C++ operator[] magic [duplicate]

Question

I met a strange way of the appeal to an element of the array and thought it`s a mistake but it works. Can you explain how it works?

#include <iostream>
int main()
{
  int a[] = {1,2,3,4};
  std::cout << 1[a];
}

Answer 1

Expression a[b] is equivalent to *(a + b) so in your example we have:

1[a] which can be written as *(1 + a) which is the same as *(a + 1) which is finally the same as a[1]

Answer 2

BaseAddr[ Offset ] = *( BaseAddr + Offset )
Offset[ BaseAddr ] = *( Offset + BaseAddr ) = *( BaseAddr + Offset )