Inheritance with pointers:Overloading?

[Katie]

my one base class is a linklist class.now i'd like to inherit it by
another class.The problem is that when i use the derived class i can't
access the base class's pointers.classi c type mismatch.how do i link
the derived class if i can't compare the derived class's pointers to
the linklist class's pointers?
do i do it with overloading?i tried that,but could get it to work.my
handbooks (all 4 of them) has no example on how to do overloading.can
someone help?e-mail if you want to.please, i'm on a deadline!!!

[Buster]

Re: Inheritance with pointers:Overlo ading?

Katie wrote:
[color=blue]
> my one base class is a linklist class.[/color]

You have defined a class called "linklist". OK.
[color=blue]
> now i'd like to inherit it by
> another class.[/color]

You want to define another class, derived from "linklist". OK.
[color=blue]
> The problem is that when i use the derived class i can't
> access the base class's pointers.[/color]

Now you've lost me. Why not? What pointers? How do you "use"
the derived class?
[color=blue]
> classic type mismatch.[/color]

What?
[color=blue]
> how do i link the derived class if i can't compare the derived
> class's pointers to the linklist class's pointers?[/color]

What does it mean to "link" a class?

You _can_ compare a base class pointer and a derived class pointer
for equality. Did you use two equals signs, like `=='?
[color=blue]
> do i do it with overloading?[/color]

I shouldn't think so. Without knowing more about the
problem it's impossible to say for sure.
[color=blue]
> i tried that,but could get it to work.[/color]

Right.
[color=blue]
> my handbooks (all 4 of them) has no example on how to do overloading.[/color]

Borrow or buy a better book. There are reviews on the ACCU site.
More recent reviews are more useful because the way people use C++
has evolved. "The C++ Programming Language", 3rd/Special edition,
by Bjarne Stroustrup, covers the whole language nicely. I don't know
that it's very suitable for a beginner.
[color=blue]
> can someone help?[/color]

I tried, really. I don't understand what you are trying to do.
Can you show us the program you are trying to compile?
[color=blue]
> e-mail if you want to.[/color]

Post here, read here.
[color=blue]
> please, i'm on a deadline!!![/color]

Good luck with that.

--
Regards,
Buster.

[Buster]

Re: Inheritance with pointers:Overlo ading?

Katie wrote:
[color=blue]
> my one base class is a linklist class.[/color]

You have defined a class called "linklist". OK.
[color=blue]
> now i'd like to inherit it by
> another class.[/color]

You want to define another class, derived from "linklist". OK.
[color=blue]
> The problem is that when i use the derived class i can't
> access the base class's pointers.[/color]

Now you've lost me. Why not? What pointers? How do you "use"
the derived class?
[color=blue]
> classic type mismatch.[/color]

What?
[color=blue]
> how do i link the derived class if i can't compare the derived
> class's pointers to the linklist class's pointers?[/color]

What does it mean to "link" a class?

You _can_ compare a base class pointer and a derived class pointer
for equality. Did you use two equals signs, like `=='?
[color=blue]
> do i do it with overloading?[/color]

I shouldn't think so. Without knowing more about the
problem it's impossible to say for sure.
[color=blue]
> i tried that,but could get it to work.[/color]

Right.
[color=blue]
> my handbooks (all 4 of them) has no example on how to do overloading.[/color]

Borrow or buy a better book. There are reviews on the ACCU site.
More recent reviews are more useful because the way people use C++
has evolved. "The C++ Programming Language", 3rd/Special edition,
by Bjarne Stroustrup, covers the whole language nicely. I don't know
that it's very suitable for a beginner.
[color=blue]
> can someone help?[/color]

I tried, really. I don't understand what you are trying to do.
Can you show us the program you are trying to compile?
[color=blue]
> e-mail if you want to.[/color]

Post here, read here.
[color=blue]
> please, i'm on a deadline!!![/color]

Good luck with that.

--
Regards,
Buster.

[Katie]

Re: Inheritance with pointers:Overlo ading?

