
From:  Ralf Hemmecke 
Subject:  [Axiomdeveloper] Commutative symbols was: Re: Limits in Axiom 
Date:  Mon, 26 Mar 2007 12:51:01 +0200 
Useragent:  Thunderbird 2.0b2 (X11/20070116) 
However, I must say that your expression approach is limited in the sense that it can only deal with commuting objects. Simplifying b*a+a*b to 2*a*b is not correct if b is the differentiation operator D on x and a=X is the "multiplication by x"operator. Then you would have D*X=X*D+1.Of course. Try in SymPy: In [2]: x*y+y*x Out[2]: 2*y*x In [10]: a = Symbol("a", is_commutative=False) In [11]: b = Symbol("b", is_commutative=False)
Hmmm, I would have thought that commutativity is a property of the multiplication of the domain you are working in and not a property of a symbol.
Ralf
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