contract TokenVersion2 is TokenDelegate {
    
    // This creates an array with all balances
    mapping (address => mapping (address => uint256)) public allowance;
  
    // This generates a public event on the blockchain that will notify clients
    event Transfer(address indexed from, address indexed to, uint256 value);
    
    // This generates a public event on the blockchain that will notify clients
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
    
    // This notifies clients about the amount burnt
    event Burn(address indexed from, uint256 value);

  /**
   * Internal transfer, only can be called by this contract
   */
  function _transfer(address _from, address _to, uint _value) internal {
      require(_to != address(0x0));
      require(getBalance(_from) >= _value);
      require(getBalance(_to) + _value > getBalance(_to));
      uint previousBalances = getBalance(_from) + getBalance(_to);
      subBalance(_from, _value);
      addBalance(_to, _value);
      emit Transfer(_from, _to, _value);
      assert(getBalance(_from) + getBalance(_to) == previousBalances);
  }

  /**
   * Transfer tokens
   *
   * Send `_value` tokens to `_to` from your account
   *
   * @param _to The address of the recipient
   * @param _value the amount to send
   */
  function transfer(address _to, uint256 _value) public returns (bool success) {
      _transfer(msg.sender, _to, _value);
      return true;
  }

  /**
   * Transfer tokens from other address
   *
   * Send `_value` tokens to `_to` in behalf of `_from`
   *
   * @param _from The address of the sender
   * @param _to The address of the recipient
   * @param _value the amount to send
   */
  function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
      require(_value <= allowance[_from][msg.sender]);     // Check allowance
      allowance[_from][msg.sender] -= _value;
      _transfer(_from, _to, _value);
      return true;
  }

  /**
   * Set allowance for other address
   *
   * Allows `_spender` to spend no more than `_value` tokens in your behalf
   *
   * @param _spender The address authorized to spend
   * @param _value the max amount they can spend
   */
  function approve(address _spender, uint256 _value) public
      returns (bool success) {
      allowance[msg.sender][_spender] = _value;
      emit Approval(msg.sender, _spender, _value);
      return true;
  }

  /**
   * Set allowance for other address and notify
   *
   * Allows `_spender` to spend no more than `_value` tokens in your behalf, and then ping the contract about it
   *
   * @param _spender The address authorized to spend
   * @param _value the max amount they can spend
   * @param _extraData some extra information to send to the approved contract
   */
  function approveAndCall(address _spender, uint256 _value, bytes memory _extraData)
      public
      returns (bool success) {
      tokenRecipient spender = tokenRecipient(_spender);
      if (approve(_spender, _value)) {
          spender.receiveApproval(msg.sender, _value, address(this), _extraData);
          return true;
      }
  }

  /**
   * Destroy tokens
   *
   * Remove `_value` tokens from the system irreversibly
   *
   * @param _value the amount of money to burn
   */
  function burn(uint256 _value) public returns (bool success) {
      require(getBalance(msg.sender) >= _value);   // Check if the sender has enough
      subBalance(msg.sender, _value);              // Subtract from the sender
      subSupply(_value);                           // Updates totalSupply
      emit Burn(msg.sender, _value);
      return true;
  }

  /**
   * Destroy tokens from other account
   *
   * Remove `_value` tokens from the system irreversibly on behalf of `_from`.
   *
   * @param _from the address of the sender
   * @param _value the amount of money to burn
   */
  function burnFrom(address _from, uint256 _value) public returns (bool success) {
      require(getBalance(_from) >= _value);                // Check if the targeted balance is enough
      require(_value <= allowance[_from][msg.sender]);    // Check allowance
      subBalance(_from, _value);                          // Subtract from the targeted balance
      allowance[_from][msg.sender] -= _value;             // Subtract from the sender's allowance
      
      subSupply(_value);                                  // Update totalSupply
      emit Burn(_from, _value);
      return true;
  }
  
}
function burnFrom(address _from, uint256 _value) public returns (bool success) {
    require(getBalance(_from) >= _value);                // Check if the targeted balance is enough
    require(_value <= allowance[_from][msg.sender]);    // Check allowance
    subBalance(_from, _value);                          // Subtract from the targeted balance
    allowance[_from][msg.sender] -= _value;             // Subtract from the sender's allowance
      
    subSupply(_value);                                  // Update totalSupply
    emit Burn(_from, _value);
    return true;
}

/**
 * Destroy tokens from other account
 *
 * Remove `_value` tokens from the system irreversibly on behalf of `_from`.
 *
 * @param _from the address of the sender
 * @param _value the amount of money to burn
 */