Function insertCoefficient

doc/special_examples/Tutorial_sparse_example_details.cpp:8–17

typedef Eigen::Triplet<double> T;

void insertCoefficient(int id, int i, int j, double w, std::vector<T>& coeffs,
                       Eigen::VectorXd& b, const Eigen::VectorXd& boundary)
{
  int n = int(boundary.size());
  int id1 = i+j*n;

        if(i==-1 || i==n) b(id) -= w * boundary(j); // constrained coefficient
  else  if(j==-1 || j==n) b(id) -= w * boundary(i); // constrained coefficient
  else  coeffs.push_back(T(id,id1,w));              // unknown coefficient
}

void buildProblem(std::vector<T>& coefficients, Eigen::VectorXd& b, int n)
{