[GiNaC-devel] Improving normalisation with negative exponents

[Vladimir V. Kisil]

	Dear All,

	With version 1.8.0 of GiNaC the following code

 realsymbol x("x");
 ex e = (exp(2*t)-exp(-2*t))/(exp(t)-exp(-t));
 cout << e.normal() << endl;

   will through an exception

terminate called after throwing an instance of 'std::logic_error'
  what():  heur_gcd: not an integer polynomial [1]

  The reason is that internally e will be converted to something like

  (symbol457^2-symbol457^(-2))/(symbol457 - 1/symbol457)

  with non-polynomial numerator and denominator.

  I am attaching a patch which will fix this issue. Some additional
  tests are included as well.

  Best wishes,
  Vladimir
-- 
Vladimir V. Kisil                 http://www.maths.leeds.ac.uk/~kisilv/
  Book:      Geometry of Mobius Maps       https://doi.org/10.1142/p835
  Soft:      Geometry of cycles         http://moebinv.sourceforge.net/
  Jupyter notebooks:       https://github.com/vvkisil/MoebInv-notebooks


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