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Re: define a new object or use the existing?
*To*: mathgroup at smc.vnet.net
*Subject*: [mg24364] Re: [mg24360] define a new object or use the existing?
*From*: Ken Levasseur <Kenneth_Levasseur at uml.edu>
*Date*: Wed, 12 Jul 2000 23:13:07 -0400 (EDT)
*Organization*: UMass Lowell
*References*: <200007090853.EAA15447@smc.vnet.net>
*Sender*: owner-wri-mathgroup at wolfram.com
Maris:
I take it that you intend to represent your twisted polynomials as sums
of twisted terms. You might consider an alternate form - something like
TwistedPolynomial[p,opts] where p is a list of pi's and opts includes
options such as Indeterminate->delta. This is essentially how Al
Hibbard and I implemented polynomials over an arbitrary ring in the
AbstractAlgebra packages that we wrote. I found this representation
quite easy to work with. Of course these objects can be formatted as
you like.
The packages are free to download, examine and use at
http://www.central.edu/eaam.html. A guide with labs is available at http://www.telospub.com/catalog/MATHEMATICA/AAwM.html
Ken Levasseur
Maris Tõnso wrote:
>
> Hi!
>
> I am trying to write a program which could handle noncommutative twisted
> polynomials. A noncommutative polynomial has a form
>
> p(delta) = pn**delta^n + ... + p2**delta^2 + p1**delta + p0,
>
> where ** denotes noncommutative multiplication. I can not decide, which
> is better way to represent an object pi**delta^i : to define additional
> rules for function NonCommutativeMulitply or to build a special new
> object on
> this purpose, for example Twisted[pi,i].
>
> You will probably say that it depends on concrete circumstances or
> there is no difference in principle; but I still hope you can give some
> comments
> on this problem.
>
> And the other problem: If I choose to build a new object when I would
> like object
> Twisted[p, n]
> in StandardForm to be printed as
> p delta^n.
> One way to get it is to use Format and Postfix:
> Format[Twisted[p_,n_]] := Postfix[{p}, delta^n ]
> But this solution does not satisfy me.
>
> I would like to know if there exists a elegant way to define the
> formatting for the object Twisted so that
> Twisted[p+q, n] would printed as (p+q) delta^n (not p+q delta^n) and
> Twisted[1, n] would printed as delta^n (not 1 delta^n).
>
> Thanks for any advices.
>
> Maris Tonso
> Tallinn, Estonia
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