contract ERC20 is ERC223Basic {
  // active supply of tokens
  function activeSupply() constant returns (uint256);
  function allowance(address _owner, address _spender) constant returns (uint256);
  function transferFrom(address _from, address _to, uint _value) returns (bool);
  function approve(address _spender, uint256 _value);
  event Approval(address indexed owner, address indexed spender, uint256 value);
}
/*
 * ERC20 interface
 * see https://github.com/ethereum/EIPs/issues/20
 */
function activeSupply() constant returns (uint256);

// active supply of tokens