C++ namespace has no member

C++ namespace has no member

#include <iostream>
#include<fstream>
#include<math.h>

using namespace std;

class Shape
{
private:
	string color;
	string name;

public:

	Shape()
	{
		color = "";
		name = "";
	}

	Shape(string col, string nm)
	{
		color = col;
		name = nm;
	}
	void setColor(string col)
	{
		cout << "Color:" << color << endl;
		color = col;

	}
	void setName(string nm)
	{
		name = nm;
	}
	void print()
	{
		cout << "Color:" << color << endl;
		cout << "Name:" << name << endl;
	}
	void readData(string col, string nm)
	{
		cout << "readdata Shape" << col << endl;
		setColor(col);
		setName(nm);

	}
	void printToFile(ofstream& output)
	{
		output << color << "," << name << ",";
	}
	virtual void readFromFile(ifstream& input) = 0;


};

class Shape2D :public Shape
{
protected:
	double perimeter;
	double area;

public:
	Shape2D()
	{
		perimeter = 1.0;
		area = 1.0;
	}
	Shape2D(string col, string nm) :Shape(col, nm)
	{
		cout << "param constructor" << endl;
		perimeter = 1.0;
		area = 1.0;
	}
	double getPerimeter() { return perimeter; }
	double getArea() { return area; }
	void setArea(double val)
	{
		area = val;

	}
	void setPerimeter(double val)
	{
		perimeter = val;
	}
	void print()
	{
		Shape::print();
		cout << "Perimeter:" << perimeter << endl;
		cout << "Area:" << area << endl;
	}
	void readData(string col, string nm)
	{
		cout << "Read data Shape2D" << endl;
		setColor(col);
		setName(nm);
		return;
	}
	void printToFile(ofstream& output)
	{
		Shape::printToFile(output);
	}
	virtual void computeArea() = 0;
	virtual void computePerimeter() = 0;
	virtual void readFromFile(ifstream& input) = 0;

};

class Square :public Shape2D
{
private:
	double length;
public:

	Square()
	{
		length = 1.0;
	}
	Square(string col, string nm, double lem) :Shape2D(col, nm)
	{
		length = lem;
	}
	void computeArea()
	{
		setArea(length * length);
	}
	void computePerimeter()
	{
		setPerimeter(4 * length);
	}
	void print()
	{
		Shape2D::print();
	}
	void readData(string col, string nm, double lem)
	{
		length = lem;
		Shape2D::readData(col, nm);
		return;
	}
	void printToFile(ofstream& output)
	{
		Shape::printToFile(output);
		output << length << "," << getArea() << "," << getPerimeter() << "\n";
	}
	void readFromFile(ifstream& input)
	{
		string data = "";
		while (std::getline(input, data))
		{
			std::cout << data << endl;
		}
	}
};

class Triangle :public Shape2D
{
private:
	double length;
public:
	Triangle()
	{
		length = 1.0;
	}
	Triangle(string col, string nm, double lem) :Shape2D(col, nm)
	{
		length = lem;
	}
	void computeArea()
	{
		setArea(0.433 * length * length);
	}
	void computePerimeter()
	{
		setPerimeter(3 * length);
	}
	void print()
	{
		Shape2D::print();
	}
	void readData(string col, string nm, double lem)
	{
		cout << "Read data triangle" << endl;
		Shape2D::readData(col, nm);
		length = lem;
		return;
	}
	void printToFile(ofstream& output)
	{
		Shape::printToFile(output);
		output << length << "," << getArea() << "," << getPerimeter() << "\n";
	}
	void readFromFile(ifstream& input)
	{
		string data = "";
		while (std::getline(input, data))
		{
			std::cout << data << endl;
		}
	}
};

class Hexagon :public Shape2D
{
private:
	double length;
public:
	Hexagon()
	{
		length = 1.0;
	}
	Hexagon(string col, string nm, double lem) :Shape2D(col, nm)
	{
		length = lem;
	}
	void computeArea()
	{
		setArea((3 * sqrt(3) * pow(length, 2)) / 2.0);
	}
	void computePerimeter()
	{
		setPerimeter(6 * length);
	}
	void setLength(double len)
	{
		cout << "settingb length set" << endl;
		length = len;
	}
	void print()
	{
		Shape2D::print();
	}
	void readData(string col, string nm, double lem)
	{
		cout << "Read data hexagon:" << col << "\t" << nm << "\t" << lem << endl;
		setLength(lem);
		cout << "length set" << endl;
		setColor(col);
		setName(nm);

		return;
	}
	void printToFile(ofstream& output)
	{
		Shape::printToFile(output);
		output << length << "," << getArea() << "," << getPerimeter() << "\n";
	}
	void readFromFile(ifstream& input)
	{
		string data = "";
		while (std::getline(input, data))
		{
			std::cout << data << endl;
		}
	}
};

int main()
{
	ofstream myfile;
	myfile.open("Shapes.dat");
	Square* obj = new Square("Blue", "Square", 4.0);
	obj->computeArea();
	obj->computePerimeter();
	obj->print();
	obj->printToFile(myfile);



	Triangle* obj2 = new Triangle("Yellow", "Triangle", 12.0);
	obj2->computeArea();
	obj2->computePerimeter();
	obj2->print();
	obj2->printToFile(myfile);

	Hexagon obj3;
	string col, name;
	double length;
	cout << "Enter color,name,length of hexagon" << endl;
	cin >> col;
	cin >> name;
	cin >> length;
	obj3.readData(col, name, length);
	obj3.computeArea();
	obj3.computePerimeter();
	obj3.print();
	obj3.printToFile(myfile);

	myfile.close();

	std::ifstream file;
	file.open("Shapes.dat");
	obj3.readFromFile(file);
	return 0;
}