What is the best way to know if an element is " empyt " inside a mapping ?
For example
mapping ( address => uint) balances;
If the user already used the contract there will be an address => "foo" value but if not the mapping still exist it just gives back 0x00000 or something as value.So it's never really empty.
Is there a clean way to check if the value is 0x0000 or something an user inputted for that address?( other than if balances[address] == 0x0000 )
