I have this programming assignment for an intro c++ class. The program is supposed to use virtual functions to input, calculate and display quantities associated with various shapes. The Shape class must contain all pure virtual functions: display, getdimensions, area, perimeter, and volume.
The program driver must allocate an array of 20 pointers to Shape then repeatedly fill the array with the objects entered.
My program is quitting when it gets to the display call. So I take this to mean that either my getDimensions or display functions are not working correctly. I've spent hours trying to sort it out and can't seem to find what exactly is wrong if anyone could point me in the right direction.
Here is my code:
#include <iostream>
#include <cmath>
using namespace std;
const double PI=3.141592654;
class Shape
{
protected:
double x, y;
public:
Shape(): x(1.0),y(1.0){}
Shape(double a, double b): x(a),y(b){}
virtual void display()=0;
virtual void getDimensions()=0;
virtual double area()=0;
virtual double perimeter()=0;
virtual double volume()=0;
};
class Rectangle: public Shape
{
public:
Rectangle():Shape(){}
Rectangle(double a, double b):Shape(a,b){}
void display();
void getDimensions()
{
cout<<"Input for Rectangle - "
<<"enter length and width: ";
cin>>x>>y;
}
double area()
{return x*y;}
double perimeter()
{return (2*x)+(2*y);}
double volume()
{return 0;}
};
class Circle: public Shape
{
private:
double radius;
public:
Circle(): radius(1.0){}
Circle(double r): radius(r){}
void display();
void getDimensions()
{
cout<<"Input for Circle - enter radius: ";
cin>>radius;
}
double area()
{return PI*radius*radius;}
double perimeter()
{return 2*PI*radius;}
double volume()
{return 0;}
};
class Triangle: public Shape
{
private:
double z;
public:
Triangle():z(1.0), Shape(){}
Triangle(double f, double g, double w):z(w), Shape(f,g){}
void display();
void getDimensions()
{
cout<<"Input for Triangle - "
<<"enter side 1, side 2, side 3: ";
cin>>x>>y>>z;
}
double area()
{
double half, underroot;
half = perimeter()/2;
underroot = half*(half-x)*(half-y)*(half-z);
return sqrt(underroot);
}
double perimeter()
{return x+y+z;}
double volume()
{return 0;}
};
class Box: public Shape
{
private:
double p;
public:
Box():p(1.0), Shape(){}
Box(double a, double b, double c): Shape(a,b), p(c){}
void display();
void getDimensions()
{
cout<<"Input for Box - "
<<"enter length, width, and height: ";
cin>>x>>y>>p;
}
double area()
{return (2*x*y)+(2*x*p)+(2*y*p);}
double perimeter()
{return 0;}
double volume()
{return x*y*p;}
};
class Can: public Shape
{
public:
Can():Shape(){}
Can(double r, double h):Shape(r,h){}
void display();
void getDimensions()
{
cout<<"Input for Can - "
<<"enter radius and height: ";
cin>>x>>y;
}
double area()
{
double base;
base = PI*x*x;
return (2*PI*x*y)+(2*PI*x*x);
}
double perimeter()
{return 0;}
double volume()
{return PI*x*x*y;}
};
class Cone: public Shape
{
public:
Cone():Shape(){}
Cone(double r, double h):Shape(r, h){}
void display();
void getDimensions()
{
cout<<"Input for Cone - "
<<"enter radius and height: ";
cin>>x>>y;
}
double area()
{
double underroot;
underroot = sqrt((x*x)+(y*y));
return (PI*x*x)+(PI*x*underroot);
}
double perimeter()
