% TODO: We probably need to unify these (at least for the thesis)
predicate random_allocation(array[int] of int: sol) =
    forall(i in courses) (
        (uniform(0,99) < 80) -> (period_of[i] == sol[i])
    );

predicate free_period() =
let { int: period = uniform(periods) } in
    forall(i in courses where sol(period_of[i]) != period)
          (period_of[i] = sol(period_of[i]));