Mappings

Check out the following syntax:

mapping (uint => address) public punkIndexToAddress;

This is a special kind of data structure: punkIndexToAddress points to something not unlike an Excel table with two columns. The first column refers to the punk identifier between 0 and 9,999; and the second column contains the address of the owner of the respective punk:

To access the owner value for a punk, we use the following syntax:

address punk0Owner = punkIndexToAddress[0];     // 0xe08c32...44ac0address punk1Owner = punkIndexToAddress[1];     // 0xb88f6...98018// Or if we were to use another variable:uint punk = 2;address punk2Owner = punkIndexToAddress[punk];  // 0x897ae...1dee0

More on statements like that later though...