C++ Gurus

**Iceberg** · 08-25-2007, 12:49 PM

I took a few intensive courses on C++ and Data structures my freshmen year of college. 5 years later I'm a bit rusty, but have a few requests to critique my logic:

Simple function to remove a node in a list of type list, I think I've got the right idea but I'm so damn rusty on pointers it's killing me:

Code:

//This isn't right, but just shows what I'm working with
    struct list() {
        list *next;
        list *prev;
        list *data;
}

//This is the function I wrote
    void remove(list node) {
list *nPrev = node->prev;
list *nNext = node->next;

nPrev->next = nNext;
nNext->prev = nPrev;

delete node;

return 1;
}

=Sarc= · 08-25-2007, 02:39 PM

You probably want to do some kind of comparison with node and the current node you're looking at. If they are the same, delete it.

This part looks funny...

Code:

nPrev->next = nNext;

You probably want that reversed or something...

Code:

nNext = node->next;
nPrev = node->prev;

So you have your references to nodes on either side of the node you want to delete. Make sure they reference each other and deallocate the memory for the node you want to delete.

**Iceberg** · 08-26-2007, 03:04 AM

Hm, I thought that was what I was doing? I thought I was taking the node, selecting its next pointer as a node, and then changing the "next" nodes previous to the original nodes previous. And doing the same with the nodes previous pointer.

Or am I just using them wrong?

=Sarc= · 08-26-2007, 03:26 AM

Ah, I see... I got all mixed up when I first looked at it.

What happens when you run it?

The only other thing that might cause a problem is the function signature. If the function's argument is pass by value, it might not delete when you want it to. You'll have to pass the node argument by reference since the parameter calls for the list struct and not a pointer to a list struct.

Change the function's parameter to

Code:

void remove (list *node)

or call the function with

Code:

remove(&node);

**Iceberg** · 08-26-2007, 03:32 AM

Understood. Right now I haven't been able to run any code, my PC is currently dead.

**Iceberg** · 08-27-2007, 12:16 AM

Ok, what about this:

Code:

void remove() {
	list *nNext = this->next;
	list *nPrev = this->prev;

	nNext ->prev = nPrev ;
	nPrev ->next = nNext ;

	delete this->data;
	delete this;
}

=Sarc= · 08-27-2007, 01:34 AM

It looks ok. It also seems like you changed it so that remove() is an operation on a node object. Everything looks ok logically.

**Iceberg** · 08-27-2007, 01:49 AM

Yeah that's what I did (seems more logical, plus I won't have to check if the node is of type list). Great, thanks for the guidance.

PanzerHans · 08-27-2007, 03:12 AM

Perhaps off topic, but if you are going to do programming these days you might want to look at either Java or .NET. This way you can safely ignore the pesky *'s.

Pointer arithmetics will be a thing of your past.

=Sarc= · 08-27-2007, 11:23 AM

Quote:

Originally Posted by PanzerHans

Perhaps off topic, but if you are going to do programming these days you might want to look at either Java or .NET. This way you can safely ignore the pesky *'s.

Pointer arithmetics will be a thing of your past.

This is a good point. Managed code is much easier to program but... it's managed code. You lose that control you hated so much, which means your program might not run as fast or use the smallest memory footprint.

Managed code would be good for this unless it's a lesson in using pointers. I think it's still good to understand what pointers are and how to use them. Java uses pointers but not in the way you'd think because you never have to think about memory references. This can lead to problems when you accidentally pass a reference to a method instead of a copy of the object or vice versa. You also still need to understand the concept of pointers for linked lists!

**Iceberg** · 08-27-2007, 11:47 AM

This was entirely for a refresher with pointers and linked lists. I've done this all before, but I just needed to wrap my head around it again.

Plus I enjoy the control I get with pointers

Now if I just remembered how to write in C instead of C++ I'd be in line to create some quick peices of code.

Now Assembly language is where the real speed is at

, oh my little microcontrollers how I miss thee.

**WhiskeySix** · 08-27-2007, 11:52 AM

Whenever I'm using linked lists, I use a 'list *pCurrent' pointer and use that as my main reference point. (the notion of a 'current' pointer gets used a lot in real-time code as well)

08-25-2007, 12:49 PM	#1 (permalink)
Iceberg Join Date: Dec 2004 Location: Illinois Age: 25 Posts: 1,929	C++ Gurus I took a few intensive courses on C++ and Data structures my freshmen year of college. 5 years later I'm a bit rusty, but have a few requests to critique my logic: Simple function to remove a node in a list of type list, I think I've got the right idea but I'm so damn rusty on pointers it's killing me: Code: //This isn't right, but just shows what I'm working with struct list() { list next; list prev; list data; } //This is the function I wrote void remove(list node) { list nPrev = node->prev; list nNext = node->next; nPrev->next = nNext; nNext->prev = nPrev; delete node; return 1; } __________________ It only takes 2 bites [insert parasite] to get to the center of a meatpop.* TGNS Admin \| NS Forum Moderator Digz \| NS Play Tester Natural Selection \| TGNS Primer \| Communication Awareness! Army Info: Deployment or Bust - June 2009

08-25-2007, 02:39 PM	#2 (permalink)
=Sarc= Join Date: May 2003 Location: Ottawa, Canada Posts: 4,600	Re: C++ Gurus You probably want to do some kind of comparison with node and the current node you're looking at. If they are the same, delete it. This part looks funny... Code: nPrev->next = nNext; You probably want that reversed or something... Code: nNext = node->next; nPrev = node->prev; So you have your references to nodes on either side of the node you want to delete. Make sure they reference each other and deallocate the memory for the node you want to delete. __________________ JO Guides & Tutorials Team Element - It's who you game with.

