Simple link list problem

karlan · 01-16-2004, 06:48 PM

can anyone look over this really quick and tell me some mistakes i made

Code:

#include <iostream>
using namespace std;
class windowLnkList{
    public:
	windowLnkList(windowLnkList *whereToPush = 0){
		////////////////
		///////Note: that above means the class after(Pnext)
		//////	     and below means the class before(Pprev)
		////////////////
		//This is where a chain link is inserted

		//(1)This is where we add references to the above/below class to this one
		Pprev = (whereToPush != 0) ? (whereToPush)               : (0);//Link to "object below's" location, if exists
		Pnext = (whereToPush != 0) ? (whereToPush->Pnext)        : (0);//Link to "object above's" location, if exists

		//(2)This is where we add references to this class to the above/below classes
		        (Pnext != 0)       ? (Pnext->Pprev = this)       : (0);//link object above, if app, to this location
			(whereToPush != 0) ? (whereToPush->Pnext = this) : (0);//link object below, if app, to this location
		}
	~windowLnkList(){
		if(Pprev != 0)//if this isn't the first item in the list
			Pprev->Pnext = Pnext;
		if(Pnext != 0)//if this isn't the last item in the list
			Pnext->Pprev = Pprev;
		}
	void display(){
		cout << "Pnext: " << &Pnext << endl;
		cout << "this: " << this << endl;
		cout << "Pprev: " << &Pprev << endl << endl;
		if(Pnext != 0){
			Pnext->display();}
		}
	windowLnkList *Pprev;
	windowLnkList *Pnext;
};
int main(int argc, char *argv){
windowLnkList class1;
//class1.display();
windowLnkList class2(class1);
//class2.display();
windowLnkList class3(class1);
class1.display();
}

macro-linux · 01-16-2004, 07:21 PM

I am in the win,so can't compile it,
but in the main function, there must be a return type,
the other I an't help you!

Hko · 01-17-2004, 08:33 AM

Isn't this:

Code:

Pprev = (whereToPush != 0) ? (whereToPush) : (0);
Pnext = (whereToPush != 0) ? (whereToPush->Pnext) : (0);

..the same as:

Code:

Pprev = whereToPush;
Pnext = whereToPush->Pnext;

And isn't this:

Code:

(Pnext != 0) ? (Pnext->Pprev = this) : (0);

... a confusing way of saying:

Code:

if (Pnext != NULL) {
        Pnext->Pprev = this;
}

spectrumver1 · 01-22-2004, 11:41 AM

yeah, but I think the (0) should be changed to NULL to prevent any value from being stored there, and I personally like the ( ) ? : way of making if statements. Potato PotAto.

Hasta
Jeff

jtshaw · 01-22-2004, 01:05 PM

Ya, you definitly want to use NULL, there is a big different between something pointing to 0 and something pointing to NULL.

As far as the () ? :, it sucks for readability when statements get more complex then simple if-then-else statements which is why few people use it. In general most new guides to C and C++ tell people to shy away from them in general. I remember a professor I had a in college telling us if he saw those operators in our code we would be repeating his class.

It was his feeling that those, along with goto's, we completely unexceptable in 99.9% of all cases.

I complied and ran this code with a return statement and NULL's and it seams to work fine for me.