contract BurnableToken is BasicToken {

event Burn(address indexed burner, uint256 value);

/**
* @dev Burns a specific amount of tokens.
* @param _value The amount of token to be burned.
*/
function burn(uint256 _value) public {
_burn(msg.sender, _value);
}

function _burn(address _who, uint256 _value) internal {
require(_value <= balances[_who]);
// no need to require value <= totalSupply, since that would imply the
// sender's balance is greater than the totalSupply, which *should* be an assertion failure

balances[_who] = balances[_who].sub(_value);
totalSupply_ = totalSupply_.sub(_value);
emit Burn(_who, _value);
emit Transfer(_who, address(0), _value);
}
}
/**
 * @title Burnable Token
 * @dev Token that can be irreversibly burned (destroyed).
 */
function burn(uint256 _value) public {
_burn(msg.sender, _value);
}

/**
 * @dev Burns a specific amount of tokens.
 * @param _value The amount of token to be burned.
 */