08-26-2007, 03:04 AM	#3 (permalink)
Iceberg Join Date: Dec 2004 Location: Illinois Age: 25 Posts: 1,929	Re: C++ Gurus Hm, I thought that was what I was doing? I thought I was taking the node, selecting its next pointer as a node, and then changing the "next" nodes previous to the original nodes previous. And doing the same with the nodes previous pointer. Or am I just using them wrong? __________________ It only takes 2 bites [insert parasite] to get to the center of a meatpop. TGNS Admin \| NS Forum Moderator Digz \| NS Play Tester Natural Selection \| TGNS Primer \| Communication Awareness! Army Info: Deployment or Bust - June 2009

08-26-2007, 03:26 AM	#4 (permalink)
=Sarc= Join Date: May 2003 Location: Ottawa, Canada Posts: 4,600	Re: C++ Gurus Ah, I see... I got all mixed up when I first looked at it. What happens when you run it? The only other thing that might cause a problem is the function signature. If the function's argument is pass by value, it might not delete when you want it to. You'll have to pass the node argument by reference since the parameter calls for the list struct and not a pointer to a list struct. Change the function's parameter to Code: void remove (list *node) or call the function with Code: remove(&node); __________________ JO Guides & Tutorials Team Element - It's who you game with.

08-26-2007, 03:32 AM	#5 (permalink)
Iceberg Join Date: Dec 2004 Location: Illinois Age: 25 Posts: 1,929	Re: C++ Gurus Understood. Right now I haven't been able to run any code, my PC is currently dead. __________________ It only takes 2 bites [insert parasite] to get to the center of a meatpop. TGNS Admin \| NS Forum Moderator Digz \| NS Play Tester Natural Selection \| TGNS Primer \| Communication Awareness! Army Info: Deployment or Bust - June 2009

08-27-2007, 12:16 AM	#6 (permalink)
Iceberg Join Date: Dec 2004 Location: Illinois Age: 25 Posts: 1,929	Re: C++ Gurus Ok, what about this: Code: void remove() { list nNext = this->next; list nPrev = this->prev; nNext ->prev = nPrev ; nPrev ->next = nNext ; delete this->data; delete this; } __________________ It only takes 2 bites [insert parasite] to get to the center of a meatpop. TGNS Admin \| NS Forum Moderator Digz \| NS Play Tester Natural Selection \| TGNS Primer \| Communication Awareness! Army Info: Deployment or Bust - June 2009

08-27-2007, 01:34 AM	#7 (permalink)
=Sarc= Join Date: May 2003 Location: Ottawa, Canada Posts: 4,600	Re: C++ Gurus It looks ok. It also seems like you changed it so that remove() is an operation on a node object. Everything looks ok logically. __________________ JO Guides & Tutorials Team Element - It's who you game with.

08-27-2007, 01:49 AM	#8 (permalink)
Iceberg Join Date: Dec 2004 Location: Illinois Age: 25 Posts: 1,929	Re: C++ Gurus Yeah that's what I did (seems more logical, plus I won't have to check if the node is of type list). Great, thanks for the guidance. __________________ It only takes 2 bites [insert parasite] to get to the center of a meatpop. TGNS Admin \| NS Forum Moderator Digz \| NS Play Tester Natural Selection \| TGNS Primer \| Communication Awareness! Army Info: Deployment or Bust - June 2009

08-27-2007, 03:12 AM	#9 (permalink)
PanzerHans Join Date: Aug 2005 Location: By the PC Age: 35 Posts: 2,259	Re: C++ Gurus Perhaps off topic, but if you are going to do programming these days you might want to look at either Java or .NET. This way you can safely ignore the pesky *'s. Pointer arithmetics will be a thing of your past. __________________ -- VI VI VI - the number of the beast

08-27-2007, 11:47 AM	#11 (permalink)
Iceberg Join Date: Dec 2004 Location: Illinois Age: 25 Posts: 1,929	Re: C++ Gurus This was entirely for a refresher with pointers and linked lists. I've done this all before, but I just needed to wrap my head around it again. Plus I enjoy the control I get with pointers Now if I just remembered how to write in C instead of C++ I'd be in line to create some quick peices of code. Now Assembly language is where the real speed is at , oh my little microcontrollers how I miss thee. __________________ It only takes 2 bites [insert parasite] to get to the center of a meatpop. TGNS Admin \| NS Forum Moderator Digz \| NS Play Tester Natural Selection \| TGNS Primer \| Communication Awareness! Army Info: Deployment or Bust - June 2009

08-27-2007, 11:52 AM	#12 (permalink)
WhiskeySix Join Date: Oct 2005 Location: Gillette Stadium, Section 309, Row 12, Seat 24 Age: 33 Posts: 8,468	Re: C++ Gurus Whenever I'm using linked lists, I use a 'list pCurrent' pointer and use that as my main reference point. (the notion of a 'current' pointer gets used a lot in real-time code as well) __________________ PoE2 Version 2.5 Overview \| Get started with PoE2 (for free!)*

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