- GiNaC-list - ginac.de

Any way to get the leading order of a series expansion?
by Vitaly Magerya 16 May '23

16 May '23

Hi, all. We have some code needs to have the first N orders of a series expansion of an expression; so far we've been actually using sympy for this: there one can use series() [1] directly, as it computes "the first N orders", whereas in GiNaC series() expands "up to N-th order", so if I just need e.g. the leading order, then series() can't help me directly. Any idea of how can one get the leading order, or the first N orders with GiNaC? Would this need a lot of effort to implement? [1] https://docs.sympy.org/latest/modules/series/series.html#sympy.series.serie…

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Polynomial Factoring
by Charles White 05 May '23

05 May '23

Hi GiNaC! I love the library! Keep up the good work! Currently I am trying to find exact eigenvalues. My solution so far is to factor the characteristic equation then I can try to find roots of the factored polynomials. But, I need a list of expressions that store the factored polynomials. For example in the ginsh I have: ``` > rat = pow(x,6)+1; 1+x^6 > factor(rat); (1+x^4-x^2)*(1+x^2) ``` Then I need a list with the expressions (1+x^4-x^2) and (1+x^2); from there I can calculate the roots exactly. Is this possible? Is there a better way to find exact eigenvalues? Thanks! Charles

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How to express and simplify symbolic expressions in Ginac?
by Anubhavnidhi Abhashkumar . 20 Apr '23

20 Apr '23

Hi, I am pretty new to GiNac library in c++ and am struggling with one particular topic. I have been using ginac-1.8.6 I want to represent and simplify symbolic expressions (expressions with union, intersection, and not operator) with GiNac. I have been trying the following example #include <iostream>#include <ginac/ginac.h>using namespace std;using namespace GiNaC; int main(){ symbol x("x"), y("y"), z("z"); ex boolean_expr = (!x || y) && (x || z); cout << "Boolean expression: " << boolean_expr << endl; ex simplified_expr = normal(boolean_expr); cout << "Simplified expression: " << simplified_expr << endl; return 0; } But I keep on getting errors related to ||, !, and && operators. For example, > note: candidate: ‘operator!(bool)’ <built-in> > note: no known conversion for argument 1 from ‘GiNaC::symbol’ to `bool’ > error: no match for ‘operator!’ (operand type is `GiNaC::symbol’) I also tried replacing ||, !, and && to or, not, and, respectively but get similar errors > error: no match for ‘operator!’ (operand type is ‘GiNaC::symbol’) ex boolean_expr = not(x) or y and (x or not(z)); So my question is how can I represent and, or, not. I am using Ginac 1.8.6 from here <https://www.ginac.de/Download.html>. I also checked the manual here <https://www.ginac.de/tutorial.pdf> but did not find an answer. Thanks, Archie http://anubhavnidhi.github.io/

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LaTeX Output
by Charles White 18 Apr '23

18 Apr '23

Hi GiNaC! I love the library! Keep up the good work! Currently though I am having trouble with LaTeX output; I would like to parse an expression, then set the LaTeX name to the symbols that were generated from the reader. I can do that, but the expression doesn't change when I print it. Here is an minimal example: #include <ginac/ginac.h> std::string addTeXbrackets(std::string const& in) { std::string ret = in; std::string::size_type pos = 0; while((pos = ret.find('_', pos)) != std::string::npos) { ret.replace(pos, 1, "_{"); pos += 1; // move past the dot (and the extra '\n') ret.push_back('}'); } return ret; } int main(){ GiNaC::parser reader; GiNaC::ex e = reader("2*x_1+sin(y_2)"); GiNaC::symtab & vars = reader.get_syms(); std::cout << GiNaC::latex; for (std::pair<std::string, GiNaC::ex> var : vars) { // loop through each symbol then texify and use "set_TeX_name()" GiNaC::ex_to<GiNaC::symbol &>(var.second).set_TeX_name(addTeXbrackets(var.first)); std::cout<<var.second<<std::endl; } //<- Not sure how to add latex to the output yet std::cout<<e<<std::endl; } //output is: x_{1} y_{2} 2 x_1+\sin(y_2) Thanks! Charles

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feature request
by Marko Riedel 22 Feb '23

