[GiNaC-list] Parse error involving factorial symbol

Vladimir V. Kisil V.Kisil at leeds.ac.uk
Sat May 15 22:01:49 CEST 2021

	Dear Roberto,

	Yes, normalisation methods in GiNaC undergone some modification
  over that period as well. Thus particular form of the expression can
  be different now.

  Best wishes,
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
>>>>> On Fri, 14 May 2021 22:36:13 +0200, Roberto Bagnara <bagnara at cs.unipr.it> said:

    RB> On 5/14/21 3:33 PM, Vladimir V. Kisil wrote:
    >>>>>>> On Fri, 14 May 2021 15:08:09 +0200, Roberto Bagnara
    >>>>>>> <bagnara at cs.unipr.it> said:
    RB> On 5/14/21 9:52 AM, Vladimir V. Kisil wrote:
    >> >> Dear Roberto!  It seems that Ginsh and parser in GiNaC are >>
    >> implemented differently. Ginsh understands postfix factorial >>
    >> notation like "3!"  but GiNaC parser is not. GiNaC parser is >>
    >> still happy with "factorial(3)".  Best wishes, Vladimir
    >> >>
    RB> Thanks Vladimir!  But please help me understand: I did not
    RB> change anything in the part of the code invoking the GiNaC
    RB> parser, and I did not change the tests.  So the situation you
    RB> are describing, i.e., GiNaC parser not understanding postfix
    RB> factorial notation, is something that changed from, say, 10
    RB> years ago.  In other words, do you agree that, say, 10 years
    RB> ago, the GiNaC parser was accepting that notation?
    >> It seems that before 2008-08-21 GiNaC and Ginsh had used the same
    >> parser, which Ginsh is using till now. After a patch they
    >> diverged in this respect. So it is quite well possible that your
    >> code was running with the old version of GiNaC but cannot do this
    >> now without some alteration.

    RB> Dear Vladimir,

    RB> This explains everything.  Now I am investigating failures in
    RB> the regression test-suite.  One of the most promising examples
    RB> for my diagnosis efforts is this:

    RB> simplification for output of
    RB> -1+1/12*sqrt(sqrt(3)*sqrt(12))*sqrt(12)+1/12*sqrt(-sqrt(3)*sqrt(12))*sqrt(12)
    RB> was expected to be -1+(1/2+1/2*I)*sqrt(2) but resulted in
    RB> -1+(1/2+1/2*I)*4^(1/4)

    RB> From what you write I gather that back in 2008, or even before,
    RB> we obtained sqrt(2) where we now obtain 4^(1/4).

    RB> Thanks,

    RB>    Roberto

    RB> -- Prof. Roberto Bagnara Applied Formal Methods Laboratory
    RB> Department of Mathematical, Physical and Computer Sciences
    RB> University of Parma, Italy http://www.cs.unipr.it/~bagnara/
    RB> mailto:bagnara at cs.unipr.it

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