ADD: new track message, Entity class and Position class

libs/eigen/doc/examples/CustomizingEigen_Inheritance.cpp

@@ -0,0 +1,30 @@
+#include <Eigen/Core>
+#include <iostream>
+
+class MyVectorType : public Eigen::VectorXd
+{
+public:
+    MyVectorType(void):Eigen::VectorXd() {}
+
+    // This constructor allows you to construct MyVectorType from Eigen expressions
+    template<typename OtherDerived>
+    MyVectorType(const Eigen::MatrixBase<OtherDerived>& other)
+        : Eigen::VectorXd(other)
+    { }
+
+    // This method allows you to assign Eigen expressions to MyVectorType
+    template<typename OtherDerived>
+    MyVectorType& operator=(const Eigen::MatrixBase <OtherDerived>& other)
+    {
+        this->Eigen::VectorXd::operator=(other);
+        return *this;
+    }
+};
+
+int main()
+{
+  MyVectorType v = MyVectorType::Ones(4);
+  v(2) += 10;
+  v = 2 * v;
+  std::cout << v.transpose() << std::endl;
+}