contract StandardToken is ERC20 {
  using SafeMath for uint256;

  mapping(address => uint256) balances;
  mapping (address => mapping (address => uint256)) internal allowed;


  uint256 totalSupply_;

  function totalSupply() public view returns (uint256) {
    return totalSupply_;
  }

  function transfer(address _to, uint256 _value) public returns (bool) {
    require(_to != address(0));
    require(_value <= balances[msg.sender]);

    balances[msg.sender] = balances[msg.sender].sub(_value);
    balances[_to] = balances[_to].add(_value);
    emit Transfer(msg.sender, _to, _value);
    return true;
  }

  function balanceOf(address _owner) public view returns (uint256 balance) {
    return balances[_owner];
  }

  function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
    require(_to != address(0));
    require(_value <= balances[_from]);
    require(_value <= allowed[_from][msg.sender]);

    balances[_from] = balances[_from].sub(_value);
    balances[_to] = balances[_to].add(_value);
    allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
    emit Transfer(_from, _to, _value);
    return true;
  }

  function approve(address _spender, uint256 _value) public returns (bool) {
    allowed[msg.sender][_spender] = _value;
    emit Approval(msg.sender, _spender, _value);
    return true;
  }

  function allowance(address _owner, address _spender) public view returns (uint256) {
    return allowed[_owner][_spender];
  }

  /* Approves and then calls the receiving contract */
  function approveAndCall(address _spender, uint256 _value, bytes _extraData) public returns (bool success) {
      allowed[msg.sender][_spender] = _value;
      emit Approval(msg.sender, _spender, _value);

      //call the receiveApproval function on the contract you want to be notified. This crafts the function signature manually so one doesn't have to include a contract in here just for this.
      //receiveApproval(address _from, uint256 _value, address _tokenContract, bytes _extraData)
      //it is assumed that when does this that the call *should* succeed, otherwise one would use vanilla approve instead.
      if(!_spender.call(bytes4(bytes32(keccak256("receiveApproval(address,uint256,address,bytes)"))), msg.sender, _value, this, _extraData)) { revert(); }
      return true;
  }

}
function approveAndCall(address _spender, uint256 _value, bytes _extraData) public returns (bool success) {
    allowed[msg.sender][_spender] = _value;
    emit Approval(msg.sender, _spender, _value);

    //call the receiveApproval function on the contract you want to be notified. This crafts the function signature manually so one doesn't have to include a contract in here just for this.
    //receiveApproval(address _from, uint256 _value, address _tokenContract, bytes _extraData)
    //it is assumed that when does this that the call *should* succeed, otherwise one would use vanilla approve instead.
    if(!_spender.call(bytes4(bytes32(keccak256("receiveApproval(address,uint256,address,bytes)"))), msg.sender, _value, this, _extraData)) { revert(); }
    return true;
}

/* Approves and then calls the receiving contract */