base class pointer problems

this one has had me stumped for at least the past 2 hours.

i am working on a simple genetic algorithm program with two types of creatures( predator and prey ) both derived from a base class creature.

inside of my world manager class i have 2 pointer arrays, one holding pointers to predators and one holding pointers to prey.

i also have a delete function that accepts a pointer to a creature ( the base class ) and deletes the pointer and sets it to NULL.

whenever a creature dies, however, the pointer isnt completely deleted. i have tried changing the delete function to accept pointers to predators and preys instead of creatures but i get the same problem.

my delete function is merely:

Code:

---

void Delete( Creature * creature )
        {
                delete creature;
                creature = NULL;
        }

---

if you need any more code to solve the problem, let me know...

Sounds more like artificial life than a GA. ;)

It would help to see more code, but I can guess what your problem is. Is your base class destructor virtual? If it isn't, then deleting a pointer to a creature (which is reall say a predator), will slice the class, deleting only the creature portion.

Cheers

Quote:

---

Code:

---

void Delete( Creature * creature )
{
  delete creature;
  creature = NULL;
}

---

---

When you set creature to NULL, it's only setting the local variable creature-- not the variable that you passed in. You can try passing a reference to a pointer:

Code:

---

void Delete(Creature*& creature)
{
  delete creature;
  creature = NULL;
}

---

But that will only change the pointer that you've passed in the function call-- if you have other pointers to that particular creature elsewhere then it won't change them.

-tf

yeah, its an artificial life sim, but i use GA principles to do reproduction, etc...

whether or not the classes get deleted isnt really a concern for me... there is nothing dynamic in them. the important thing was that the pointer get set to NULL.

i just got rid of the function entirely and just replaced every function call with those two lines... :-\

thanks anyway.