Question

I am learning C++ and was reading a book on it where I came across this:

struct Vector{
   int size;
   double* elem;
}

void vector_init(Vector& v, int s){
   v.size = s;
   v.elem = new double[s];
}

So here, would void vector_init(Vector v, int s), without the reference operator, be wrong? Do I have to manually pass by reference using & while passing objects, structs, arrays or anything else as parameters? Also are there any alternate ways to do this? like say void vector_init(Vector *v, int s)?

Any help is appreciated.

Answer 1

would void vector_init(Vector v, int s), without the reference operator, be wrong?

If you don’t pass v by reference, a copy of v will be made when enters function vector_init and you operate on that copy. After vector_init returns that temporary copy will be destroyed, so vector_init has no effect to your original v. To manipulate on original v, you need to pass v by reference(same to other type).

Also are there any alternate ways to do this? like say void vector_init(Vector *v, int s)?

Pass by reference is better choice compare to pass by pointer.