#include <expression.h>

 #include <iostream>

 #include <string>

 using std::cout;

 using std::endl;

 using std::string;

 using namespace lemon;

 int main() {

   Expr<string, double> b;

   cout << b << endl;

   Expr<string, double> c("f");

   cout << c << endl;

   Expr<string, double> d=8.0*string("g");

   cout << d << endl;

   c*=5;

   cout << c << endl;

   Expr<string, double> e=c;

   e+=8.9*9.0*string("l");

   cout << e << endl;

   cout << c+d << endl;

 }