Why pointer is not same

Question

Hi

When we have pointer to int, we assing value to pointed variable by using astric like below:

int i ;int* p = &i; *p = 5;

But it is not the case for array as below :

int* p = new int[20];

for(int i=0;i<20;++i)
{
p[i] = i;
}

Why *p[i] is not needed here ?
https://code.sololearn.com/cS86FMTsOyLq/?ref=app

Answer 1

You are creating a pointer for the array not for the array elements. What you're doing inside the loop is accessing the array elements. p holds the address of the array. So u can use the subscript operator.

*p[i] means *(p[i]) --- here p[i] isn't a pointer. The pointer is for the whole array not for a particular element.

I understand this but not sure if I'm explaining this correctly.

Answer 2

1) you don't need asterix when accessing array members because the indexing [] operator is doing that for you.
p[i] is equivalant to *(p+i)

2) as on the surface we only have a pointer to integer ( int *p ), you would need two different delete operator to seperately handle cases where the pointer is pointing to a single integer or an array of integers.

3) regarding that commented area of code : according to standards, if during a brace initialisation the compiler have to perform a narrowing conversion ( type conversion from higher type to a lower type like from double to int in your case ), the code should be considered ill-formatted and it's up to your implementation to throw a warning or error regarding the same.

Answer 3

delete is used to de-allocate memory allocated for single object

delete[] is used to de-allocate memory allocated for array of objects (just like you allocated memory using [])

Answer 4

Yeah i know there are two concepts for pointer and array together

If it's just a pointer for array means only one pointer involved, why delete[] is needed instead of delete

Answer 5

Or my delete[] in code is wrong ?