// end existential delay

    private void SetDelay(ISymValue sv, DefAssignLattice.Delay delay) {
      DefAssignLattice.AVal aval = (DefAssignLattice.AVal)this.egraph[sv];
      this.egraph[sv] = aval.SameButWith(delay);
    }
    private void SetAssigned(Variable v, DefAssignLattice.AVal aval) {
      if (v == null) return;

      SetAssignedStatus(v);

      ISymValue sv = this.egraph[v];

      // assignment makes value unknown
      this.egraph.Eliminate(ValueOf, sv);

      this.egraph[sv] = aval;
    }