Getting additional memory on the go without pointers

Question

In C++, is it possible to create a new array during program runtime? Specifically, suppose I have a data member in a class and the name of the variable is array, which is an array of size 10. Suppose during runtime I want a bigger array, can I do this without using pointers? Can I have a method as follows?

int[] expandCapacity(int currentCapacity) {
     int [] arr = new int[currentCapacity*2];
     currentCapacity*=2;
     return arr;
}

Why can't I use this method to expand the current array's capacity by saying:

currentCapacity = 10;
array = expandCapacity (currentCapacity);

If this works, there would be no need to use pointers. I feel like I'm missing something crucial here. I'd appreciate if you could point out what I am missing.

Even containers like `std::vector` use pointers internally. There's no getting around them. — chris, Jun 18 '12 at 15:37
Is this just an interlectual exercise or is there a problem you are trying to solve? — Stefan, Jun 18 '12 at 15:38
Besides, pointers are also needed in situation different than "handling chucks of memory of unknown size at compile-time". Take into account, for example, polymorphism by sub-type. A function that returns instances of subclasses of T must be return a T*. — akappa, Jun 18 '12 at 15:40

score 8 · Answer 1 · answered Jun 18 '12 at 15:33

8

No, this is quite impossible.

However, doing it this way yourself is pure insanity. Use std::vector<int> and let your compiler implementer do it all for you.

answered Jun 18 '12 at 15:33

Puppy

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Your wording here is quite odd. The second sentence seems to imply that it _is_ possible. – Mooing Duck Jun 18 '12 at 15:45
I was actually looking into how std::vector is implemented. I wasn't trying to implement a vector class myself. – user1210233 Jun 19 '12 at 08:04

score 3 · Answer 2 · edited May 23 '17 at 12:03

3

You should an STL container like a vector for example.

If this works, there would be no need to use pointers. I feel like I'm missing something crucial here. I'd appreciate if you could point out what I am missing.

pointers are useful for much more than this. I recommend finding a good c++ tutorial(check the c++ FAQ here for more).

edited May 23 '17 at 12:03

Community

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answered Jun 18 '12 at 15:33

WeaselFox

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I meant pointers would not be needed for this particular use, not completely useless. But I understand where I was wrong. I should've specified. Thanks – user1210233 Jun 19 '12 at 08:06

Getting additional memory on the go without pointers

2 Answers2