problem in inheritence

[BotoolZyoud]

erorr in child class.
Error 1 error C2512: 'Circle_computations' : no appropriate default constructor available
Error 4 error C2296: '*' : illegal, left operand has type 'void'

  #include<iostream>
using namespace std;

class Circle_computations
{

public:
	double area,circumference,radius,pi;
	
public:
	
  Circle_computations(double radi)
{
pi = 3.14;
radius=radi;


}

void c_area()
{

area = pi*radius*radius;
 // cout<<"****The  Area OF The Circle  is****\n"<<area<<"\n";

}

void c_circumferunce()
{

circumference =2*pi*radius;
//cout<<"****The Circle Circumferunce is****\n"<<circumference<<"\n";
}

};

class Cylinder:public Circle_computations
{

protected:
	double height,volume,cyarea;

public:
	Cylinder(double h)
	
		//:Circle_computations(radi);
	{
		height=h;


	}

	void cy_area()
{
	cyarea=(2 * (Circle_computations::c_area()))+( c_circumferunce()* height) ;

}


void c_volume()
{
	volume = (Circle_computations::c_area())* height;


}

















};


void main()

{
double r,heigh_t;
cout<<"**Please Enter The Radius First** \n";
cin>> r;
cout<<"**Please Enter The height** \n";
cin>>heigh_t;

Circle_computations  compute(r);
Cylinder computecylider(heigh_t);
cout<<"****The  Area OF The Circle  is****\n";
compute.c_area();
cout<<"\n";
cout<<"****The Circle Circumferunce is****\n";
compute.c_circumferunce();
cout<<"\n";
cout<<"****The cylinder surface  Area   is****\n";
computecylider.cy_area();
cout<<"\n";
cout<<"****The cylinder volume   is****\n";
computecylider.c_volume();
cout<<"\n";

[keskiverto]

Error 1 error C2512: 'Circle_computations' : no appropriate default constructor available

Circle_computations has an explicit constructor Circle_computations(double)
and therefore the compiler does not generate default constructor.

You have commented out a call to constructor on line 46. Why?

Error 4 error C2296: '*' : illegal, left operand has type 'void'

void Circle_computations::c_area();

volume = (Circle_computations::c_area())* height;

c_area() is a function that returns void. Therefore, you are trying to evaluate
volume = void * height;
That does not compute.

[BotoolZyoud]

thank you i correct the error but there is rubbish values
#include<iostream>
using namespace std;

class Circle_computations
{

public:
double area,circumference,radius,pi;

public:


Circle_computations()
{
}
Circle_computations(double radi)
{
pi = 3.14;
radius=radi;


}

double c_area()
{

area = pi*radius*radius;
return area;

}

double c_circumferunce()
{

circumference =2*pi*radius;
return circumference;

}

};

class Cylinder:public Circle_computations
{

protected:
double height,volume,cyarea;

public:
Cylinder(double h)
{



height=h;


}

double cy_area()
{
cyarea=(2 * (Circle_computations::c_area()))+( c_circumferunce()* height) ;


}


double c_volume()
{
volume = (Circle_computations::c_area())* height;

return volume;

}

};


int main()

{
double r,heigh_t;
cout<<"**Please Enter The Radius First** \n";
cin>> r;
cout<<"**Please Enter The height** \n";
cin>>heigh_t;

Circle_computations compute(r);
Cylinder computecylider(heigh_t);

cout<<compute.c_area();
cout<<"\n";
cout<<"****The Circle Circumferunce is****\n";
cout<<compute.c_circumferunce();
cout<<"\n";
cout<<"****The cylinder surface Area is****\n";
cout<<computecylider.cy_area();
cout<<"\n";
cout<<"****The cylinder volume is****\n";
cout<<computecylider.c_volume();
cout<<"\n";



int g;
cin>>g;
}

[SneakySnake]

There are two errors here.

The more obvious one is that you omitted the return statement from cy_area().

The more subtle one is that Cylinder's computations depend on Circle's c_area() and c_circumference(), which in turn use Circle's radius member.
But you never initialize it when you construct Cylinder.

The best solution is to call Circle's constructor in the member initializer list.

Cylinder(double r, double h) :
    Circle_computations(r)
{
    height = h;
}