Functions and Classes - Where did I go wrong?

redmage · #1 10-Apr-2005, 12:55

I am doing an online very beginner programming class. I know I'm on the right track, but the book I have is the wrong one and it's no help. This is the assignment:

Create a class Rectangle. The class has private attributes length and width, each of which defaults to 1. It has member functions that calculate the perimeter and the area of the rectangle. It has set and get functions for both length and width.

The set functions (i.e. setLength() and setWidth()) should verify that length and width are larger than 0.0 and less than 20.0. If the parameter does not satisfy, use default value = 1.0

The get functions (i.e. getLength() and getWidth() ) should return the value of the attributes.

The constructor should use the set functions to initialize the attributes.

The following is main function you should use. The main idea is that, given three rectangles a, b and c, output their lengths, widths, perimeters and areas. Include header files when necessary.

I thought I knew how to do it, but for some reason I'm stumbling on... something. I just don't know what's going wrong, and I know it must be really basic. I'm pretty sure I'm missing something, but I'm not sure what to look up in a tutorial to fix what's wrong, you know?

CPP / C++ / C Code:

//this is my coding

#include <iostream>


using namespace std;

class rectangle {
  private:
	int width, height;
  public:
    rectangle ();
    rectangle (int,int);
    int area (void) {return (x*y);
	int perimeter (void) {return (x*2 + y*2);}
	
};

rectangle::rectangle () //a tutorial online said that's how you set defaults
{
  x = 1;
  y = 1;
}

rectangle::rectangle (int x, int y) //derived from notes
{
  width = x;
  height = y;
}




//this is what was given
int main()
{
	Rectangle a, b(4.0,5.0), c(67.0, 888.0);
	cout<< setiosflags(ios::fixed | ios::showpoint);
	cout<<setprecision(1);

	cout<<"a: length = " << a.getLength() << "; width = " << a.getWidth()
                                            << "area = " << a.area() <<'\n';

	cout<< "b: length = " << b.getLength() << "; width = " << b.getWidth() 
                                                     << "; perimeter = " << b.perimeter()
                                                     << "; area = " << b.area() << '\n';

	cout << "c: length = " << c.getLenght() << "; width = " << c.getWidth() 
                                                      << "; perimeter =" << c.perimeter() 
                                                      << "; area = " << c.area() << endl;

	return 0;
}

//my coding again



int setWidth() //because it is based on a, b, and c, it is blank, right?
{
    if ((x < 0.0) || (x > 20.0)) 
	{
		x = 1.0;
	}
	Return x;
}
//have to use X and Y because Width and Height are private, right?
int setHeight() 
{
    if ((y < 0.0) || (y > 20.0))
    {
        y = 1.0;
    }
  return y;
}

When I compile, I get three errors:
"error C2535: '__thiscall rectangle::rectangle(void)' : member function already defined or declared"
(that one I get twice)

"fatal error C1004: unexpected end of file found
Error executing cl.exe."

This is of course due tonight (asking online was my last resort after trying to make it work on my own) and if someone can just tell me where I'm going wrong and how I should be tackling it instead I'd appriciate it.

kai85 · #2 10-Apr-2005, 14:56

well , first im a newbie myself ... and ive only just started oop, but i do see some major erors in youre code;
first u should know that c++ is case sensitive, if u have a class called rectangle, then when ur creating objects u should use rectangle as the variable type not Rectangle...check ur spelling Return!(return) lenght!(length)....
2. i think u get unexpected end of .... because uve missed a brace here:

CPP / C++ / C Code:

int area (void) {return (x*y);

3.i suggest u declare ur constructers inside ur class decleration ...its better if made they're into inline functions... u won't get the errors u mentioned!
4. I think what u mean here is:

CPP / C++ / C Code:

rectangle::rectangle () //a tutorial online said that's how you set defaults
{
  x = 1;
  y = 1;
}

CPP / C++ / C Code:

{
  height = 1;
  width = 1;
}

anyway Hope i helped... (even though im not so sure i did)

redmage · #3 10-Apr-2005, 17:09

Ok, this is where I'm at now:

CPP / C++ / C Code:

//this is my coding

#include <iostream>
#include <iomanip>

using namespace std;

class rectangle {
    private:
    double Width, Lenght;  
  public:
	  rectangle () {Width = 1.0, Lenght = 1.0;}; 
    rectangle (double,double);
    double area (void) const {return (Width*Lenght);}
    double perimeter (void) const {return (Lenght*2 + Width*2);}
    void setWidth(double x);
    void setLenght(double y);
    double getWidth() const;
    double getLenght() const;

	
};

void rectangle::setWidth(double x;)
{
    if ((x < 0.0;) || (x > 20.0;))
	{
		Width = 1.0;
	}
	Width = x;


}

void rectangle::setLenght(double y;)
{
    if ((y < 0.0;) || (y > 20.0;))
	{
		Lenght = 1.0;
	}
Lenght = y;

}

int rectangle::getWidth()
{
   return Width;

}

int rectangle::getLenght()
{
   return Lenght;