Buster <noone@nowhere. com> wrote in message news:<c56q76$uq 0$1@news6.svr.p ol.co.uk>...[color=blue]
> Katie wrote:
>[color=green]
> > my one base class is a linklist class.[/color]
>
> You have defined a class called "linklist". OK.
>[color=green]
> > now i'd like to inherit it by
> > another class.[/color]
>
> You want to define another class, derived from "linklist". OK.
>[color=green]
> > The problem is that when i use the derived class i can't
> > access the base class's pointers.[/color]
>
> Now you've lost me. Why not? What pointers? How do you "use"
> the derived class?
>[color=green]
> > classic type mismatch.[/color]
>
> What?
>[color=green]
> > how do i link the derived class if i can't compare the derived
> > class's pointers to the linklist class's pointers?[/color]
>
> What does it mean to "link" a class?
>
> You _can_ compare a base class pointer and a derived class pointer
> for equality. Did you use two equals signs, like `=='?
>[color=green]
> > do i do it with overloading?[/color]
>
> I shouldn't think so. Without knowing more about the
> problem it's impossible to say for sure.
>[color=green]
> > i tried that,but could get it to work.[/color]
>
> Right.
>[color=green]
> > my handbooks (all 4 of them) has no example on how to do overloading.[/color]
>
> Borrow or buy a better book. There are reviews on the ACCU site.
> More recent reviews are more useful because the way people use C++
> has evolved. "The C++ Programming Language", 3rd/Special edition,
> by Bjarne Stroustrup, covers the whole language nicely. I don't know
> that it's very suitable for a beginner.
>[color=green]
> > can someone help?[/color]
>
> I tried, really. I don't understand what you are trying to do.
> Can you show us the program you are trying to compile?
>[color=green]
> > e-mail if you want to.[/color]
>
> Post here, read here.
>[color=green]
> > please, i'm on a deadline!!![/color]
>
> Good luck with that.[/color]

here follows the whole program
any help would be appreciated

#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>
#include <stdio.h>
#include <iostream.h>
#include <dos.h>

//class definition of link list
class LLClass
{
protected:
class LLClass *next; //pointer to next position
class LLClass *prev; //pointer to previous position



public:
LLClass();
~LLClass();
void setnext(class LLClass *temp);
void setprev(class LLClass *temp);

virtual class LLClass *getnext();
virtual class LLClass *getprev();

};
LLClass::LLClas s()
{};

LLClass::~LLCla ss()
{}

void LLClass::setnex t(class LLClass *temp)
{
next=temp;
}//setnext

void LLClass::setpre v(class LLClass *temp)
{
prev=temp;
}//setprev

class LLClass *LLClass::getne xt()
{
return next;
}//getnext

class LLClass *LLClass::getpr ev()
{
return prev;
}//getprev

//class definition for class point
class Point
{
private:
int x,y; //top left corner
int color; //color of the box
int direction; //direction the rectangle is going


public:
Point();
~Point();

int xx,yy; //public coordinates
int chcolor; //change in the color
int dir; //the direction of the box

void setvalues(int xx, int yy); //get values for x,y
void setcolor(int chcolor); //change the color
void setdir(int dir); //change the direction

int getx();
int gety();
int getcolor();
int getdir();

int inccolor();
int deccolor();
int incx();
int decx();
int incy();
int decy();
};
Point::Point()
{
x=y=0; //default box at 0
direction=0; //default direction at 0
color=2; //default color green
}//cnstrctr
Point::~Point()
{}

void Point::setvalue s(int xx, int yy)
{
x=xx;
y=yy;
}//setvalues

void Point::setcolor (int chcolor)
{
color=chcolor;
}//setcolor

void Point::setdir(i nt dir)
{
direction=dir;
}//setdir

int Point::getx()
{
return x;
}//getx

int Point::gety()
{
return y;
}//gety

int Point::getcolor ()
{
return color;
}//getcolor

int Point::getdir()
{
return direction;
}//getdir

int Point::inccolor ()
{
color++;
return color;
}//inccolor

int Point::deccolor ()
{
color--;
return color;
}//deccolor

int Point::incy()
{
y++;
return y;
}//incy

int Point::decy()
{
y--;
return y;
}//decy

int Point::incx()
{
x++;
return x;
}//incx

int Point::decx()
{
x--;
return x;
}//decx

//class definition of rectangle
class Rectangle:publi c LLClass,public Point
{
private:
int b,t;


public:
Rectangle(); //constructor
~Rectangle(); //destructor
class Rectangle *newptr,*first, *last,*curr;//pointers