22 Feb '23

Greetings to all. Continuing with my GiNaC project I have noticed that there was some functionality missing that other software offers. In particular, I require **factorization of integers** and a function to compute the **set of divisors** of an integer. I have implemented these using basic math such as might be used in a freshman course. It passes all my tests, but it really needs an implementation from a professional mathematician. Maybe you can file this with other feature requests you have received. An excerpt from my code follows below. I hope I have understood lists correctly that they are doubly linked and a list append of one element runs in constant time. Best regards, Marko lst factorizeposint(numeric n) { lst result = {}, ent; int pot = 0; while(irem(n, numeric(2)).is_zero()){ pot++; n = iquo(n, numeric(2)); } if(pot > 0){ ent = {numeric(2), pot}; result.append(ent); } numeric q = 3; while(q*q <= n){ pot = 0; while(irem(n, q).is_zero()){ pot++; n = iquo(n, q); } if(pot > 0){ ent = {q, pot}; result.append(ent); } q += 2; } if(n > 1){ ent = {n, numeric(1)}; result.append(ent); } return result; } numeric totient(numeric n) { if(n==1) return 1; lst pfact = factorizeposint(n); numeric result = n; for(lst::const_iterator it = pfact.begin(); it != pfact.end(); ++it){ lst ent = ex_to<lst>(*it); result *= numeric(1) -numeric(1)/ex_to<numeric>(ent.op(0)); } return result; } lst divisors(numeric n) { if (n==1) return {1}; lst pfact = factorizeposint(n), ent; numeric tau(1); lst::const_iterator it; for(it = pfact.begin(); it != pfact.end(); ++it){ ent = ex_to<lst>(*it); tau *= numeric(1)+ex_to<numeric>(ent.op(1)); } exvector res {}; res.resize(tau.to_int(), numeric(1)); int sofar = 1; int pos; for(it = pfact.begin(); it != pfact.end(); ++it){ pos = sofar; ent = ex_to<lst>(*it); numeric p = ex_to<numeric>(ent.op(0)); numeric v = ex_to<numeric>(ent.op(1)); for(numeric vv(1); vv <= v; vv++){ for(int q = 0; q < sofar; q++){ res[pos++] = res[q]*pow(p,vv); } } sofar = pos; } lst result = {}; for(pos=0; pos<sofar; pos++) result.append(res[pos]); return result; }

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Adding custom functions to the parser
by Vitaly Magerya 20 Feb '23

20 Feb '23

Hi, all. I'm trying to add custom functions to GiNaC::parser in a way similar to how it's done in default_reader.cpp: #include <ginac/ginac.h> #include <ginac/parser.h> #include <iostream> #include <sstream> #include <string> static GiNaC::ex sqrt_reader(const GiNaC::exvector& ev) { return GiNaC::sqrt(ev[0]); } int main() { std::string input = "sqrt(4)"; std::istringstream instream(input); auto proto = GiNaC::prototype_table(); proto[std::make_pair("sqrt", 1)] = sqrt_reader; auto symtab = GiNaC::symtab(); auto reader = GiNaC::parser(symtab, false, proto); GiNaC::ex expr = reader(instream); std::cout << input << " = " << expr << "\n"; } This unfortunately crashes before entering sqrt_reader. Here's a backtrace: #0 GiNaC::function::eval (this=0x7fffffffcd10) at function.cpp:1450 #1 0x000000000045c212 in GiNaC::ex::construct_from_basic (other=...) at ex.cpp:309 #2 0x000000000059e0d5 in GiNaC::ex::ex (other=..., this=0x7fffffffcc50) at ./ex.h:268 #3 GiNaC::dispatch_reader_fcn (args=std::vector of length 1, capacity 1 = {...}, ptr=<optimized out>) at parser/parser.cpp:62 #4 GiNaC::parser::parse_identifier_expr (this=<optimized out>) at parser/parser.cpp:103 #5 0x000000000059db7d in GiNaC::parser::parse_primary (this=this@entry=0x7fffffffd310) at parser/parser.cpp:173 #6 0x000000000059dc3f in GiNaC::parser::parse_expression (this=this@entry=0x7fffffffd310) at parser/parser.cpp:194 #7 0x000000000059e919 in GiNaC::parser::operator() (this=0x7fffffffd310, input=...) at parser/parser.cpp:226 #8 0x0000000000423e35 in main () at parsingcrash.cpp:21 Can anyone tell me how to do this correctly?

