public BinaryExpr(TransitionConditionBinaryExprKind kind, TransitionConditionExpr left, TransitionConditionExpr right)
 {
     this.Left  = left;
     this.Right = right;
     this.Kind  = kind;
 }
 public ExprItem(TransitionConditionBinaryExprKind op)
 {
     this.Op       = op;
     this.Priority = _priorityByOp[op];
     this.Expr     = null;
 }