#include <triqs/det_manip/det_manip.hpp>
    
    struct fun {
      
      typedef double result_type;
      typedef double argument_type;
      
      //gives the coefficients of the matrix (function F of the documentation)
      double operator()(double x, double y) const {
        return (x-y+1)*(x-y);
      }
      
    };
    
    int main() {
     try { 
      fun f;
      int init_size=10;
      std::vector<double> initial_x{1,2,2.5}, initial_y{3,4,9};
      
      //creation of an empty class det_manip
      triqs::det_manip::det_manip<fun> D1(f, init_size);
      
      //creation of a class det_manip with a 3 by 3 matrix
      triqs::det_manip::det_manip<fun> D2(f, initial_x, initial_y);
      
      //the initial matrix:
      std::cout<<std::endl<< "After construction: D.matrix()=" << D1.matrix()<<std::endl;
      std::cout<<std::endl<< "After construction: D.matrix()=" << D2.matrix()<<std::endl;
     }
     catch(std::exception const & e ) { std::cout  << "error "<< e.what()<< std::endl;}
    }