#include 
     
      #include 
      
       using namespace Eigen;using namespace std;int main(){#pragma  region  Addition and subtraction	Matrix2d a;	a << 1, 2,		3, 4;	MatrixXd b(2, 2);	b << 2, 3,		1, 4;	std::cout << "a + b =n" << a + b << std::endl;	std::cout << "a - b =n" << a - b << std::endl;	std::cout << "Doing a += b;" << std::endl;	a += b;	std::cout << "Now a =n" << a << std::endl;	Vector3d v(1, 2, 3);	Vector3d w(1, 0, 0);	std::cout << "-v + w - v =n" << -v + w - v << std::endl;#pragma endregion#pragma  region  Scalar multiplication and division//	Matrix2d a;  //duplicate definition	a << 1, 2,		3, 4;//	Vector3d v(1, 2, 3);   //duplicate definition	std::cout << "a * 2.5 =n" << a * 2.5 << std::endl;	std::cout << "0.1 * v =n" << 0.1 * v << std::endl;	std::cout << "Doing v *= 2;" << std::endl;	v *= 2;	std::cout << "Now v =n" << v << std::endl;#pragma endregion#pragma  region  Transposition and conjugation	MatrixXcf a_matrix = MatrixXcf::Random(2, 2);	cout << "Here is the matrix a_matrixn" << a_matrix << endl;	cout << "Here is the matrix a_matrix^Tn" << a_matrix.transpose() << endl;	cout << "Here is the conjugate of a_matrixn" << a_matrix.conjugate() << endl;	cout << "Here is the matrix a_matrix^*n" << a_matrix.adjoint() << endl;	//This is the so-called aliasing issue	Matrix2i a_matrix2; 	a_matrix2 << 1, 2, 3, 4;	cout << "Here is the matrix a_matrix2:n" << a_matrix2 << endl;	// a_matrix2 = a_matrix2.transpose(); // !!! do NOT do this !!!	cout << "and the result of the aliasing effect:n" << a_matrix2 << endl;#pragma endregion#pragma  region  Matrix-matrix and matrix-vector multiplication	Matrix2d mat;	mat << 1, 2,		3, 4;	Vector2d u_1(-1, 1), v_1(2, 0);	std::cout << "Here is mat*mat:n" << mat * mat << std::endl;	std::cout << "Here is mat*u_1:n" << mat * u_1 << std::endl;	std::cout << "Here is u_1^T*mat:n" << u_1.transpose()*mat << std::endl;	std::cout << "Here is u_1^T*v:n" << u_1.transpose()*v_1 << std::endl;	std::cout << "Here is u_1*v_1^T:n" << u_1 * v_1.transpose() << std::endl;	std::cout << "Let's multiply mat by itself" << std::endl;	mat = mat * mat;	std::cout << "Now mat is mat:n" << mat << std::endl;#pragma endregion  #pragma  region  Dot product and cross product	Vector3d v_2(1, 2, 3);	Vector3d w_2(0, 1, 2);	cout << "Dot product: " << v_2.dot(w_2) << endl;	double dp = v_2.adjoint()*w_2; // automatic conversion of the inner product to a scalar	cout << "Dot product via a matrix product: " << dp << endl;	cout << "Cross product:n" << v_2.cross(w_2) << endl;#pragma endregion#pragma region   Basic arithmetic reduction operations	Eigen::Matrix2d mat_3;	mat_3 << 1, 2,		3, 4;	cout << "Here is mat_3.sum():       " << mat_3.sum() << endl;	cout << "Here is mat_3.prod():      " << mat_3.prod() << endl;	cout << "Here is mat_3.mean():      " << mat_3.mean() << endl;	cout << "Here is mat_3.minCoeff():  " << mat_3.minCoeff() << endl;	cout << "Here is mat_3.maxCoeff():  " << mat_3.maxCoeff() << endl;	cout << "Here is mat_3.trace():     " << mat_3.trace() << endl;	Matrix3f m = Matrix3f::Random();	std::ptrdiff_t i, j;	float minOfM = m.minCoeff(&i, &j);	cout << "Here is the matrix m:n" << m << endl;	cout << "Its minimum coefficient (" << minOfM		<< ") is at position (" << i << "," << j << ")nn";	RowVector4i v_4 = RowVector4i::Random();	int maxOfV = v_4.maxCoeff(&i);	cout << "Here is the vector v_4: " << v_4 << endl;	cout << "Its maximum coefficient (" << maxOfV		<< ") is at position " << i << endl;#pragma endregion/**************This is the end of example codes in Eigen3 online document. **********************/    system("pause");}