{return 0;}
double volume()
{return (1/3)*PI*x*x*y;}
};
class Ball: public Shape
{
private:
double radius;
public:
Ball():radius(1.0){}
Ball(double r):radius(r){}
void display();
void getDimensions()
{
cout<<"Input for Ball - "
<<"enter radius: ";
cin>>radius;
}
double area()
{return 4*PI*radius*radius;}
double perimeter()
{return 0;}
double volume()
{return (4/3)*PI*radius*radius*radius;}
};
int main()
{
int cnt=0, cnt2=0, choice;
char yorn;
Shape *sPtr[20];
while(cnt<20)
{
cnt++;
cnt2++;
cout<<"\nIt is time to enter your shape selection"
<<" and dimensions.\n"
<<"Enter the number of the shape type: \n"
<<"\t1 - Rectangle\n"
<<"\t2 - Circle\n"
<<"\t3 - Triangle\n"
<<"\t4 - Box\n"
<<"\t5 - Can\n"
<<"\t6 - Cone\n"
<<"\t7 - Ball\n"
<<"=> ";
cin>>choice;
while (choice<1||choice>7)
{
cout<<"Invalid selection. Re-enter: \n"
<<"=> ";
cin>>choice;
}
switch (choice)
{
case 1:
{
sPtr[cnt]=new Rectangle;
sPtr[cnt]->getDimensions();
break;
}
case 2:
{
sPtr[cnt]=new Circle;
sPtr[cnt]->getDimensions();
break;
}
case 3:
{
sPtr[cnt] = new Triangle;
sPtr[cnt]->getDimensions();
break;
}
case 4:
{
sPtr[cnt] = new Box;
sPtr[cnt]->getDimensions();
break;
}
case 5:
{
sPtr[cnt] = new Can;
sPtr[cnt]->getDimensions();
break;
}
case 6:
{
sPtr[cnt] = new Cone;
sPtr[cnt]->getDimensions();
break;
}
case 7:
{
sPtr[cnt] = new Ball;
sPtr[cnt]->getDimensions();
break;
}
}
cout<<"\nSelect another shape? (y or n): ";
cin>>yorn;
if(yorn=='n'||yorn=='N')
cnt=20;
}
for(int i=0; i<cnt2; i++)
{
sPtr[i]->display();
}
return 0;
}
void Rectangle::display()
{
cout<<"\nRectangle: "
<<"\nDimensions: "
<<"Length: "<<x<<"\nWidth: "<<y
<<"\nArea: "<<area()
<<"\nPerimeter: "<<perimeter();
}
void Circle::display()
{
cout<<"\nCircle: "
<<"\nDimensions: "
<<"\nRadius: "<<radius
<<"\nArea: "<<area()
<<"\nPerimeter: "<<perimeter();
}
void Triangle::display()
{
cout<<"\nTriangle: "
<<"\nDimensions: "
<<"\nSide 1: "<<x
<<"\nSide 2: "<<y
<<"\nSide 3: "<<z
<<"\nArea: "<<area()
<<"\nPerimeter: "<<perimeter();
}
void Box::display()
{
cout<<"\nBox: "
<<"\nDimensions: "
<<"\nLength: "<<x
<<"\nWidth: "<<y
<<"\nHeight: "<<p
<<"\nSurface area: "<<area()
<<"\nVolume: "<<volume();
}
void Can::display()
{
cout<<"\nBox: "
<<"\nDimensions: "
<<"\nRadius: "<<x
<<"\nHeight: "<<y
<<"\nSurface area: "<<area()
<<"\nVolume: "<<volume();
}
void Cone::display()
{
cout<<"\nCone: "
<<"\nDimensions: "
<<"\nRadius: "<<x
<<"\nHeight: "<<y
<<"\nSurface area: "<<area()
<<"\nVolume: "<<volume();
}
void Ball::display()
{
cout<<"\nBall: "
<<"\nDimensions: "
<<"\nRadius: "<<radius
<<"\nSurface area: "<<area()
<<"\nVolume: "<<volume();
}
You're displaying starting from 0:
for(int i=0; i<cnt2; i++)
{
sPtr[i]->display();
}
But you're adding to sPtr starting at 1:
int cnt=0;
while(cnt<20)
{
cnt++;
...
sPtr[cnt] = new ...;
}
These kinds of errors are a great reason to prefer to use std::vector<Shape*> to raw arrays and counters. Then you could just write the following, which is less error-prone:
std::vector<Shape*> shapes;
while (shapes.size() < 20) {
...
shapes.push_back(new Rectangle);
...
}
for (size_t i = 0; i < shapes.size(); ++i) {
shapes[i]->display();
}
Or really, in C++11, this should be a vector<unique_ptr<Shape>>.