Help with Error 'cannot bind'

[LemonHappy]

I keep getting this error:
cannot bind 'std::ostream {aka std::basic_ostream<char>}' lvalue to 'std::basic_ostream<char>&&'

#include <iostream>
using namespace std;

class Square {
	
   private:
      double side;
     
      
   public:

      double getArea() {
         return side * side;
      }
		
      void setSide( double s ) {
         side = s;
      }

     
     
		
      // Overload + operator to add two Square objects.
      Square operator+(const Square& b) {
         Square square;
         square.side = side + b.side;
         return square;
      }
      
        Square operator-(const Square& b) {
         Square square;
         square.side = side - b.side;
         return square;
    }
        
        
         Square operator*(const Square& b) {
         Square square;
         square.side = side * b.side;
         return square;
         
         }
         
         Square operator/(const Square& b) {
         Square square;
         square.side = side / b.side;
         return square;
      }
    };

// Main function
int main( ) {
   Square Square1;                
   Square Square2;                
   Square Square3; 
   
   double area = 0.0;     
 
   
   Square1.setSide(2.0);
   
   Square2.setSide(5.0);
 
   
   // Square1 area
   area = Square1.getArea();
   cout << "Area of Square1 : " << area <<endl;
 
   // Square2 area
   area = Square2.getArea();
   
   cout << "Area of Square2 : " << area <<endl;

      char op;
  
    cout << "Enter the operator: ";
    cin >> op;
    switch (op)
    {
    case '+':
        Square3 = Square1 + Square2;
        cout << Square3;
        break;
    case '-':
        Square3 = Square1 - Square2;
        cout << Square3;
        break;
    case '*':
        Square3 = Square1 * Square2;
        cout << Square3;
        break;
    default:
        cout << "No a valid operator";
    }
   return 0;
}

[lastchance]

The operator << hasn't been defined for a Square object (lines 82 etc.)

Either define it within the Square class, or cout whatever specific things about Square3 you actually intended (its area, maybe?)

[LemonHappy]

Ok, so how would I Display Square3. I want to display the new value of the square from for example Square1 + Square2 which is in the first case. How would I define it in Square?

[lastchance]

Square is a type of object. What exactly are you trying to display about Square3? Its side length? Its area?

If you want to write out its area then just use
cout << Square3.getArea();
in lines 82, 86, 90.

[lastchance]

I guess this is what you are asking for:

#include <iostream>
using namespace std;

class Square {
        
   private:
      double side;
     
      
   public:

      double getArea() {
         return side * side;
      }
                
      void setSide( double s ) {
         side = s;
      }

     
     
                
      // Overload + operator to add two Square objects.
      Square operator+(const Square& b) {
         Square square;
         square.side = side + b.side;
         return square;
      }
      
        Square operator-(const Square& b) {
         Square square;
         square.side = side - b.side;
         return square;
    }
        
        
         Square operator*(const Square& b) {
         Square square;
         square.side = side * b.side;
         return square;
         
         }
         
         Square operator/(const Square& b) {
         Square square;
         square.side = side / b.side;
         return square;
      }


      // This line needed to get at any private variables for a Square (e.g. side)
      friend ostream &operator<<( ostream &stream, Square sq );
    };


// An operator to << a square
ostream &operator<<( ostream &stream, Square sq )
{
   stream << "The user still hasn't said what he wants, so ...\n";
   stream << "... HERE'S A SQUARE!!!\n";
   stream << endl;
   stream << "       *******\n";
   stream << "       *     *\n";
   stream << "       *     *  " << "Side length: " << sq.side      << endl;
   stream << "       *     *\n";
   stream << "       *     *  " << "Area       : " << sq.getArea() << endl;
   stream << "       *     *\n";
   stream << "       *******\n";
   stream << endl;

   return stream;
}



// Main function
int main( ) {
   Square Square1;                
   Square Square2;                
   Square Square3; 
   
   double area = 0.0;     
 
   
   Square1.setSide(2.0);
   
   Square2.setSide(5.0);
 
   
   // Square1 area
   area = Square1.getArea();
   cout << "Area of Square1 : " << area <<endl;
 
   // Square2 area
   area = Square2.getArea();
   
   cout << "Area of Square2 : " << area <<endl;

      char op;
  
    cout << "Enter the operator: ";
    cin >> op;
    switch (op)
    {
    case '+':
        Square3 = Square1 + Square2;
        cout << Square3;
        break;
    case '-':
        Square3 = Square1 - Square2;
        cout << Square3;
        break;
    case '*':
        Square3 = Square1 * Square2;
        cout << Square3;
        break;
    default:
        cout << "No a valid operator";
    }
   return 0;
}