March 2019 - GiNaC-devel

evalf() on cube roots
by Jan Rheinländer 21 Sep '19

21 Sep '19

Picking up this old thread... I would like to submit a patch that allows choosing the convention for negative cube roots between the solution on the principal branch and the real-valued solution. That is, in the cln library, file complex/transcendental/cl_C_expt_C.cc I would like to handle the following case separately: y rational and y ratio m/n x rational and x < 0 n odd What about introducing a flag called (e.g.) cln::cl_odd_roots_of_rationals_real (similar to cln::cl_inhibit_floating_point_underflow)? If the flag is false (default), the above case evaluates to exp(log(x) * y) as before If the flag is true, it evaluates to (-1)^m * (-x)^(m/n) Would such a patch be acceptable? Greetings, Jan Rheinländer Am 02.08.2015 um 21:55 schrieb Richard B. Kreckel: > On 08/02/2015 08:59 PM, Jan Rheinländer wrote: >>> There isn't. GiNaC, like almost all other systems, returns the solution >>> on the principal branch, compatible with exp(log(-1)/3). >> I suppose there is some excellent mathematical reason for this... > Actually, there isn't. Branch cuts are a matter of convention. > Nothing more but also nothing less. > >> but for >> me it means that I can't use GiNaC to verify Cardano's formula for a >> cubic function: >> >>> x = (-1 - sqrt(2))^(1/3) + (-1 + sqrt(2))^(1/3); >> (-1-sqrt(2))^(1/3)+(-1+sqrt(2))^(1/3) >> >>> evalf(x^3 + 3 * x + 2); >> 3.3544445609126528848+8.9073474964875349776*I >> >> Surely there must be a way to verify such a formula in GiNaC??? > It should be straightforward to replace such rational expressions by the > form you want them to be in before calling evalf(), using techniques > such as these: <http://www.ginac.de/FAQ.html#advanced> > > Cheers > -richy.

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[SCM] GiNaC -- a C++ library for symbolic computations branch, master, updated. release_1-4-0-624-g3d962a6e
by Richard B. Kreckel 22 Mar '19

22 Mar '19

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 3d962a6ef2acd92207cdfc164a33d13c5c827dc9 (commit) from f243b5cccfd8ff57115f0b0d5ade20bcca23ae1f (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 3d962a6ef2acd92207cdfc164a33d13c5c827dc9 Author: Stefan Weinzierl <weinzierl(a)uni-mainz.de> Date: Fri Mar 22 10:01:30 2019 +0100 Fix bug in inifcns_nstdsums.cpp... ...related to trailing zeros in combination with user-specified signs for small imaginary parts. When the trailing zeros are shuffled away, the information on the signs of the small imaginary parts has to be kept. This bug was reported by Dmitry Chicherin. ----------------------------------------------------------------------- Summary of changes: ginac/inifcns_nstdsums.cpp | 29 +++++++++++++++++++++++++++-- 1 file changed, 27 insertions(+), 2 deletions(-) hooks/post-receive -- GiNaC -- a C++ library for symbolic computations

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bug fix for inifcns_nstdsums.cpp
by Stefan Weinzierl 20 Mar '19

20 Mar '19

Dear all, attached is a patch, which fixes a bug in inifcns_nstdsums.cpp, related to trailing zeros in combination with user-specified signs for small imaginary parts. When the trailing zeros are shuffled away, the information on the signs of the small imaginary parts has to be kept. This bug was reported by Dmitry Chicherin. Best wishes, Stefan

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[SCM] GiNaC -- a C++ library for symbolic computations branch, master, updated. release_1-4-0-623-gf243b5cc
by Richard B. Kreckel 09 Mar '19

09 Mar '19

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 f243b5cccfd8ff57115f0b0d5ade20bcca23ae1f (commit) via ec64e556734484ca3c518e6de95b26be61bedee7 (commit) via 9431fba22d0523bba51a0fc3e488627594af0884 (commit) from 8643e3cba4f229faba5d1aeb9a7b31ba609f81fb (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 f243b5cccfd8ff57115f0b0d5ade20bcca23ae1f Author: Richard Kreckel <kreckel(a)ginac.de> Date: Sat Mar 9 18:40:32 2019 +0100 Refactor matrix::determinant_minor() a bit. Remove special cases for small matrices and for for last column minor computation. Add early return for the case that all minors relevant for one column turn out to be zero. Improve some comments. commit ec64e556734484ca3c518e6de95b26be61bedee7 Author: Richard Kreckel <kreckel(a)ginac.de> Date: Fri Mar 8 22:33:44 2019 +0100 [DOC] Fix examples using deprecated lst initializers. commit 9431fba22d0523bba51a0fc3e488627594af0884 Author: Richard Kreckel <kreckel(a)ginac.de> Date: Thu Mar 7 20:57:50 2019 +0100 Refactor module static helper functions to helper class. Functions symbolset and insert_symbols in inifcns.cpp are better written as a class, to improve readability. ----------------------------------------------------------------------- Summary of changes: doc/tutorial/ginac.texi | 19 ++++------- ginac/inifcns.cpp | 48 ++++++++++++++------------ ginac/matrix.cpp | 89 ++++++++++++++++++++++--------------------------- 3 files changed, 74 insertions(+), 82 deletions(-) hooks/post-receive -- GiNaC -- a C++ library for symbolic computations

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