//functions in class
void setrnext(class LLClass *temp);
class LLClass *convnext(class LLClass *temp);
class Rectangle *getrnext(); //next pointer


class LLClass *getnext(); //next pointer
class LLClass *getprev(); //prev pointer
};
Rectangle::Rect angle()
{}//cnstrctr

Rectangle::~Rec tangle()
{}

class LLClass *Rectangle::get next()
{
return next;
}//getnext

class LLClass *Rectangle::get prev()
{
return prev;
}//getprev

int main(int argc,char *argv[])
{
class Rectangle *first,*last,*c urr, *newptr, *temp;
class LLClass *temp;
int rct,choice;


//auto detection
int gdriver = 0, gmode, errorcode;

//initialize graphics
initgraph(&gdri ver, &gmode, "c:\\tc\\bgi\\" );


//result of initialization
errorcode = graphresult();

if (errorcode != grOk)
{
printf("Graphic s error: %s\n", grapherrormsg(e rrorcode));
printf("Press any key to halt:");
getch();
exit(1);
}
//get the number of objects
rct=atoi(argv[1]);


//create first box
randomize();
first=curr=newp tr=new Rectangle;
first->setvalues(20+r and()%600,20+ra nd()%430);



for(int b=1;b<=rct-1;b++)
{
newptr=new Rectangle;
newptr->setvalues(20+r and()%600,20+ra nd()%430);


//linking
newptr->setprev(curr );
curr->setnext(newptr );
curr=newptr;
}//end of new box (fr)
newptr->setnext(first) ;
last=newptr;
first->setprev(newptr );

//draw outerbox
choice=0;
rectangle(1,1,6 30,470);


//problem starts here
//the linklist was created and data was written to it but i can't access it
//draw the small boxes
curr=first;
setcolor(15);
cout<<endl;
for (int j=1;j<=rct;j++)
{
temp=curr->getnext();
curr=curr->getnext();
cout<<newptr->getprev()<<" ";
cout<<newptr->getnext()<<end l;
}//fr

getch();
closegraph();
argc=argc;
choice=choice;
last=last;
return 0;
}
thx a lot

[Katie]

Re: Inheritance with pointers:Overlo ading?

Buster <noone@nowhere. com> wrote in message news:<c56q76$uq 0$1@news6.svr.p ol.co.uk>...[color=blue]
> Katie wrote:
>[color=green]
> > my one base class is a linklist class.[/color]
>
> You have defined a class called "linklist". OK.
>[color=green]
> > now i'd like to inherit it by
> > another class.[/color]
>
> You want to define another class, derived from "linklist". OK.
>[color=green]
> > The problem is that when i use the derived class i can't
> > access the base class's pointers.[/color]
>
> Now you've lost me. Why not? What pointers? How do you "use"
> the derived class?
>[color=green]
> > classic type mismatch.[/color]
>
> What?
>[color=green]
> > how do i link the derived class if i can't compare the derived
> > class's pointers to the linklist class's pointers?[/color]
>
> What does it mean to "link" a class?
>
> You _can_ compare a base class pointer and a derived class pointer
> for equality. Did you use two equals signs, like `=='?
>[color=green]
> > do i do it with overloading?[/color]
>
> I shouldn't think so. Without knowing more about the
> problem it's impossible to say for sure.
>[color=green]
> > i tried that,but could get it to work.[/color]
>
> Right.
>[color=green]
> > my handbooks (all 4 of them) has no example on how to do overloading.[/color]
>
> Borrow or buy a better book. There are reviews on the ACCU site.
> More recent reviews are more useful because the way people use C++
> has evolved. "The C++ Programming Language", 3rd/Special edition,
> by Bjarne Stroustrup, covers the whole language nicely. I don't know
> that it's very suitable for a beginner.
>[color=green]
> > can someone help?[/color]
>
> I tried, really. I don't understand what you are trying to do.
> Can you show us the program you are trying to compile?
>[color=green]
> > e-mail if you want to.[/color]
>
> Post here, read here.
>[color=green]
> > please, i'm on a deadline!!![/color]
>
> Good luck with that.[/color]

here follows the whole program
any help would be appreciated

#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>
#include <stdio.h>
#include <iostream.h>
#include <dos.h>

