ADD: added other eigen lib

libs/eigen/doc/examples/TutorialLinAlgExSolveLDLT.cpp

@@ -1,16 +1,13 @@
 #include <iostream>
 #include <Eigen/Dense>
 
-using namespace std;
-using namespace Eigen;
-
 int main()
 {
-   Matrix2f A, b;
+   Eigen::Matrix2f A, b;
    A << 2, -1, -1, 3;
    b << 1, 2, 3, 1;
-   cout << "Here is the matrix A:\n" << A << endl;
-   cout << "Here is the right hand side b:\n" << b << endl;
-   Matrix2f x = A.ldlt().solve(b);
-   cout << "The solution is:\n" << x << endl;
+   std::cout << "Here is the matrix A:\n" << A << std::endl;
+   std::cout << "Here is the right hand side b:\n" << b << std::endl;
+   Eigen::Matrix2f x = A.ldlt().solve(b);
+   std::cout << "The solution is:\n" << x << std::endl;
 }