- GiNaC-list - ginac.de

user defined functions and constants
by Gunnar Birke 26 Sep '13

26 Sep '13

Hello guys, I'm working on a CAS for school mathematics in C++ and want to use GiNaC as a backend. In a CAS, the user has the option to define constants and functions, for example def a = 5 def f(x) = 2 * x + 3 def g(x, y) = x + 2y and then use these definitions like this f(3) + a * 4 - g(4, 5) Implement this for constants is pretty straight forward in GiNaC with the subs() method and an exmap which contains all defined constants. For the example above, it would be enough to insert a symbol with the value a together with the expression 5 into the map, then call subs() with it. Enable the same support for functions however seems very difficult, as functions can only defined at compile time with a macro. And using subs() seems a bit silly with functions: GiNaC::ex ex(f(2)); ex.subs(f(2) == f(2)); //what? This problem seems pretty common to me and I really wondered why GiNaC has no options to archive this. Did I miss something?

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Multiplication of Boolean variables
by tklam 02 Sep '13

02 Sep '13

Hi, I am implementing an arithmetic system for only Boolean variables based on GiNaC. May I know how I can modify the behaviour of symbolic multiplication such that: x*x == x (instead of x*x==x^2), and the multiplication of numeric remains unchanged (eg 3*4 == 12) ? Using subs(x^2 == x) works but I found it is slow if my expressions are huge and there are many symbols. Thank you very much. Best regards, argama

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GiNaC Match Documentation
by Mark Round 15 Aug '13

15 Aug '13

I have been encountering problems with the GiNaC function match. Basically I can not understand the documentation. I wanted to detail my story in the hope that perhaps my problems are solved and in the future someone else can avoid my pitfalls. The documentation informs me that I need an associative array. I can not find how to construct such an array elsewhere in the documentation so I assume that I am supposed to use exhashmap. That was a point of confusion for me. Then I designed the following code snipet, symbol x("x"), y("y"); ex tmp=x+y; exhashmap <ex> array; tmp.match(wild(1)+y); which apparently works fine. Now I wish to fill 'array' with the replacement table. So I modified to, tmp.match(wild(1)+y,array); which returned the following compiler messages, momentum_integration.cpp: In function ‘GiNaC::ex bring_to_parameterisable_form(GiNaC::ex)’: momentum_integration.cpp:13:33: error: no matching function for call to ‘GiNaC::ex::match(const GiNaC::ex, GiNaC::exhashmap<GiNaC::ex>&)’ momentum_integration.cpp:13:33: note: candidates are: In file included from /usr/include/ginac/ginac.h:30:0, from momentum_integration.h:14, from momentum_integration.cpp:1: /usr/include/ginac/ex.h:150:7: note: bool GiNaC::ex::match(const GiNaC::ex&) const /usr/include/ginac/ex.h:150:7: note: candidate expects 1 argument, 2 provided /usr/include/ginac/ex.h:151:7: note: bool GiNaC::ex::match(const GiNaC::ex&, GiNaC::exmap&) const /usr/include/ginac/ex.h:151:7: note: no known conversion for argument 2 from ‘GiNaC::exhashmap<GiNaC::ex>’ to ‘GiNaC::exmap& {aka std::map<GiNaC::ex, GiNaC::ex, GiNaC::ex_is_less>&}’ make: *** [momentum_integration.o] Error 1 I attempted to use the command exmap but I can not find anything on that in the documentation. I tried several permutations around, exmap <ex,ex> array; which made the compiler return, momentum_integration.cpp: In function ‘GiNaC::ex bring_to_parameterisable_form(GiNaC::ex)’: momentum_integration.cpp:11:8: error: ‘GiNaC::exmap {aka std::map<GiNaC::ex, GiNaC::ex, GiNaC::ex_is_less>}’ is not a template make: *** [momentum_integration.o] Error 1 At which point it is unclear to me what else I should try. The code was ran on a 64-bit Linux Mint-Debian distribution with ginac-1.6.2.

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ginac 1.6.2-2 on mingw-32.
by testhandle 07 Aug '13

