What is wrong with this C++ class? [closed] - c++

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Here is the code that I have so far:
#include <iostream>
using namespace std;
class Rectangle
{
private:
double width, height;
public:
Rectangle();
double Set(double x, double y);
double getArea();
double getPerimeter();
};
Rectangle::Rectangle()
{
width = 1;
height = 1;
}
double Rectangle::Set(double x, double y)
{
width = x;
height = y;
}
double Rectangle::getArea()
{
double area = height * width;
return area;
}
double Rectangle::getPerimeter()
{
double perimeter = (width * 2) + (height * 2);
return perimeter;
}
int main()
{
double width, height;
cout << "Enter the width and height of a rectangle:";
cin >> width >> height;
cout << "The area is " << Rectangle::getArea << " and the perimeter is " << Rectangle::getPerimeter << endl;
}
When running this code I get the error : "'Rectangle::getArea': non-standard syntax; use '&' to create a pointer to member"
I get the same error about the Rectangle::getPerimeter
I am not sure what the problem is, I am new to making classes in C++ obviously, so I am having some trouble. Any suggestions?

Answer 1

There are several problems with your code.
1.) You never instantiate the class (i.e. create an object of that class type.) Having two variables with the names width and height is not the same as having an object of the type Rectangle.
2.) You are trying to call a non-static member function as if they were static member functions. Member functions are called via objects, for example
rect.getArea() where rect is an object of the type Rectangle.
3.) You are missing the parentheses at the function call. Whenever you get the message non-standard syntax, use & to create a pointer to a member it usually means that you have forgotten the parentheses at a function call.
What you want is probably something like:
int main()
{
double width, height;
cout << "Enter the width and height of a rectangle:";
cin >> width >> height;
Rectangle rect;
rect.Set(width, height);
cout << "The area is " << rect.getArea() << " and the perimeter is " << rect.getPerimeter() << endl;
}

Answer 2

1st create the object of Rectangle() class and then call the respective methods.
Rectangle rect;/* object of rectangle class */
your main() looks like
int main() {
double width, height;
cout << "Enter the width and height of a rectangle:";
cin >> width >> height;
Rectangle rect;/* object of rectangle class */
/* calling set method and passing the parameter */
rect.Set(width,height);
cout << "The area is " << rect.getArea() << " and the perimeter is " << rect.getPerimeter() << endl;
return 0;
}
As If i understood correctly you don't need Set() method actually, instead of this you do the same stuff using constructor by passing parameters.
parameterized constructor instead of Set() method
Rectangle::Rectangle(double x, double y) {
width = x;
height = y;
}
And create objects like
Rectangle rect(width,height);/* it will be called automatically */

Answer 3

For starters this member function returns nothing
double Rectangle::Set(double x, double y)
{
width = x;
height = y;
}
So it should be defined like
void Rectangle::Set(double x, double y)
{
width = x;
height = y;
}
It seems you mean
//...
cin >> width >> height;
Rectangle r;
r.Set( width, height );
cout << "The area is " << r.getArea() << " and the perimeter is " << r.getPerimeter() << endl;
The functions getArea and getPerimeter should be declared as constant member functions
double getArea() const;
double getPerimeter() const;
because they do not change objects of the type Rectangle.
It would be logical consistent if the class had a constructor with two parameters
Rectangle( double width, double height );
And the method Set should be split into two methods like setWidth and setHeight.