public void Visit(SubtractionExpression expression)
        {
            // Handle left:
            expression.LeftArithmeticExpression.Accept(this);

            Console.Write(" - ");

            // Handle right:
            expression.RightArithmeticExpression.Accept(this);
        }
        public void Visit(SubtractionExpression expression)
        {
            // Handle left:
            expression.LeftArithmeticExpression.Accept(this);

            Console.Write(" - ");

            // Handle right:
            expression.RightArithmeticExpression.Accept(this);
        }