std::ostringstream buf;

     //Checking the simplify function

 //     //How to check the simplify function? A map gives no information

 //     //on the question whether a given key is or is not stored in it, or

 //     //it does?

 //   Yes, it does, using the find() function.

     e=((p1+p2)+(p1-p2));

     e.simplify();

     buf << "Coeff. of p2 should be 0";

     //    std::cout<<e[p1]<<e[p2]<<e[p3]<<std::endl;

     check(e.find(p2)==e.end(), buf.str());

     e=((p1+p2)+(p1-0.99*p2));

     double tolerance=0.001;

     e.simplify(tolerance);

     buf << "Coeff. of p2 should be 0.01";

     check(e[p2]>0, buf.str());

     tolerance=0.02;

     e.simplify(tolerance);

     buf << "Coeff. of p2 should be 0";

     check(e.find(p2)==e.end(), buf.str());