contract LibRelayer {

    /**
     * Mapping of relayerAddress => delegateAddress
     */
    mapping (address => mapping (address => bool)) public relayerDelegates;

    /**
     * Mapping of relayerAddress => whether relayer is opted out of the liquidity incentive system
     */
    mapping (address => bool) hasExited;

    event RelayerApproveDelegate(address indexed relayer, address indexed delegate);
    event RelayerRevokeDelegate(address indexed relayer, address indexed delegate);

    event RelayerExit(address indexed relayer);
    event RelayerJoin(address indexed relayer);

    /**
     * Approve an address to match orders on behalf of msg.sender
     */
    function approveDelegate(address delegate) external {
        relayerDelegates[msg.sender][delegate] = true;
        emit RelayerApproveDelegate(msg.sender, delegate);
    }

    /**
     * Revoke an existing delegate
     */
    function revokeDelegate(address delegate) external {
        relayerDelegates[msg.sender][delegate] = false;
        emit RelayerRevokeDelegate(msg.sender, delegate);
    }

    /**
     * @return true if msg.sender is allowed to match orders which belong to relayer
     */
    function canMatchOrdersFrom(address relayer) public view returns(bool) {
        return msg.sender == relayer || relayerDelegates[relayer][msg.sender] == true;
    }

    /**
     * Join the Zeedex incentive system.
     */
    function joinIncentiveSystem() external {
        delete hasExited[msg.sender];
        emit RelayerJoin(msg.sender);
    }

    /**
     * Exit the Zeedex incentive system.
     * For relayers that choose to opt-out, the Zeedex Protocol
     * effective becomes a tokenless protocol.
     */
    function exitIncentiveSystem() external {
        hasExited[msg.sender] = true;
        emit RelayerExit(msg.sender);
    }

    /**
     * @return true if relayer is participating in the Zeedex incentive system.
     */
    function isParticipant(address relayer) public view returns(bool) {
        return !hasExited[relayer];
    }
}
/**
 * @title LibRelayer provides two distinct features for relayers.
 *
 * First, Relayers can opt into or out of the Zeedex liquidity incentive system.
 *
 * Second, a relayer can register a delegate address.
 * Delegates can send matching requests on behalf of relayers.
 * The delegate scheme allows additional possibilities for smart contract interaction.
 * on behalf of the relayer.
 */
function isParticipant(address relayer) public view returns(bool) {
        return !hasExited[relayer];
    }
/**
 * @return true if relayer is participating in the Zeedex incentive system.
 */