October 2018 - 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_1-4-0-615-g96be7a17
by Richard B. Kreckel 12 Oct '18

12 Oct '18

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 96be7a17790700998e2d071e00ad5c1ffb4a2d3e (commit) from a039abd06ed205ed9868ff1ceb1378082f8cb1ab (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 96be7a17790700998e2d071e00ad5c1ffb4a2d3e Author: Vitaly Magerya <vmagerya(a)gmail.com> Date: Fri Oct 12 20:45:27 2018 +0200 Handle un-normal zeros properly in the division-free elimination. Call .normal() instead of just .expand(), such that matrix::pivot() finds the pivot. Note that this problem also affects matrix::solve() with 'algo' set to solve_algo::automatic. Of course, using .normal() makes division_free_elimination only truly "division-free" if the input matrix didn't have fractions. In other cases, GCDs will be computed. ----------------------------------------------------------------------- Summary of changes: check/exam_matrices.cpp | 26 ++++++++++++++++++++++++++ ginac/matrix.cpp | 2 +- 2 files changed, 27 insertions(+), 1 deletion(-) hooks/post-receive -- GiNaC -- a C++ library for symbolic computations

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[SCM] GiNaC -- a C++ library for symbolic computations branch, master, updated. release_1-4-0-614-ga039abd0
by Richard B. Kreckel 04 Oct '18

04 Oct '18

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 a039abd06ed205ed9868ff1ceb1378082f8cb1ab (commit) via 1109fafaa3f5da6d1483744c4bdee6f01a37c5c5 (commit) from 45ca93fc48c14f733de73ffbbfef0834be731b08 (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 a039abd06ed205ed9868ff1ceb1378082f8cb1ab Author: Richard Kreckel <kreckel(a)ginac.de> Date: Thu Oct 4 21:32:21 2018 +0200 Update m4/ax_cxx_compile_stdcxx.m4 to current upstream version. commit 1109fafaa3f5da6d1483744c4bdee6f01a37c5c5 Author: Richard Kreckel <kreckel(a)ginac.de> Date: Thu Oct 4 21:28:42 2018 +0200 [DOC] Explaining in tutorial sign ambiguity for numer() and denom(). Based on a patch provided by Vladimir V. Kisil <kisilv(a)maths.leeds.ac.uk>. ----------------------------------------------------------------------- Summary of changes: doc/tutorial/ginac.texi | 7 +++++-- m4/ax_cxx_compile_stdcxx.m4 | 42 ++++-------------------------------------- 2 files changed, 9 insertions(+), 40 deletions(-) hooks/post-receive -- GiNaC -- a C++ library for symbolic computations

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