#21088: Base Class for Skew Polynomials over Finite Fields
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       Reporter:  arpitdm            |        Owner:
           Type:  enhancement        |       Status:  new
       Priority:  major              |    Milestone:  sage-7.3
      Component:  coding theory      |   Resolution:
       Keywords:                     |    Merged in:
        Authors:  Xavier Caruso,     |    Reviewers:
  Arpit Merchant                     |
Report Upstream:  N/A                |  Work issues:
         Branch:                     |       Commit:
  u/arpitdm/finite_fields_skew_polynomial|  
a6e93e12c1fefffde3615c8eab75a45b3c277ab2
   Dependencies:  #13215             |     Stopgaps:
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Comment (by jsrn):

 Replying to [comment:10 arpitdm]:
 > Replying to [comment:4 jsrn]:
 > Based on the discussions before, the plan was to add these in the finite
 fields ticket.

 Yes, at that point I hadn't realised that all the functions apply to
 general skew polynomial rings.

 > That meant these had to either go in the general or finite field ring
 classes. I looked up some papers and found that the theory for polynomial
 interpolation of skew polynomial rings exists, although I didn't really
 try and study any of that. I just went kinda assumed that the algorithms
 by Wachter-Zeh would be valid and placed it there.

 I don't know what to reply to that. If you don't *know*, then 1) try to
 figure it out, using math; and if you fail at that 2) ask (and we will try
 to do step 1 ourselves). By now you should be well-enough versed in the
 basics of skew polynomials that you at least shouldn't try to put q-powers
 everywhere. I would have expected you just to put the functions it in the
 finite field-class since that is the only case that you studied. If you
 thought it might apply generally, you should prove it and/or discuss with
 us.

 Your "mistake" of course lead me to reflect upon it, which turned out for
 the better, but still.

 > Just to confirm again, should I create a new ticket and place them
 there?

 Yes please, as they do not pertain specifically to finite fields.

 > >       - Given a singleton point a, return x - sigma(a)/a.   (use pen-
 and-paper to see that I am right)
 > If the singleton point is 0, I simply return x and otherwise x -
 sigma(a)/a as you pointed out, right?

 0 is not a valid input. 0 does not span a vector space (well, it spans a
 vector space of dimension 0), and *any* skew polynomial evaluates to 0 on
 0.

 > > - `x = self([0,1])` should be `x = self._parent.gen()`.
 > um.. you mean self.gen(), right? Because self._parent.gen() would give
 an error.

 Yes I meant `self.gen()`.

 > Done. And I'll report back with some timing results once I test that
 these are working properly.

 OK.

--
Ticket URL: <https://trac.sagemath.org/ticket/21088#comment:12>
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