- GiNaC-list - ginac.de

series of x^n around x=0
by Feng Feng 19 Dec '19

19 Dec '19

Hi all, I got a question while using series on x^n with n a non-integer. here is an example: ------ symbol x("x"); ex expr = pow(x, ex(3)/2); // 3/2 may be a general non-integer cout << expr.series(x,2) << endl; ------ The output is: Order(x^2) so is there a way to handle this? Best regards! Feng

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Undefine the predefined numeric consant 'I'?
by Warren Weckesser 03 Nov '19

03 Nov '19

Is there an easy way to undefine the predefined numeric value 'I'? If I define a symbol 'I', use it in an expression, and then output that expression to cout after modifying stream with csrc, 'I' is converted to 'std::complex<double>(0.0,-1.0)'. I'd like the output to be just 'I'. Warren

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Question: "expand" power in ginac
by Clobert von Roum 16 Oct '19

16 Oct '19

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Release 1.7.8
by Richard B. Kreckel 07 Oct '19

07 Oct '19

Hi, GiNaC 1.7.8 has just been released. The changes are: * Fix pseries::evalf(), broken since 1.7.0. * Fix a corner-case bug in H_evalf(). Happy hacking! -richy. -- Richard B. Kreckel <https://in.terlu.de/~kreckel/>

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Release 1.7.7
by Richard B. Kreckel 22 Sep '19

22 Sep '19

Hi, GiNaC 1.7.7 has just been released. It fixes some bugs (see NEWS) and depends on Python3 for build (this may be important for distros). Happy hacking! -richy. -- Richard B. Kreckel <https://in.terlu.de/~kreckel/>

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trigonometric identity s2+c2=1
by Dario Pellegrini 19 Jul '19

19 Jul '19

I noticed that GiNaC does not apply the simplification: cos(x)^2+sin(x)^2 = 1 for any x in R Is there any way for me to force this substitution in my expressions? That would greatly simplify them...

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fsolve system of equation
by Dario Pellegrini 19 Jul '19

19 Jul '19

Hi all. I have a bidimensional system of two nonlinear equations (containing some trigonometric functions) which I would like to solve numerically. I spent few hours searching for an example but I could not find any. Is it possible to achieve this within the GiNaC framework?

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Re: [GiNaC-list] question about lorentz_g contract with sy_anti tensor
by Feng Feng 26 May '19

26 May '19

Thanks very much for your so quick reply. Yes, my mistake, I actually mean A^{abc}_{c} = A^{abcd} * g_{dc} So it goes back to my original post, it seems GiNaC will not produce a 0 result. Thanks again! Best Regards! Feng

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Re: [GiNaC-list] question about lorentz_g contract with sy_anti tensor
by Feng Feng 26 May '19

26 May '19

Tanks a lot! Yes and Sorry, I forgot to call simplified_indexed. Still, I get some confused with the index variance. and excuse me to let me explain my options in some details. I understand g_c^d = g_{ce} g^{ed}, and let’s come back to the ret expresion: "auto ret = indexed(A, sy_anti(0,1,2,3), ia,ib,ic,id) *lorentz_g(ic, id.toggle_variance());” In my understanding, it corresponds to A^{abcd} * g^{c}_{d}, is that right? if so, then A^{abcd} * g^{c}_{d} = A^{abcc}, so according to sy_anti, it is 0, directly from GiNaC. So if I want to contract two index in A, I mean, we need this one: A^{abc}_{c} = A^{abcd} * g^{dc} ? Thanks very much! Best Regards! Feng

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Re: [GiNaC-list] question about lorentz_g contract with sy_anti tensor
by Feng Feng 25 May '19

25 May '19

Thanks very for the reply. and I have tried the suggestion, i.e., using the following expression: auto ret = indexed(A, sy_anti(0,1,2,3), ia,ib,ic,id) * lorentz_g(ic, id.toggle_variance()); but I got something like: -delta.d~c*A~d~a~b~c, still a non-zero result. BTW, if c’s variance is not toggled in lorentz_g, then these two dummy index c’s variance is not matched, and is that allowed? Thanks again!

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