The following model snippet, I was trying did not work as expected.  The code snippet was based on publication
"Modelling of mixed Continuous/Discrete Systems in Modelica" by Martin et.al.

model tick

  

parameter Real sampleTime = 0.1 ;

Real x(start=0, fixed=true) ;

  

discrete Real nextTime(start=0) ;

  

  equation

  

    when  time  >= pre(nextTime) then    

       nextTime = time + sampleTime ;

    end when;  

   

     x = nextTime ;

end tick;

The above code produces no change in x at all. It remains at zero. But then when I change the when expression to  " time > pre(nextTime)" it works. I get the stair step changes in x.  Is this expected or is it a bug? Some explanation of this behavior would be much appreciated. I am using omc verison v1.9.3-dev.1258+gf9a05a1.