C++ operator[] magic

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]

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