Hello, thanks but I resolve the former problem...besides I have a new one

now the expresion ex that is well casted from the string is not well transformed into a derivative with diff

parser reader;
e = reader(ramaPrim[i]);

cout<<"ex="<<e<<" diff:"<<e.diff(r).subs(r==Pi)<< " i="<<i<<endl;

e is well printed and is a function of r but its derivative is cero!

What is happening here

Thanks