function [exectime, data] = code(seg, data)switch seg, case 1,  % check what the other nodes are doing  msgin = ttGetMsg;  while ~isempty(msgin)    if ~isempty(msgin.done)      % update the coordinates visited by the group      data.done = union(data.done', msgin.done', 'rows')';      data.visit = setdiff(data.visit', data.done', 'rows')';    end        % Are we heading in the same direction as someone else?    % If so, and if we have lower "priority", then change direction    if ~isempty(data.ref) & ~isempty(data.visit) & ...	  msgin.heading == data.ref & msgin.priority>=data.priority      disp(['node ' num2str(data.nodeID) ...	    ' is heading in the same direction as another node and'])      disp(['  our priority: ' num2str(data.priority) ' other priority: ' ...	    num2str(msgin.priority) '==> we change direction.'])      index = floor((length(data.visit)-1)*rand + 1);      data.ref = data.visit(:,index);    end        msgin = ttGetMsg;  end      % Are we heading to a place that has already been visited?  if ~isempty(data.ref) & ~isempty(data.visit) & ~ ...	isempty(intersect(data.ref', data.done','rows'))    disp(['node ' num2str(data.nodeID) ' is heading to a visited place'])    data.ref = []; %taken care of below  end      % First time or heading to an already visited place  % Choose a random location in the list  if isempty(data.ref)    disp(['node ' num2str(data.nodeID) ' is changing direction'])    index = floor((length(data.visit)-1)*rand + 1);    data.ref = data.visit(:,index);    data.priority = rand;    data.visit = data.visit(:, 1:end~=index);  end    % Have we arrived at out destination?  distance_left = sqrt((data.ref(1)-data.x)^2+(data.ref(2)-data.y)^2);  if ~isempty(data.visit) & distance_left<0.3    disp(['node ' num2str(data.nodeID) ' is visiting ' ...	  'x=' num2str(data.ref(1)') ' y=' num2str(data.ref(2)')])    % Colour it    global vpoint visitPoints;    index = intersect(find(visitPoints(1,:)==data.ref(1)), ...		      find(visitPoints(2,:)==data.ref(2)));    set(vpoint(index),'FaceColor', [0 1 0]);        data.done(:,end+1) = data.ref;    index = floor((length(data.visit)-1)*rand + 1);    data.ref = data.visit(:,index);    data.priority = rand;    data.visit = data.visit(:, 1:end~=index);  end    exectime = 0.002; case 2,  % Read our position  data.x = ttAnalogIn(1);  data.y = ttAnalogIn(2);  % Compute the error and the control signal  e = [data.ref(1)-data.x, data.ref(2)-data.y];  u = 1.*e; %P-controller    % Limit the control signal  umin = -5;  umax = 5;  u = min(umax, u);  u = max(umin, u);      % Output the control signal  ttAnalogOut(1, u(1));  ttAnalogOut(2, u(2));      % Tell the others where we are heading  msgout.sender = data.nodeID;  msgout.heading = [data.ref(1); data.ref(2)];  msgout.priority = data.priority; % How much do we want to visit the point?  msgout.done = data.done;  ttSendMsg(0, msgout, 160);  exectime = 0.002; case 3,  exectime = -1;end