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a question about operator *= function

alirah84 (42)
It's a program about operator function(*=).
Question:
Declare a class for Rectangle and Declare a class for Triangle.So compute area of this two and Declare a operator *= function that it multiplies area of triangle and rectangle and place value in triangle object.
I wrote this incomplete.Why should we write operator *= function in triangle class? In triangle class ,we don't access to rectangle area.plz help me.
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#include <iostream>
#include <string>
using namespace std;
class triangle;
class rect
{
int x,y,s1;
public:
	void input();
	int calc();
};
void rect::input()
{
	cout<<"Enter Area:";
	cin>>x>>y;
}
int rect::calc()
{
	return s1=x*y;
}
class rect;
class triangle 
{
	int a,h,s2;
public:
	void input();
	int calc();
};
void triangle::input()
{
	cout<<"Enter Base and height";
	cin>>a>>h;
}
int triangle::calc()
{
	return s2=(a*h)/2;
}
triangle triangle::operator *=(rect o2)
int main()
{
	triangle o1;
	rect o2;
	o1.input();
	o1.calc();
	o2.input();
	o2.calc();
	o1*=o2;
}
Last edited on
Stewbond (2827)
Why can't triangle access the area of the rect? Just implement a "getter"

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#include <iostream>

class poly
{
private: 
    virtual void calc_area() = 0;
protected:
    double m_base;
    double m_height;
    double m_area;
public:
    double get_area() { return m_area; }
    
    poly( double base, double height )
        : m_base(base), m_height(height)
    {}
};

class rect : public poly
{
private:
    virtual void calc_area() 
    { 
        m_area = m_base * m_height; 
    }
public:
    rect ( double base, double height) 
        : poly(base,height) 
    {
        calc_area();
    }
};

class triangle : public poly
{
private:
    virtual void calc_area()
    {
        m_area = 0.5 * m_base * m_height;
    }
public: 
    triangle (double base, double height)
        : poly(base,height) 
    {
        calc_area();
    }

    double operator*= (rect& r)
    {
        m_area *= r.get_area();
        m_base = 2 * m_area / m_height;
        return m_area;
    }
};

int main()
{
    rect r(1,2);
    triangle t(3,4);

    std::cout << r.get_area() << std::endl;
    std::cout << t.get_area() << std::endl;
    std::cout << (t *= r)     << std::endl;
}
 
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Press any key to continue . . .
Last edited on
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