1 files changed, 27 insertions, 0 deletions
diff --git a/eigen/doc/examples/class_Block.cpp b/eigen/doc/examples/class_Block.cpp
new file mode 100644
index 0000000..ace719a
--- /dev/null
+++ b/eigen/doc/examples/class_Block.cpp
@@ -0,0 +1,27 @@
+#include <Eigen/Core>
+#include <iostream>
+using namespace Eigen;
+using namespace std;
+
+template<typename Derived>
+Eigen::Block<Derived>
+topLeftCorner(MatrixBase<Derived>& m, int rows, int cols)
+{
+  return Eigen::Block<Derived>(m.derived(), 0, 0, rows, cols);
+}
+
+template<typename Derived>
+const Eigen::Block<const Derived>
+topLeftCorner(const MatrixBase<Derived>& m, int rows, int cols)
+{
+  return Eigen::Block<const Derived>(m.derived(), 0, 0, rows, cols);
+}
+
+int main(int, char**)
+{
+  Matrix4d m = Matrix4d::Identity();
+  cout << topLeftCorner(4*m, 2, 3) << endl; // calls the const version
+  topLeftCorner(m, 2, 3) *= 5;              // calls the non-const version
+  cout << "Now the matrix m is:" << endl << m << endl;
+  return 0;
+}