Hi,: I am trying to introduce symbolic functions in a numeric fem code. To do that I want to store expressions (functions) inside a class. I read outside the class a string with the function (example, sin(t) ), then I create an object for store it. I use the constructor to pass the string. In the constructor I create the expression, and I intend to use it later (with the valor function), but in the constructor I always get a segmentation fault when I call the ex constructor. It must be something obvious but I am unable to find it. I have tried to debug with gdb and put a try--catch group but I have not found the explanation of the segmentation fault error. The code I am using to test it is as follows: ========================================================================= #include<iostream.h> #include<ginac/ginac.h> #include<ginac/lst.h> using namespace std; using namespace GiNaC; class fext { public: string funcionstr; ex funcion ; symbol tiempo ; lst l ; public: fext (string &); // Constructor double valor(double); }; fext::fext (string & funcionc) { funcionstr = string(funcionc) ; tiempo = symbol("t") ; funcion = ex(funcionstr,lst(tiempo)) ; } double fext::valor(double tt) { return( ex_to<numeric>(funcion.subs(tiempo==tt)).to_double() ) ; } int main() { string st ; cin >> st ; fext fexx = fext(st) ; cout << "\n input t-value " ; double valorcillo ; cin >> valorcillo ; cout << "\n fexx value" << fexx.valor(valorcillo) ; } ================================================================= I am using debian-linux (woody) with the following versions: ginac-config --version 1.0.8 g++ -v Reading specs from /usr/lib/gcc-lib/i386-linux/2.95.4/specs gcc version 2.95.4 20011006 (Debian prerelease) To compile it I use g++ prusimple.cc -o prusimple -lginac -lcln Thanks in advance for any idea. Juan Jose Arribas Mechanics Department Civil Engineers School Politechnic University Madrid Spain