May 2007 - GiNaC-devel

Re: Clifford base names WAS: Re: [GiNaC-list] How can I get a GiNaC::ex's name
by Vladimir Kisil 25 May '07

25 May '07

Dear Javier, >>>>> "JRG" == Javier Ros Ganuza <jros(a)unavarra.es> writes: JRG> It woul be interesting to have this posibility, tough elements JRG> of diferent basis are right now plotted in the same way. Indeed it may be worth to see a difference in the output for Clifford units with different representation labels. I include a patch which give this in the way which is shown by such an example: #include <ginac/ginac.h> using namespace std; using namespace GiNaC; int main() { try { varidx mu(symbol("nu", "\\nu"), 3); ex basis1 = clifford_unit(mu, diag_matrix(lst(1, 1, 1)),0), basis2 = clifford_unit(mu, diag_matrix(lst(1, 1, 1)),1); ex e00 = basis1.subs(mu == 0), e10 = basis2.subs(mu == 0); cout << e00 << endl; // <-- e~0 cout << e10 << endl; // <-- e[1]~0 } catch (exception &p) { cerr << "Got problem: " << p.what() << endl; } } Best wishes, Vladimir -- Vladimir V. Kisil email: kisilv(a)maths.leeds.ac.uk -- www: http://maths.leeds.ac.uk/~kisilv/

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Symbolic Integration
by Remco Bloemen 16 May '07

16 May '07

Dear developers, I have been using the Ginac library for some of my hobby programs now and I believe a generic C++ CAS would be very valuable. I have grown interest in symbolic integration and tried implementing polynomial factorization, it seems quite hard to do efficiently, but doable. I have even bought the book mentioned in the todo list (the second edition). Altough I have just began to read it the book mentions that some recent algorithms for trancedental integration do not require polynomial factorization. So I would like to try and implement one of these algo's. My question is, what are your thoughts on how to implement integration in a nice fashion? I tought about implementing some kind of antiderivative operator wich can be used in expressions and gives the indefinite integral. The reason I preffer operators to member function is that it allows unsolvable integrals to remain in the equation and still be numerically evaluable. In this fashion I would like to create a differential operator so ODE's and PDE's can be expressed in Ginac and numerically solved. The hobby program I am trying to make should become a generic numerical integrator for arbitrary PDE's by dynamicaly generating code. I already have a class that converts an expression to its Chebyshev-Pade approximation, compiles it to double arithmetic and dynamicly links it in. So gentleman, what are your thoughts? Sincerely, R. Bloemen

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Problem with power series
by Stefan Weinzierl 16 May '07

16 May '07

Gentlemen, I came across a small problem, when calculating series expansions. The following code hangs, when attempting to compute the expansion: #include <iostream> #include <ginac/ginac.h> using namespace std; using namespace GiNaC; int main() { symbol x("x"); ex e1 = pow(2,x)*( 1/x*(-(1+x)/(1-x)) + (1+x)/x/(1-x)); cout << e1 << endl; cout << e1.expand() << endl; cout << e1.series(x,1) << endl; } I tried it with GiNaC 1.3.7 as well as 1.3.1 and 1.3.0. e1 is actually a complicated zero, and the correct answer should we O(x). Best wishes, Stefan

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