//class definition of link list
class LLClass
{
protected:
class LLClass *next; //pointer to next position
class LLClass *prev; //pointer to previous position



public:
LLClass();
~LLClass();
void setnext(class LLClass *temp);
void setprev(class LLClass *temp);

virtual class LLClass *getnext();
virtual class LLClass *getprev();

};
LLClass::LLClas s()
{};

LLClass::~LLCla ss()
{}

void LLClass::setnex t(class LLClass *temp)
{
next=temp;
}//setnext

void LLClass::setpre v(class LLClass *temp)
{
prev=temp;
}//setprev

class LLClass *LLClass::getne xt()
{
return next;
}//getnext

class LLClass *LLClass::getpr ev()
{
return prev;
}//getprev

//class definition for class point
class Point
{
private:
int x,y; //top left corner
int color; //color of the box
int direction; //direction the rectangle is going


public:
Point();
~Point();

int xx,yy; //public coordinates
int chcolor; //change in the color
int dir; //the direction of the box

void setvalues(int xx, int yy); //get values for x,y
void setcolor(int chcolor); //change the color
void setdir(int dir); //change the direction

int getx();
int gety();
int getcolor();
int getdir();

int inccolor();
int deccolor();
int incx();
int decx();
int incy();
int decy();
};
Point::Point()
{
x=y=0; //default box at 0
direction=0; //default direction at 0
color=2; //default color green
}//cnstrctr
Point::~Point()
{}

void Point::setvalue s(int xx, int yy)
{
x=xx;
y=yy;
}//setvalues

void Point::setcolor (int chcolor)
{
color=chcolor;
}//setcolor

void Point::setdir(i nt dir)
{
direction=dir;
}//setdir

int Point::getx()
{
return x;
}//getx

int Point::gety()
{
return y;
}//gety

int Point::getcolor ()
{
return color;
}//getcolor

int Point::getdir()
{
return direction;
}//getdir

int Point::inccolor ()
{
color++;
return color;
}//inccolor

int Point::deccolor ()
{
color--;
return color;
}//deccolor

int Point::incy()
{
y++;
return y;
}//incy

int Point::decy()
{
y--;
return y;
}//decy

int Point::incx()
{
x++;
return x;
}//incx

int Point::decx()
{
x--;
return x;
}//decx

//class definition of rectangle
class Rectangle:publi c LLClass,public Point
{
private:
int b,t;


public:
Rectangle(); //constructor
~Rectangle(); //destructor
class Rectangle *newptr,*first, *last,*curr;//pointers

//functions in class
void setrnext(class LLClass *temp);
class LLClass *convnext(class LLClass *temp);
class Rectangle *getrnext(); //next pointer


class LLClass *getnext(); //next pointer
class LLClass *getprev(); //prev pointer
};
Rectangle::Rect angle()
{}//cnstrctr

Rectangle::~Rec tangle()
{}

class LLClass *Rectangle::get next()
{
return next;
}//getnext

class LLClass *Rectangle::get prev()
{
return prev;
}//getprev

int main(int argc,char *argv[])
{
class Rectangle *first,*last,*c urr, *newptr, *temp;
class LLClass *temp;
int rct,choice;


//auto detection
int gdriver = 0, gmode, errorcode;

//initialize graphics
initgraph(&gdri ver, &gmode, "c:\\tc\\bgi\\" );


//result of initialization
errorcode = graphresult();

if (errorcode != grOk)
{
printf("Graphic s error: %s\n", grapherrormsg(e rrorcode));
printf("Press any key to halt:");
getch();
exit(1);
}
//get the number of objects
rct=atoi(argv[1]);


//create first box
randomize();
first=curr=newp tr=new Rectangle;
first->setvalues(20+r and()%600,20+ra nd()%430);



for(int b=1;b<=rct-1;b++)
{
newptr=new Rectangle;
newptr->setvalues(20+r and()%600,20+ra nd()%430);


//linking
newptr->setprev(curr );
curr->setnext(newptr );
curr=newptr;
}//end of new box (fr)
newptr->setnext(first) ;
last=newptr;
first->setprev(newptr );

//draw outerbox
choice=0;
rectangle(1,1,6 30,470);


//problem starts here
//the linklist was created and data was written to it but i can't access it
//draw the small boxes
curr=first;
setcolor(15);
cout<<endl;
for (int j=1;j<=rct;j++)
{
temp=curr->getnext();
curr=curr->getnext();
cout<<newptr->getprev()<<" ";
cout<<newptr->getnext()<<end l;
}//fr

getch();
closegraph();
argc=argc;
choice=choice;
last=last;
return 0;
}
thx a lot

[Buster]

Re: Inheritance with pointers:Overlo ading?

