathgroup at wolfram.com

I agree, the Mathematica answer is *clearly* nonsense, and for wri to claim
otherwise because "Sum has attribute HoldAll" indicates that that person is
more fascinated with the software than the purpose that the users have for
purchasing it.  I did not purchase Mathematica because of this "feature", rather to
solve problems.  The most insidious thing about such bugs is that they may
not be so obvious in a complex piece of analysis.

Kevin

----- Original Message -----
From: Colin Rose <colin at tri.org.au>
To: mathgroup at smc.vnet.net
Subject: [mg18551] [mg18524] Re: "At long last, Sir, have you no shame?"


>
> David Withoff <withoff at wolfram.com> wrote:
>
>
> > independent experts often disagree about what is or is not a bug.
>
>
>
> Two cases instantly come to mind:
>
>
> 1.   Sum in v4
>      _________
>
> Consider say:
>
>     In[1]:=     g = Exp[-i];
>
>
>     In[2]:=     Sum[g, {i, 1, n}]
>
>     Out[2]=     n/E^i
>
> which is nonsense. This happens for almost ANY expression g=g(i).
> To get the correct answer, you have to wrap Evaluate around g:
>
>    In[3]:=      Sum[Evaluate[g], {i, 1, n}]
>    Out[3]=      (-1 + E^n)/(E^n*(-1 + E))
>
> Wolfram support says Out[2] is not a bug, since Sum has attribute HoldAll.
> I say it is clearly (and obviously) an extremely serious bug,
> in the sense that it gives the wrong answer to almost any Summation
> where g is pre-defined. I reported  it under v4 alpha, it was fixed
> in the betas, and it is now back in the v4 final release. But then
> it isn't a bug, apparently !?
>
>




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