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GiNaC::parser parses "3^+2+1" in the wrong order
by Vitaly Magerya 20 Feb '23

20 Feb '23

Hi, all. When parsing expressions with sign in the exponent, GiNaC's parses confuses the priorities somehow. Here are some examples: 3^2+1 is parsed as (3^2)+1, which is correct; 3^+2+1 is parsed as 3^(+2+1), which is wrong; 3^-2+1 is parsed as 3^(-2+1), which is wrong; 3^+2/3 is parsed as 3^(+2/3), which is wrong; etc. Here's a test case, it will print 27, not the correct 10: #include <ginac/ginac.h> #include <ginac/parser.h> #include <iostream> #include <sstream> #include <string> int main() { std::string input = "3^+2+1"; std::istringstream instream(input); GiNaC::parser reader; GiNaC::ex expr = reader(instream); std::cout << input << " = " << expr << "\n"; }

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type casting
by Marko Riedel 12 Feb '23

12 Feb '23

Hi all, I have a set of custom objects that is declared like this: struct cindsym_is_less { bool operator() (const cindsymbol &lh, const cindsymbol &rh) const { return lh.compare(rh) < 0; } }; typedef std::set<cindsymbol, cindsym_is_less> cindsymset; Now I want to collect all custom objects that appear in an expression tree into this kind of set. I tried this: void indets_recurse(ex src, cindsymset & coll) { if(is_a<add>(src) || is_a<mul>(src) || is_a<power>(src)){ for(size_t idx = 0; idx < src.nops(); idx++) indets_recurse(src.op(idx), coll); return; } if(is_a<cindsymbol>(src)){ coll.insert(src); } } However this will produce the error "no matching function call" because src is an expression and not a cindsymbol. I know that I have my kind of symbol because is_a<cindsymbol> returned true. How can I get at the symbol wrapped in the expression? Best regards, Marko

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symbol equality
by Marko Riedel 09 Feb '23

09 Feb '23

Greetings to all. I have been subclassing "symbol" for my project, where I need to attach an integer value to a symbol. I am not sure this is the best way to go about it but I would like to try. Everything works so far but now I have moved on to substituting variables in polynomials. Here is my sample program. #include <iostream> #include <ginac/ginac.h> #include "cindsymbol.h" #include "util.h" using namespace std; using namespace GiNaC; int main() { cindsymbol R = cindsymbol("R",0), G = cindsymbol("G",0), B = cindsymbol("B",0), X = cindsymbol("X",0); ex pl = X + pow(X, 3) + R + G + B; cout << R << G << B << " " << pl << endl; cout << pl.subs({X}, {pow(X,4)}) << endl; return 0; } The output of this program is as follows (the print functions from the subclass are being invoked correctly and do not print the zero value): RGB X+R+G+B+X^3 4*X^4+X^12 Obviously GiNaC thinks that R=X, B=X and G=X. How do I get this comparison to work? Do I need to override some function in my subclass? The function "cindsymbol" goes as follows (copied from the tutorial): static map<string, cindsymbol> directory; cindsymbol cindsym(const std::string & initname, unsigned cl) { std::string key = initname + "|" + std::to_string(cl); map<std::string, cindsymbol>::iterator it = directory.find(key); if (it != directory.end()) return it->second; else{ std::pair<std::string, cindsymbol> ent = make_pair(key, cindsymbol(initname, cl)); return directory.insert(ent).first->second; } } Can you advise me here? Thanks! Best regards, Marko Riedel

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GiNaC 1.8.6 released
by Richard B. Kreckel 09 Feb '23

09 Feb '23

Hi, GiNaC 1.8.6 has been tagged and released. The News: * Fix wrong numeric info on transcendental functions. * Fix crash of evaluation of binomial(n, k) with negative integer n, k. Happy hacking! -richy. PS: If anyone knows how to push a commit together with the tags using git, do let me know. Yes, I've googled it up and tried several things but it never worked. -- Richard B. Kreckel <https://in.terlu.de/~kreckel/>

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