operator[] on basic types with pointer argument

Question

What happening in following code?

int main()
{
    int i = 37;
    int* pi = &i;
    i[pi];  //works
    i[0];   //error C2109: subscript requires array or pointer type
}

Why is allowed to indexing int with pointer argument and what does it do?

in C++, array indexing is explicitly implemented using (commutative) pointer arithmetic (along the lines of `*(pi + i)`) and it was left so that `pi[i]` and `i[pi]` behaved the same. in the second case, writing `i[reinterpret_cast(0)]` would do as you expected, i.e. undefined behavior as it dereferences a null pointer — obataku, Jul 01 '16 at 13:53

score 0 · Answer 1 · answered Jul 01 '16 at 13:51

0

i[pi] is the same as *(i + pi).

answered Jul 01 '16 at 13:51

Jarod42

1 Answers1