public override WS1SFormula ToWS1S(CharSetSolver solver)
 {
     if (WS1S == null)
     {
         var l = new MSOIf(left, right).ToWS1S(solver);
         var r = new MSOIf(right, left).ToWS1S(solver);
         WS1S = new WS1SAnd(l, r);
     }
     return(WS1S);
 }
 public override WS1SFormula ToWS1S(CharSetSolver solver)
 {
     if (WS1S == null)
     {
         var l = new MSOIf(left, right).ToWS1S(solver);
         var r = new MSOIf(right, left).ToWS1S(solver);
         WS1S = new WS1SAnd(l,r);
     }
     return WS1S;
 }