constant N := 4;
constant M := 5;

variable x[N] < M;

// Want to converge to a state where the array is sorted.
(future & silent)
  (forall i < (N-1) :
   x[i] <= x[i+1]);


process P[i < (N-1)]
{
  write: x[i];
  write: x[i+1];

  // Only permit actions that swap x[i] and x[i+1] values.
  permit:
    ( true --> x[i]:=x[i+1]; x[i+1]:=x[i]; )
    ;

  puppet action:
    ( x[i] > x[i+1] --> x[i]:=x[i+1]; x[i+1]:=x[i]; )
    ;
}