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MathGroup Archive 2006

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Re: Problem with derivate of product

  • To: mathgroup at smc.vnet.net
  • Subject: [mg67338] Re: [mg67309] Problem with derivate of product
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Sun, 18 Jun 2006 05:13:50 -0400 (EDT)
  • References: <200606170836.EAA28052@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

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". Mathematica does not transform in any  
way products or sums with symbolic limits unless it can evaluate them  
in "closed form" (which obviously it can't in the case of an unknown  
function f). The reason why it does not do so is , I think, due to  
the following "basic principle of computer algebra systems": never  
implement anything which cannot be done better "by hand", or if it is  
only going to be useful in a few very special situations.

Andrzej Kozlowski



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