Assistance with classes...

Bravebird · #1 25-Apr-2005, 18:05

Hello all...

I was given the following project to complete:

Write the declarations and definitions for the geometric classes defined in Figure 12-21. Use the following hints:
a.Define Shape, Two-Dimensional and Three-Dimensional as abstract classes.
b.Define PI as static class member in the Shape class.
c.Define area calculation and print functions as pure virtual functions in the Shape class.
d.Use public inheritance.
e.Define all data or member functions common to two-dimensional shapes in the Two-dimensional class. Do the same for all common data or member functions for the three-dimensional shape.
Figure 12-21
Shape:
-Two Dimensional
Triangle
Rectangle
Circle
-Three Dimensional
Cone
Cube
Sphere

I have a clear understanding of what to do with the two dimensional class...its the three dimensional class I'm having trouble with. If there is anyone that can provide me with some direction I would really appreciate.

Thanks!

rdrast · #2 25-Apr-2005, 19:23

What's the difficulty?

Two dimensional is area, square inches, square feet, square meters...
Three dimensional is volume. Cubic inches, cubic centimeters, etc.

Maybe your first step would be to write out eh formulas and characteristics of each shape?

(example)
Triangle:
Sides - 3
Enclosed angle - 180 degrees
Primary measurements: Base * height
Area calculation: 1/2 * base * height

Bravebird · #3 25-Apr-2005, 19:47

mhmm...that makes alot more sense...create an algorithm.

Thanks!

Bravebird · #4 27-Apr-2005, 11:24

Ok, I am now running into three errors now that I have compiled the program...I don't know what they mean though. Heres the program:

CPP / C++ / C Code:

//___________

#include<iostream>
#include<math.h>
using namespace std;
class shape
{
protected:
	double area;
	virtual void calcArea() = 0;
	virtual void print() = 0;
public:
	static float PI;
};


class two_dim : public shape
{
protected:
	double perimeter;
	virtual void calcPeri() = 0;
};


class Rectangle : public two_dim
{
private:
	double sideA;
	double sideB;
public:
	Rectangle(double sideAIn, double sideBIn);
	virtual void calcPeri();
	virtual void print();
	virtual void calcArea();
};


class three_dim : public shape
{
protected:
	double volume;
	virtual void calcVol() = 0;
};


class Cube : public three_dim
{
private:
	double sideLen;
	double surfaceArea;
	int a;
public:
	Cube(double sideIn, int a);
	virtual void calcVol();
	virtual void print();
	virtual void calcsurfaceArea();
};

Rectangle :: Rectangle (double sideAIn, double sideBIn)
{
	sideA = sideAIn;
	sideB = sideBIn;
	calcPeri ();
	calcArea ();
}

void Rectangle::calcPeri()
{
	perimeter = 2 * + (sideA + sideB);
	return;
}

void Rectangle::calcArea()
{
	area = sideA * sideB;
	return;
}

void Rectangle :: print ()
{
	cout << "\nA rectangle with sides of " << sideA << ", and " << sideB << " will have:\n\nPerimeter = " << perimeter << "\nArea = " << area << "\n\n";
	return;
}

Cube :: Cube (double sideIn, int a)
{
	sideLen = sideIn;
}

void Cube::calcVol()
{
	volume = pow(sideLen,3); 
	return;
}

void Cube::calcsurfaceArea ()
{
	surfaceArea = 6 * a ^ 2;
	return;
}

void Cube :: print ()
{
	cout << "\n\nA cube with sides equal to " << sideLen << " will have:\n\nVolume = " 
		 << volume << "\n\n";
	cout << "\n\nThe surface area is equal to: "<< surfaceArea << "\n\n";
	return;
}

int main()
{
	Rectangle rec(4,6);
	rec.calcPeri();
	rec.calcArea();
	rec.print ();
	
	Cube cub(3,7);
	cub.calcVol();
	cub.calCsurfaceArea;
	cub.print();

	return 0;
}

I believe that it has something to do with the integer "a" that I implemented...but I don't know how do go about correcting it.

Can anyone help?

WaltP · #5 27-Apr-2005, 12:33

Read the sticky. Read the sticky. Read the sticky.

It's not hard to find. It's at the top of the forum with the useful title
Guidelines for posting requests for help

Bravebird · #6 27-Apr-2005, 13:28

Quote:

Originally Posted by WaltP

Read the sticky. Read the sticky. Read the sticky.

