% An example from C. Marriott and C. DeLisle, Effects of 
% discontinuities in the behavior of a delay differential 
% equation, Physica D, 36 (1989), pp. 198-206.

% The parameter state = +1 if ylag >= -0.427, -1 otherwise.  
% With this definition of history, state is initially +1.

state = +1;
opts = ddeset('Events','exam7e');
sol = dde23('exam7f',12,0.6,[0, 120],opts,state);
while sol.x(end) < 120
   fprintf('Restart at %5.1f.\n',sol.x(end));
   state = - state;
   sol = dde23('exam7f',12,sol,[sol.x(end), 120],opts,state);
end

plot(sol.x,sol.y);
title('Figure 7. Marriott-DeLisle Controller Problem')
xlabel('Restart each time y(t - 12) = -0.427.');