在模板化类中折叠指针？

Question

Here is my code:

template<typename B>
class cvector{

public:

    cvector(){    
    allocatedSize =0;
    actualSize = 0;
    buffer = 0;
    }


    cvector(int k):allocatedSize(k){

    }


    cvector(int k, const B& initial ):allocatedSize(k), actualSize(k){

    buffer = new B[allocatedSize];

        for(int i = 0;i<allocatedSize;i++){
            buffer[i] = initial;
        }   
    }

    ~cvector(){
        delete [] buffer;                   
    }


private:
    int allocatedSize;
    int actualSize;
    B* buffer;

};

int main(int argc, char** argv) {

cvector<int> pee(2,int(5));
cvector<int*> kay(2,new int(10));
return 0;
}

I am trying to emulate std::vector . My code isn't optimized and clean yet as this is just a draft but as of now, i get no problems and here are my test cases when initializing:

cvector<int> p(2,int(5));                   //no error
cvector<int*> k(2,new int(10));             //no error
cvector<int> j(2,new int(5));               // error because it's int
cvector<int*> l(2,int(2));                  //error because it's a pointer

I am curious how are these B expressions evaluated if i will put int or int* ?

B* buffer;                           // (int*)* so int *? (just like reference collapsing?
buffer = new B[allocatedSize];       // new int* if int* ?!

So if i wil use int* then B* buffer; will be int* ? what about buffer = new B[allocatedSize]; and const B& initial from my code?

Answer 1

"Pointer collapsing" doesn´t exist.
No stars will be added or removed or anything else.

B* buffer;
buffer = new B[allocatedSize];  

with B being int results in

int* buffer;
buffer = new int[allocatedSize];  

ie. an array of int , and you can do whatever you want with the int ´s.

With B being int* , it will be

int** buffer;
buffer = new int*[allocatedSize];  

ie. an array of int pointers, all pointers pointing nowhere (initially),
and you can do whatever you want with your pointers.

Answer 2

how are these B expressions evaluated if i will put int or int* ?

For int , the B will be int* and for int* , the B will be int** .

So if i wil use int* then B* buffer; will be int* ? what about buffer = new B[allocatedSize]; and const B& initial from my code?

No. B* will be int** as mentioned above. For int* the expression would look like:

(int**)buffer = new int*[allocatedSize];

The const B& initial would be evaluated as const int*& .

With my advice, for the production code you may think above having std::vector as an object and cvector as a wrapper around it. Or inherit cvector from std::vector in a kind of "has a" relationship.