It's not hard to find. It's at the top of the forum with the useful title
Guidelines for posting requests for help

CPP / C++ / C Code:

//___________

#include<iostream>
#include<math.h>
using namespace std;
class shape
{
protected:
double area;
virtual void calcArea() = 0;
virtual void print() = 0;
public:
static float PI;
};


class two_dim : public shape
{
protected:
double perimeter;
virtual void calcPeri() = 0;
};


class Rectangle : public two_dim
{
private:
double sideA;
double sideB;
public:
Rectangle(double sideAIn, double sideBIn);
virtual void calcPeri();
virtual void print();
virtual void calcArea();
};


class three_dim : public shape
{
protected:
double volume;
virtual void calcVol() = 0;
};


class Cube : public three_dim
{
private:
double sideLen;
double surfaceArea;
int a;
public:
Cube(double sideIn, int a);
virtual void calcVol();
virtual void print();
virtual void calcsurfaceArea();
};

Rectangle :: Rectangle (double sideAIn, double sideBIn)
{
sideA = sideAIn;
sideB = sideBIn;
calcPeri ();
calcArea ();
}

void Rectangle::calcPeri()
{
perimeter = 2 * + (sideA + sideB);
return;
}

void Rectangle::calcArea()
{
area = sideA * sideB;
return;
}

void Rectangle :: print ()
{
cout << "\nA rectangle with sides of " << sideA << ", and " << sideB << " will have:\n\nPerimeter = " << perimeter << "\nArea = " << area << "\n\n";
return;
}

Cube :: Cube (double sideIn, int a)
{
sideLen = sideIn;
}

void Cube::calcVol()
{
volume = pow(sideLen,3); 
return;
}

void Cube::calcsurfaceArea ()
{
surfaceArea = 6 * a ^ 2;
return;
}

void Cube :: print ()
{
cout << "\n\nA cube with sides equal to " << sideLen << " will have:\n\nVolume = " 
<< volume << "\n\n";
cout << "\n\nThe surface area is equal to: "<< surfaceArea << "\n\n";
return;
}

int main()
{
Rectangle rec(4,6);
rec.calcPeri();
rec.calcArea();
rec.print ();

Cube cub(3,7);
cub.calcVol();
cub.calcsurfaceArea;
cub.print();

return 0;
}

Dave Sinkula · #7 27-Apr-2005, 13:56

This is not my strong suit, but I'll give it a whirl.

http://www.parashift.com/c++-faq-lit....html#faq-22.4

Your Cube is a public three_dim, which has a pure virtual function calcVol; so Cube must define one. You do that, okay.

Your three_dim is a public shape, which has pure virtual functions calcArea and print; so you must define them for Cube as well. You don't: problem.

So if you add these to Cube:

CPP / C++ / C Code:

virtual void print();
virtual void calcArea();

And change this...

CPP / C++ / C Code:

void Cube::calcsurfaceArea () // note name
{
surfaceArea = 6 * a ^ 2; // I doubt you are trying to XOR a with 2
return;
}

...to this

CPP / C++ / C Code:

void Cube::calcArea () // see the name
{
   surfaceArea = 6 * pow(sideLen, 2); // you want sideLen squared, right?
   return;
}

And then instead of attempting to call the function like this...

CPP / C++ / C Code:

cub.calcsurfaceArea;

...you call the function like this

CPP / C++ / C Code:

cub.calcArea();

Then I think some of the compile issues are taken care of.

Bravebird · #8 27-Apr-2005, 14:17

Thank you soo much! That helped alot...as well as the link.

I appreciate it!

Quote:

Originally Posted by Dave Sinkula

This is not my strong suit, but I'll give it a whirl.

http://www.parashift.com/c++-faq-lite/abcs.html#faq-22.4

Your Cube is a public three_dim, which has a pure virtual function calcVol; so Cube must define one. You do that, okay.

Your three_dim is a public shape, which has pure virtual functions calcArea and print; so you must define them for Cube as well. You don't: problem.

So if you add these to Cube:

CPP / C++ / C Code:

virtual void print();
virtual void calcArea();

And change this...

CPP / C++ / C Code:

void Cube::calcsurfaceArea () // note name
{
surfaceArea = 6 * a ^ 2; // I doubt you are trying to XOR a with 2
return;
}

...to this

CPP / C++ / C Code:

void Cube::calcArea () // see the name
{
   surfaceArea = 6 * pow(sideLen, 2); // you want sideLen squared, right?
   return;
}

And then instead of attempting to call the function like this...

CPP / C++ / C Code:

cub.calcsurfaceArea;

...you call the function like this

CPP / C++ / C Code:

cub.calcArea();

Then I think some of the compile issues are taken care of.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Rate This Thread
Rate This Thread:

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Help using const arrays in c++ classes	FlipNode	C++ Forum	5	31-Mar-2005 02:16
bug w/ templated classes	f15e	MS Visual C++ / MFC Forum	4	07-Mar-2005 00:56
Fairly simple classes help please	sammacs	C++ Forum	0	30-Nov-2004 10:58
ClassView not showing my classes (VC++, namespace, headers) ?!?!?	djovanov	C++ Forum	1	13-Jan-2004 05:54
using windows WMI and CMI classes in Dev-c++	Dawis	C++ Forum	0	26-Oct-2003 05:18

Assistance with classes...

Errors...

I apologize...

Thanks!