#3416: Weierstrass form for cubics
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   Reporter:  moretti                   |          Owner:  was                  
                                     
       Type:  enhancement               |         Status:  needs_work           
                                     
   Priority:  major                     |      Milestone:  sage-4.7.1           
                                     
  Component:  elliptic curves           |       Keywords:  nagell, weierstrass, 
cubic, elliptic curves, editor_wstein
Work_issues:                            |       Upstream:  N/A                  
                                     
   Reviewer:  Marco Streng, Nils Bruin  |         Author:  Niels Duif           
                                     
     Merged:                            |   Dependencies:                       
                                     
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Changes (by mstreng):

  * reviewer:  Marco Streng => Marco Streng, Nils Bruin


Comment:

 Replying to [comment:31 nbruin]:
 > If you are implementing your algorithm "bare bones" (internally, you
 just work with polynomials and you don't use any of the scheme machinery
 and your input consists of a homogeneous poly rather than a plane curve)
 there could be some value of also making your output available "bare
 bones", i.e., just return the list [a1,a2,a3,a4,a6] and a list of
 polynomials describing the map.
 >
 > There is a cost to using schemes, ambient spaces etc., so there may be a
 benefit in having the raw functionality available in a form that avoids
 it. Once you have a routine that does the heavy lifting, it's
 straightforward to write a wrapper that provides an interface in scheme
 language.

 I like this idea. So Niels's code could simply output three lists: the
 [a1,a2,a3,a4,a6] and 2 lists of 3 polynomials each. Outputting instead of
 printing should be an easy enough change.

 And then a new member function of {{{ProjectiveCurve_generic}}} could call
 it (or an analogous "{{{y^2}}}=quartic" function) and convert the output
 to an {{{EllipticCurve...}}} and two {{{SchemeMorphism...}}} objects.

-- 
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/3416#comment:32>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica, 
and MATLAB

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