[GiNaC-devel] Releasing?

[Vladimir V. Kisil]

	Dear All,
>>>>> On Sun, 03 Nov 2013 23:36:36 +0100, "Richard B. Kreckel" <kreckel at ginac.de> said:
    RK> And, in particular, @Alex and @Vladimir: do you have things in the pipeline?

    I wish to propose another GiNaC extension. Consider function
  abs(). Since it can be presented as abs(z)=sqrt(z*z.conjugate()), the
  derivative of abs(f) may be calculated as

  (abs(f))'=(f'*f.conjugate()+f*f'.conjugate())/2/abs(f)

  However, this formula cannot be packed into the present GiNaC code,
  since it only knows about the chain rule. Thus, the patch adds a
  possibility to define derivatives of functions in some general
  expression. In particular, the above derivative of abs() is
  defined. Example: 

  cout << abs(log(z)).diff(z) << endl;
  // (before) -> D[0](abs)(log(z))*z^(-1)
  // (now) -> 1/2*(z^(-1)*conjugate(log(z))+log(z)*conjugate(z)^(-1))*abs(log(z))^(-1)
  
  Best wishes,
  Vladimir
-- 
Vladimir V. Kisil     email: kisilv at maths.leeds.ac.uk
                        www: http://www.maths.leeds.ac.uk/~kisilv/
Book: Geometry of Mobius Transformations
http://www.worldscientific.com/worldscibooks/10.1142/p835

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