improvements in tutorial page 4 : block operations

doc/examples/Tutorial_BlockOperations_colrow.cpp

@@ -1,14 +1,17 @@
 #include <Eigen/Dense>
 #include <iostream>
 
+using namespace std;
+
 int main()
 {
   Eigen::MatrixXf m(3,3);
   m << 1,2,3,
        4,5,6,
        7,8,9;
-  std::cout << "2nd Row: " << m.row(1) << std::endl;
-  m.col(0) += m.col(2);
-  std::cout << "m after adding third column to first:\n";
-  std::cout << m << std::endl;
+  cout << "Here is the matrix m:" << endl << m << endl;
+  cout << "2nd Row: " << m.row(1) << endl;
+  m.col(2) += 3 * m.col(0);
+  cout << "After adding 3 times the first column into the third column, the matrix m is:\n";
+  cout << m << endl;
 }