On Sun, 01 Mar 2015 13:07:15 +0100, "Richard B. Kreckel" <kreckel@in.terlu.de> said:
RK> On 03/01/2015 12:25 PM, soppon wrote: >> #include <iostream> #include <ginac/ginac.h> using namespace std; >> using namespace GiNaC; >> >> int main() { symbol xs("x"); lst expr; parser reader; >> expr=reader("{x,x}"); cout <<"list " << expr << endl; cout >> <<"number of elements "<< expr.nops() << endl; cout <<"1st el " >> <<expr[0] << endl; cout <<"2nd el, error " <<expr[1]<< endl; >> return 0; } RK> Your list expr has only one element, which is itself a list with RK> two elements. As was already suggested, a plain list may be obtained by: expr=ex_to<lst>(reader("{x,x}")); -- Vladimir V. Kisil http://www.maths.leeds.ac.uk/~kisilv/ Book: Geometry of Mobius Transformations http://goo.gl/EaG2Vu Software: Geometry of cycles http://moebinv.sourceforge.net/