Pointers to classes

[kishor8dm]

I have an array of classes. The size of the array is unknown. For this, I used a pointer as follows.

myclass *ptr;
myclass var1, var2, var3; // test variables
ptr = new myclass;
*ptr = var1;
*(ptr+1)=var2;
*(ptr+2)=var3;

Is this legal ? or do i need to include another line ptr+1=new myclass;

[Disch]

This is legal syntax, but it is illegal in that it will cause memory corruption (arguably the worst thing you can do).

*(ptr+1) = var2; is the same thing as ptr[1] = var2. What you're doing is you're trying to set the 2nd object in the array. The problem is, there ISN'T a second object in the array -- you only created one object.

If you want 3 objects, then allocate 3 of them:

ptr = new myclass[3];  // make 3

*ptr = var1;   // now this will all work
*(ptr+1)=var2;
*(ptr+2)=var3;

*(ptr+3)=var4;  // but this is bad!  There isn't a 4th!

// also, don't forget to delete[] what you made with new[]
delete[] ptr;

[chrisname]

The size of the array is unknown

Use a vector; they're dynamic, so you can append and... de-append (?) (or std::vector::push_back() and std::vector::pop_back()) as much as you want as long as you don't try to pop_back() a 0-size vector or something.

As for whether or not you can actually do what you're trying to do above, I'm not sure what exactly you're trying to do.

FUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU

[Disch]

Woah, I missed the whole "size of the array is unknown" bit.

You're better off with vector or list or something in that case. Just add new items as needed.

[helios]

What does OP mean by "the size of the array is unknown"? That the final size is unknown, or that he receives an array of unknown size?

[kishor8dm]

I am attempting a branched linked list. Each node can have arbitrary number of branches (Not a binary tree). The actual structure would be defined in main(). Disch: I think you are right, in my current implementation, i think there are some problems which i suspect are due to the memory corruption. If i define a tree in a particular order, things work out fine. But if the same topology is defined in a different order, the stored data gets corrupted.

Perhaps i should use try vectors. That should work.

[helios]

That's called an n-ary tree. Lists have no branches.

[kishor8dm]

Alright. Now i know what it is called. thanks.