December 2014 - GiNaC-devel

04 Jun '15

Hi, is there any reason not to define the derivative of the built-in abs() function as either abs(x)/x or csgn(x) ? Currently it has not derivative defined at all. Regards, Jan

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Implicit derivation of functions (re-submission)
by Vladimir V. Kisil 02 Feb '15

02 Feb '15

Dear All, I am resending the patch for implicit derivation of functions. Quote from the previous submission: http://www.ginac.de/pipermail/ginac-devel/2013-November/002053.html " 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) " This issue independently appeared in this discussion: http://www.ginac.de/pipermail/ginac-devel/2014-April/002106.html If it is not included in the core code, then a user need to redefine the entire GiNaC function class to have this feature. Best wishes, Vladimir -- Vladimir V. Kisil email: kisilv(a)maths.leeds.ac.uk -- www: http://maths.leeds.ac.uk/~kisilv/

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[SCM] GiNaC -- a C++ library for symbolic computations branch, master, updated. release_1-4-0-438-gf72e191
by git＠ginac.de 31 Dec '14

31 Dec '14

This is an automated email from the git hooks/post-receive script. It was generated because a ref change was pushed to the repository containing the project "GiNaC -- a C++ library for symbolic computations". The branch, master has been updated via f72e1912c287b73a91fda054c6ca68440fb8d0ca (commit) from cfdc2c31088bb196426dd071de5181248df2e160 (commit) Those revisions listed above that are new to this repository have not appeared on any other notification email; so we list those revisions in full, below. - Log ----------------------------------------------------------------- commit f72e1912c287b73a91fda054c6ca68440fb8d0ca Author: Vladimir V. Kisil <kisilv(a)maths.leeds.ac.uk> Date: Wed Dec 31 18:07:26 2014 +0000 Evaluate abs(z)^(2n) -> z^n * conjugate(z)^n. ----------------------------------------------------------------------- Summary of changes: ginac/inifcns.cpp | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) hooks/post-receive -- GiNaC -- a C++ library for symbolic computations

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