07 Aug '13

(most of this text was written using google translate. english is not good at me. so there's a possibility that the meaning is not transmitted.) there may be unnecessary operation and defects. however, it is forced by this operation, but it have confirmed the operation of the tutorial examples. * step 0, dependencies. gmp 5.0.1 cln (gmp) 1.3.3 gcc 4.7.2 ld 2.23.1 m4 1.4.16 autoconf 2.68 autoreconf 2.68 automake 1.11 libtool 2.4 python 2.7.3 bison 2.4.2 flex 2.5.35 * step 1. $ git clone git://www.ginac.de/ginac.git * step 2, modify the 'ginac/config/config.rpath'. line 67: replace mingw* | pw32* | os2*) -> pw32* | os2*) line 57: insert mingw*) wl='Wl,' ;; line 135: replace cygwin* | mingw* | pw32*) -> cygwin* | pw32*) line 185: replace cygwin* | mingw* | pw32*) -> cygwin* | pw32*) line 199: replace linux*) -> linux* | mingw*) * step 3. $ cd ginac $ autoreconf -i * step 4, modify the 'ginac/configure'. line 15539: delete * step 5, modify the 'ginsh/ginsh_lexer.lpp'. line 37: replace #include "ginsh_parser.hpp" -> #include "ginsh_parser.h" * step 6. $ export CLN_LIBS="-L/usr/local/lib -lcln -lgmp" $ export CLN_CFLAGS="-I/usr/local/include" $ ./configure $ make $ make install * test 1. // hello.cpp ---------------- #include <iostream> #include <ginac/ginac.h> using namespace std; using namespace GiNaC; int main() { symbol x("x"), y("y"); ex poly; for (int i=0; i<3; ++i) poly += factorial(i+16)*pow(x,i)*pow(y,2-i); cout << poly << endl; return 0; } $ g++ -c -O3 -I/usr/local/include -L/usr/local/bin hello.cpp $ g++ -o hello hello.o -lginac -lcln -lgmp &> result.txt $ ./hello 355687428096000*x*y+20922789888000*y^2+6402373705728000*x^2 * test 2. // hello2.cpp ---------------- #include <iostream> #include <ginac/ginac.h> using namespace std; using namespace GiNaC; ex HermitePoly(const symbol & x, int n) { ex HKer=exp(-pow(x, 2)); // uses the identity H_n(x) == (-1)^n exp(x^2) (d/dx)^n exp(-x^2) return normal(pow(-1, n) * diff(HKer, x, n) / HKer); } int main() { symbol z("z"); for (int i=0; i<6; ++i) cout << "H_" << i << "(z) == " << HermitePoly(z,i) << endl; return 0; } $ g++ -c -O3 -I/usr/local/include -L/usr/local/bin hello2.cpp $ g++ -o hello2 hello2.o -lginac -lcln -lgmp &> result.txt $ ./hello2 H_0(z) == 1 H_1(z) == 2*z H_2(z) == -2+4*z^2 H_3(z) == -12*z+8*z^3 H_4(z) == 12+16*z^4-48*z^2 H_5(z) == 120*z+32*z^5-160*z^3

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Numeric and Constants
by David Narvaez 13 Jul '13

13 Jul '13

Hi, While implementing a GiNaC based backend for my software I decided to replace doubles by GiNaC::exs. That seemed to work fine until I actually needed the final native value of the expression, so I changed my mind to use GiNaC::numerics instead, which works fine except for constants, since I'm unable to do things like GiNaC::numeric angle = 2 * GiNaC::Pi; is there a quick way to pass from a constant to a numeric? (or alternatively a way to turn expressions into doubles and I should go back to GiNaC::ex). Thanks in advance. David E. Narvaez

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variable isolation
by Andrea Monzali 12 Jun '13

12 Jun '13

Good evening everybody, I'm new to ginac, i read the tutorial but i've a question, if I have an equation expression, something like symbol x("x"), y("y"); ex eq = 2*x + 3*x*y - 5*y == 0 is there a method to isolate a single variable, i.e. cout << isolate(eq, x) << endl; // x == 5*y*(2 + 3*y)^(-1) cout << isolate(eq, y) << endl; // y == 2*x*(5 - 3*x)^(-1) thanks for all replies.. -am

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Fwd: find series roots with Ginac
by Jey Nadarasa 22 Apr '13

22 Apr '13

Hello everyone, I would like to know if it is possible to find series roots with Ginac ? That's all for the moment, Advance thanks for your answer, Best Regards, JN

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[(Possible) Bug Report] g++-4.8 (slightly) breaks GiNaC::symbol
by Song Gao 25 Mar '13

25 Mar '13

Hey, I had a weird problem using GiNaC with g++-4.8. It seems that GiNac::symbol will be deleted twice if it's not dynamically declared. In other words, some resources in it is free'd before the automatic destructor is called when the scope finishes. The minimum code to re-produce the issue is: #include <ginac/ginac.h> int main() { GiNaC::symbol x("x"); return 0; } $ g++-4.8 -g -o main main0.cc -lginac -lcln && ./main main(69018) malloc: *** error for object 0x7fff73275570: pointer being freed was not allocated It seems this issue only exists in g++-4.8. g++-4.7 is fine. I briefly looked at symbol.h but did not manage to locate the problem. I was hoping someone here more familiar with the code base could fix it or provide some direction for me. Thanks. -- Song Gao http://song.gao.io/

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GiNaC Multithreading
by Florian 09 Mar '13

09 Mar '13

Hi, I have read the issue of multithreading from 2010 and I wonder whether there has been attempt to make GiNaC thread-safe. I think that it shouldn't be a big deal to make the shared data like the refcounter atomic (e.g. using std::atomic< T >) or to the synchronize it's manipulation (e.g. using std::mutex). Best regards, Florian -- Florian Corzilius RWTH Aachen University Computer Science Department, Informatik 2 D-52056 Aachen, Germany http://www-i2.informatik.rwth-aachen.de/i2/corzilius/ phone: +49 241 80-21244

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cmake msvc build
by Philipp Kraus 25 Feb '13

25 Feb '13

Hello, I love GiNaC and I can build it with MSYS very well. My question is for a feature request is: Can a cmake build added, so that I can build GiNaC native under MSVC? I think this can be a nice solution. Thanks Phil

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