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MathGroup Archive 1999

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

  • To: mathgroup at smc.vnet.net
  • Subject: [mg18604] Re: [mg18551] Re: [mg18524] Re: "At long last, Sir, have you no shame?"
  • From: "Andrzej Kozlowski" <andrzej at tuins.ac.jp>
  • Date: Tue, 13 Jul 1999 01:01:31 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

Note the following.

In[1]:=
g = Exp[-i];

In[2]:=
Sum[g, {i, 1, n}]
Out[2]=
n
--
 i
E

In[3]:=
Product[g, {i, 1, n}]
Out[3]=
 -(1/2) n (1 + n)
E

In[4]:=
Attributes[Sum]
Out[5]=
{HoldAll, Protected, ReadProtected}

In[5]:=
Attributes[Product]
Out[6]=
{HoldAll, Protected, ReadProtected}



--
Andrzej Kozlowski
Toyama International University
JAPAN
http://sigma.tuins.ac.jp
http://eri2.tuins.ac.jp


----------
>From: "Kevin J. McCann" <kevinmccann at Home.com>
To: mathgroup at smc.vnet.net
>To: mathgroup at smc.vnet.net
>Subject: [mg18604] [mg18551] Re: [mg18524] Re: "At long last, Sir, have you no shame?"
>Date: Sat, Jul 10, 1999, 3:18 PM
>

> 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
> To: mathgroup at smc.vnet.net
> Subject: [mg18604] [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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