}


//this is what was given
int main()
{
	rectangle a, b(4.0,5.0), c(67.0, 888.0);
	cout<< setiosflags(ios::fixed | ios::showpoint);
	cout<<setprecision(1);

	cout<<"a: length = " << a.getLenght() << "; width = " << a.getWidth()
                                            << "area = " << a.area() <<'\n';

	cout<< "b: length = " << b.getLenght() << "; width = " << b.getWidth() 
                                                     << "; perimeter = " << b.perimeter()
                                                     << "; area = " << b.area() << '\n';

	cout << "c: length = " << c.getLenght() << "; width = " << c.getWidth() 
                                                      << "; perimeter =" << c.perimeter() 
                                                      << "; area = " << c.area() << endl;

	return 0;
}

ERRORS

Code:

C:\Documents and Settings\Chris\Cpp1.cpp(24) : error C2143: syntax error : missing ')' before ';'
C:\Documents and Settings\Chris\Cpp1.cpp(24) : error C2059: syntax error : ')'
C:\Documents and Settings\Chris\Cpp1.cpp(25) : error C2447: missing function header (old-style formal list?)
C:\Documents and Settings\Chris\Cpp1.cpp(35) : error C2143: syntax error : missing ')' before ';'
C:\Documents and Settings\Chris\Cpp1.cpp(35) : error C2059: syntax error : ')'
C:\Documents and Settings\Chris\Cpp1.cpp(36) : error C2447: missing function header (old-style formal list?)
C:\Documents and Settings\Chris\Cpp1.cpp(46) : error C2511: 'getWidth' : overloaded member function 'int (void)' not found in 'rectangle'
        C:\Documents and Settings\Chris\Cpp1.cpp(8) : see declaration of 'rectangle'
C:\Documents and Settings\Chris\Cpp1.cpp(57) : error C2511: 'getLenght' : overloaded member function 'int (void)' not found in 'rectangle'
        C:\Documents and Settings\Chris\Cpp1.cpp(8) : see declaration of 'rectangle'

LuciWiz · #4 10-Apr-2005, 17:39

You have lots of misplaced semicolons in your code:

CPP / C++ / C Code:

void rectangle::setWidth(double x;) // 1
{
    if ((x < 0.0;) || (x > 20.0;)) // 2, 3

And more. Please remove them (what were you trying to do?)

Also, you defined two of your member functions to return double, but then you changed them to int. The compiler won't like it

CPP / C++ / C Code:

double getWidth() const;

//...

//      And later
int rectangle::getWidth()

It should be double AND const. You need to specify this too.

CPP / C++ / C Code:

double rectangle::getWidth() const
{
	return Width;
}

But now you'll have a problem with the fact that the compiler can't find an implementation for your overloaded constructor. You need to build one:

CPP / C++ / C Code:

rectangle::rectangle (double width, double length)
{
	Width = width;
	Length = length;
}

//or
rectangle::rectangle (double width, double length) : Width(width), Length(length)
{
	// other stuff
}

Or you could do this too in the definition of the class. However, I find this approach cumbersome, since I think this led you to forgetting about it in the first place. Plus it makes your class definition less readable.
Other people feel different about this, so you can go with whatever you choose...

Best regards,
Lucian

redmage · #5 10-Apr-2005, 18:07

Ok, I've gotten the coding itself compile-able, but when I run it I get insanely wrong answers that I'm having trouble tracing:

"a: length = -858993460; width = -858993460area = 1
b: length = 5; width = 4; perimeter = 858993456; area = 687194768
c: length = 888; width = 67; perimeter =858993456; area = 687194768
Press any key to continue"

This is the calculating part:

CPP / C++ / C Code:

#include "Rectangle.h"

Rectangle::Rectangle()
{
	x = 1;
	y = 1;
}


Rectangle::Rectangle(int x, int y)
{
	width = x;
	length = y;
}

int Rectangle::getWidth() 
{ 
	return width; 
}

int Rectangle::getLength() 
{ 
	return length; 
}

int Rectangle::setWidth(int x)
{
	if ((x < 0) || (x > 20)) 
		x = 1;

	return getWidth();
}

int Rectangle::setLength(int y) 
{
    if ((y < 0) || (y > 20))
		y = 1;
	
	return getLength();
}

Header

CPP / C++ / C Code:

class Rectangle 
{
private:
	int x, y;
	int width, length;

public:
	Rectangle ();
    Rectangle (int, int);
	
	int setWidth(int x);
	int setLength(int y);
	int getWidth();
	int getLength();
	
	int area (void) { return (x * y); }
	int perimeter (void) { return (x * 2 + y * 2); }


};

And the main's the same as the given in the original code.

WaltP · #6 10-Apr-2005, 19:31

It seems to me that setWidth() should actually set the width. Otherwise what is it for? In your code:

CPP / C++ / C Code:

int Rectangle::setWidth(int x)
{
  if ((x < 0) || (x > 20)) 
    x = 1;

  return getWidth();
}

checks the value of the parameter x then returns the width from your rectangle class. the input parameter is never used. You might want to consider testing x as you do and setting width to either x or 1 as appropriate.

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