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MathGroup Archive 2006

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Re: Problem with derivate of product

  • To: mathgroup at smc.vnet.net
  • Subject: [mg67337] Re: [mg67309] Problem with derivate of product
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Sun, 18 Jun 2006 05:13:48 -0400 (EDT)
  • References: <200606170836.EAA28052@smc.vnet.net> <83AE65A6-9C96-4721-90EA-F5D1FE82ADAA@mimuw.edu.pl> <Pine.OSF.4.58.0606180338590.137680@sirppi.helsinki.fi> <C136A310-FECA-43D9-9A76-64D1B0E0E008@mimuw.edu.pl>
  • Sender: owner-wri-mathgroup at wolfram.com

On 18 Jun 2006, at 10:23, Andrzej Kozlowski wrote:

>
> On 18 Jun 2006, at 09:49, Esa A E Peuha wrote:
>
>> On Sat, 17 Jun 2006, Andrzej Kozlowski wrote:
>>
>>> On 17 Jun 2006, at 17:36, Esa A E Peuha wrote:
>>>
>>>> Mathematica 5.0 seems to have trouble with parsing this input:
>>>>
>>>> In[1]:= D[Product[f[k,z],{k,0,m}],{z,n}]
>>>>
>>>> Out[1]= D[Product[f[k, z], {k, 0, m}], z]
>>>>
>>>> Has this been fixed in newer versions?
>>>>
>>>> --
>>>> Esa Peuha
>>>> student of mathematics at the University of Helsinki
>>>> http://www.helsinki.fi/~peuha/
>>>>
>>>
>>> No. Also, I do not think there is any plan to "fix it" because it is
>>> not considered to be "broken".
>>
>> Do you mean that the change from "{z,n}" to "z" is what should happen
>> in this case?  (No, n has not been set equal to 1.)
>>
>
> No, I misunderstood you (sorry) by not looking carefully at the  
> output. Nothing should happen but something does, which indeed  
> looks like a very weird bug.
>
> Andrzej Kozlowski

No doubt this is indeed a bug and it is not fixed in v. 5.1,  but on  
the other hand, if you really need it for something (I am curious  
what it might be) the following should work equally well:


Dt[Product[f[k, z], {k, 0, m}], {z, n}]


Dt[Product[f[k, z], {k, 0, m}], {z, n}]


Andrzej Kozlowski


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