[Ethereum] What does address(0) mean?

addressesmappingsolidity

Referring to this link: https://theethereum.wiki/w/index.php/ERC20_Token_Standard

looking at the last contract. (Line 130)

function totalSupply() public constant returns (uint) {
    return _totalSupply  - balances[address(0)];
}

Why do we use balances[address(0)] here? Is that means we will get the sum of all values in the balances?

Best Answer

balances is a mapping of address to how many tokens that address owns.

balances[address(0)] then means how many tokens the address 0 (0x00000000...00) owns.

Although I don't like the practice, some ERC20 tokens consider tokens that are sent to address 0 to be "burned" and thus don't count them in the total. So _totalSupply - balances[address(0)] gives the total number of tokens minus those that have been "burned" by transferring them to address 0.

Related Solutions

[Ethereum] How to set the initial supply of a token to unlimited in an ethereum contract

The totalSupply will be pretty much limited to the uint256 type: (2^256)-1

What you could do however, is to set the _totalSupply = 0 (or maximum value) and erase all the checks on totalSupply and simply assign balances to the the balances[address] as you wish to.

I'm not aware of any check against totalSupply that's somehow required.

[Ethereum] This contract does not implement all functions and thus cannot be created

The problem is that totalSupply() implementation is missing. Seems like autogenerated getters do not count. So you need to explicitly create the function.

contract StandardToken is Token {
    uint256 _totalSupply;

    function totalSupply() constant returns (uint256 totalSupply) {
        totalSupply = _totalSupply;
    }
}

Best Answer

Related Solutions

[Ethereum] How to set the initial supply of a token to unlimited in an ethereum contract

[Ethereum] This contract does not implement all functions and thus cannot be created

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