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| #include <Eigen/Core>
| #include <iostream>
| using namespace Eigen;
| using namespace std;
|
| template<typename Derived>
| Eigen::Block<Derived, 2, 2>
| topLeft2x2Corner(MatrixBase<Derived>& m)
| {
| return Eigen::Block<Derived, 2, 2>(m.derived(), 0, 0);
| }
|
| template<typename Derived>
| const Eigen::Block<const Derived, 2, 2>
| topLeft2x2Corner(const MatrixBase<Derived>& m)
| {
| return Eigen::Block<const Derived, 2, 2>(m.derived(), 0, 0);
| }
|
| int main(int, char**)
| {
| Matrix3d m = Matrix3d::Identity();
| cout << topLeft2x2Corner(4*m) << endl; // calls the const version
| topLeft2x2Corner(m) *= 2; // calls the non-const version
| cout << "Now the matrix m is:" << endl << m << endl;
| return 0;
| }
|
|