January 2013 - GiNaC-list

Creating a number of FUNCTION_1P
by Dale Lukas Peterson 20 Feb '13

20 Feb '13

I am trying to declare N GiNaC 1 parameter functions (DECLARE_FUNCTION_1P), each of which represents a different function of the same single parameter (in my case, this parameter represents time). My primary motivation for doing this is to be able to easily create a bunch of symbol-like objects that all depend on time so that I can trust that the chain rule will work properly when differentiating with respect to this single parameter. I think this has come up before, but I haven't seen a way to declare a vector or list of these functions without N explicit statements to DECLARE_FUNCTION_1P. Is there a simple way to do this in GiNaC? Thanks, Luke

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Re: [GiNaC-list] set_TeX_name() ?
by Dale Lukas Peterson 23 Jan '13

23 Jan '13

> Just as a suggestion: instead of an introduction of a separate > method set_TeX_name(), may be simpler to modify set_name() to have an > optional second argument for the Tex name (similar to the symbol() > method). Here are the three options I can see. First, a default parameter as I think you are suggesting: void set_name(const std::string & n, const std::string & texname = "") { name = n; TeX_name = texname; } Second, overloading set_name: void set_name(const std::string & n) { name = n; } void set_name(const std::string & n, const std::string & texname) { name = n; TeX_name = texname; } Third, the option I originally proposed: void set_TeX_name(const std::string & n) { TeX_name = n; } I prefer my original proposal since it seems the most orthogonal to me. But any of them is really fine with me so that there is a way to change the TeX_name after you've created an instance of symbol. If there is interest in keeping fewer methods, then I guess one of the first two options would be preferable. Thanks, Dale

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Automatic simplification of C# expressions
by Eduardo Cavazos 20 Jan '13

20 Jan '13

Hello, I've started building a small library which implements automatic simplification of C# expressions: https://github.com/dharmatech/Symbolism I guess this is mostly off-topic, so sorry about that. I wanted to mention the library here because GiNaC has been hugely influential (as has SymbolicC++). It's a very limited library, but I think it might be useful for someone wanting to experiment with building GiNaC type functionality in C# without starting from scratch. Ed

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How can I build an expression one character at a time?
by Roger Gordon 08 Jan '13

08 Jan '13

Hi guys, I recently started using ginac, and one thing I couldnt figure out from the tutorial is how can I make an expression one piece at a time. So if I wanted to build an expresison out of a list like x,=,5,*,4 I imagine doing something like ex expr; expr.append(x); expr.append(==); expr.append(5); expr.append(4); I understand the numbers are numerics, and x would be a symbol, but I dont know what the operators would be ( * / + - ). Does anyone how I can do this? Does this even make any sense to you? Thanks for any replies! R. Gordon

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Simple question about how to solve for a simple non-linear system of equations.
by Zach 06 Jan '13

06 Jan '13

Hi guys I know this is a really basic question but after looking at the tutorial and reference I couldn't quite figure out how to solve a nonlinear system of equations. (If this is even possible, I dont know). I have this: lst eqns, vars; > > eqns = D==pow(T,2); > > vars =T; > > ex L = lsolve(eqns,vars); > But lsolve (I guess the l for linear makes it obvious) cannot solve this nonlinear function. Is there another way I can accomplish this? Then I could do something like: ex ans = L.subs(lst(D==3)); like I would for a linear? Is this even possible? Thanks for any answer! Ginac is a great tool for me so far!

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