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MathGroup Archive 2006

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Re: ExpandAll[(a + b) ** c] ?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg71171] Re: [mg71097] ExpandAll[(a + b) ** c] ?
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Thu, 9 Nov 2006 03:40:39 -0500 (EST)
  • References: <200611081115.GAA22416@smc.vnet.net>


On 8 Nov 2006, at 20:15, Christoph Lhotka wrote:

> Hello Mathgroup!
>
> Ho do I make the non-commutative operator ** distributiv with  
> respect to +,
> thus the expression "ExpandAll[(a + b) ** c]" evaluates to "a**c +  
> b**c", by
> setting appropiate attributes to ** and + ?
>
> PS: Sure, the rule (a+b)**c->a**c+b**c after the expression works  
> fine, but
> its a rule, not an attribute to **, nor to +.
>
> Discussion point: Is there a any reason, why the non-commutative but
> associative opertor ** should not be distributive with respect to a  
> linear
> operator + in general? To my opinion this would be more  
> straightforward, when
> calling the operator a multiplicative one. What do you think?
>
> Thank you
> Christoph
>

What's wrong with just using:


Distribute[(a + b) ** c]

a**c+b**c

?

Andrzej Kozlowski
Tokyo, Japan


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