Katie wrote:
[color=blue]
> here follows the whole program
> any help would be appreciated[/color]

I suggest you test your LLClass class using a much simpler
object first, say

class simple : public LLClass
{
private:
int data;
public:
void setdata (int d) { data = d; }
int getdata () { return data; }

virtual simple * getnext () { return LLClass::getnex t (); }
virtual simple * getprev () { return LLClass::getpre v (); }
};

Note that standard C++, the topic of this newsgroup, has no facilities
for graphics or even coloured text. However, it does have linked lists
in the form of the std::list class template.

--
Regards,
Buster

[Buster]

Re: Inheritance with pointers:Overlo ading?

Katie wrote:
[color=blue]
> here follows the whole program
> any help would be appreciated[/color]

I suggest you test your LLClass class using a much simpler
object first, say

class simple : public LLClass
{
private:
int data;
public:
void setdata (int d) { data = d; }
int getdata () { return data; }

virtual simple * getnext () { return LLClass::getnex t (); }
virtual simple * getprev () { return LLClass::getpre v (); }
};

Note that standard C++, the topic of this newsgroup, has no facilities
for graphics or even coloured text. However, it does have linked lists
in the form of the std::list class template.

--
Regards,
Buster

[Katie]

Re: Inheritance with pointers:Overlo ading?

Buster <noone@nowhere. com> wrote in message news:<c599vl$7q 1$1@newsg2.svr. pol.co.uk>...[color=blue]
> I suggest you test your LLClass class using a much simpler
> object first, say
>
> Note that standard C++, the topic of this newsgroup, has no facilities
> for graphics or even coloured text. However, it does have linked lists
> in the form of the std::list class template.[/color]

thx
i'll try that
i'll let u know if it works

[Katie]

Re: Inheritance with pointers:Overlo ading?

Buster <noone@nowhere. com> wrote in message news:<c599vl$7q 1$1@newsg2.svr. pol.co.uk>...[color=blue]
> I suggest you test your LLClass class using a much simpler
> object first, say
>
> Note that standard C++, the topic of this newsgroup, has no facilities
> for graphics or even coloured text. However, it does have linked lists
> in the form of the std::list class template.[/color]

thx
i'll try that
i'll let u know if it works

[Katie]

Re: Inheritance with pointers:Overlo ading?

> i'll try that[color=blue]
> i'll let u know if it works[/color]

class simple : public LLClass
{
private:
int data;
public:
void setdata (int d) { data = d; }
int getdata () { return data; }

//first it cannot override the virtual LLClass *getnext:
//LLClass::getnex t cannot be returned(*LLCla ss !=*simple)
virtual simple * getnext () { return LLClass::getnex t (); }
virtual simple * getprev () { return LLClass::getpre v (); }
};

//The assignment tells us to create our own link list template

--
didn’t solve it, but thanks for the effort

[Buster]

Re: Inheritance with pointers:Overlo ading?

Katie wrote:[color=blue][color=green]
>>i'll try that
>>i'll let u know if it works[/color]
>
> class simple : public LLClass
> {
> private:
> int data;
> public:
> void setdata (int d) { data = d; }
> int getdata () { return data; }
>
> //first it cannot override the virtual LLClass *getnext:
> //LLClass::getnex t cannot be returned(*LLCla ss !=*simple)[/color]

You're right, of course. Sorry about that.
[color=blue]
> virtual simple * getnext () { return LLClass::getnex t (); }
> virtual simple * getprev () { return LLClass::getpre v (); }
> };
>
> //The assignment tells us to create our own link list template[/color]

Shame. Have you looked inside the "list" header for inspiration?
There are also many, many books which provide code for linked lists.
[color=blue]
> didn’t solve it, but thanks for the effort[/color]

--
Regards,
Buster.