library Roles {
	struct Role {
		mapping (address => bool) bearer;
	}

	/**
	 * @dev give an account access to this role
	 */
	function add(Role storage role, address account) internal {
		require(account != address(0));
		require(!has(role, account));

		role.bearer[account] = true;
	}

	/**
	 * @dev remove an account's access to this role
	 */
	function remove(Role storage role, address account) internal {
		require(account != address(0));
		require(has(role, account));

		role.bearer[account] = false;
	}

	/**
	 * @dev check if an account has this role
	 * @return bool
	 */
	function has(Role storage role, address account) internal view returns (bool) {
		require(account != address(0));
		return role.bearer[account];
	}
}
/**
 * @title Roles
 * @dev Library for managing addresses assigned to a Role.
 */
function add(Role storage role, address account) internal {
	require(account != address(0));
	require(!has(role, account));

	role.bearer[account] = true;
}

/**
 	 * @dev give an account access to this role
 	 */