contract StandardToken is BasicToken, ERC20 {

  /* Token supply got increased and a new owner received these tokens */
  event Minted(address receiver, uint amount);

  mapping (address => mapping (address => uint)) allowed;

  /* Interface declaration */
  function isToken() public constant returns (bool weAre) {
    return true;
  }

  /**
   * @dev Transfer tokens from one address to another
   * @param _from address The address which you want to send tokens from
   * @param _to address The address which you want to transfer to
   * @param _value uint the amout of tokens to be transfered
   */
  function transferFrom(address _from, address _to, uint _value) public returns (bool success) {
    uint _allowance = allowed[_from][msg.sender];

    // Check is not needed because sub(_allowance, _value) will already throw if this condition is not met
    // require(_value <= _allowance);
    // SafeMath uses assert instead of require though, beware when using an analysis tool

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

  /**
   * @dev Aprove the passed address to spend the specified amount of tokens on behalf of msg.sender.
   * @param _spender The address which will spend the funds.
   * @param _value The amount of tokens to be spent.
   */
  function approve(address _spender, uint _value) public returns (bool success) {

    // To change the approve amount you first have to reduce the addresses'
    //  allowance to zero by calling `approve(_spender, 0)` if it is not
    //  already 0 to mitigate the race condition described here:
    //  https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
    require (_value == 0 || allowed[msg.sender][_spender] == 0);

    allowed[msg.sender][_spender] = _value;
    Approval(msg.sender, _spender, _value);
    return true;
  }

  /**
   * @dev Function to check the amount of tokens than an owner allowed to a spender.
   * @param _owner address The address which owns the funds.
   * @param _spender address The address which will spend the funds.
   * @return A uint specifing the amount of tokens still avaible for the spender.
   */
  function allowance(address _owner, address _spender) public constant returns (uint remaining) {
    return allowed[_owner][_spender];
  }

  /**
   * Atomic increment of approved spending
   *
   * Works around https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
   *
   */
  function addApproval(address _spender, uint _addedValue) public
  returns (bool success) {
      uint oldValue = allowed[msg.sender][_spender];
      allowed[msg.sender][_spender] = oldValue.add(_addedValue);
      Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
      return true;
  }

  /**
   * Atomic decrement of approved spending.
   *
   * Works around https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
   */
  function subApproval(address _spender, uint _subtractedValue) public
  returns (bool success) {

      uint oldVal = allowed[msg.sender][_spender];

      if (_subtractedValue > oldVal) {
          allowed[msg.sender][_spender] = 0;
      } else {
          allowed[msg.sender][_spender] = oldVal.sub(_subtractedValue);
      }
      Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
      return true;
  }
  
}
/**
 * @title Standard ERC20 token
 *
 * @dev Implementation of the basic standard token.
 * @dev https://github.com/ethereum/EIPs/issues/20
 */
function subApproval(address _spender, uint _subtractedValue) public
returns (bool success) {

    uint oldVal = allowed[msg.sender][_spender];

    if (_subtractedValue > oldVal) {
        allowed[msg.sender][_spender] = 0;
    } else {
        allowed[msg.sender][_spender] = oldVal.sub(_subtractedValue);
    }
    Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
    return true;
}

/**
 * Atomic decrement of approved spending.
 *
 * Works around https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
 */