Node_M PlusMinus()
        {
            Node_M left = Mult();

            while (true)
            {
                //Identify the operation
                Operation op = Operation.Null;
                if (splitter.current_sign == Sign.Plus)
                {
                    op = Operation.Addition;
                }
                else if (splitter.current_sign == Sign.Minus)
                {
                    op = Operation.Substraction;
                }

                //If no plus or minus sign is found
                if (op == Operation.Null)
                {
                    return(left);
                }

                splitter.Move_sign(); //move to the next sign
                if (splitter.current_sign == Sign.Space)
                {
                    splitter.Move_sign();
                }

                Node_M right = Mult();

                //Create a node with a correspondent binary operation
                left = new NodeMatrBinary(left, right, op);
            }
        }
        Node_M Mult()
        {
            //Check whether the current node is a unary operator
            Node_M left = Unary();

            while (true)
            {
                //Identify the operation
                Operation op = Operation.Null;
                if (splitter.current_sign == Sign.Multiply)
                {
                    op = Operation.Multiplication;
                }

                //If no multiply or divide sign is found
                if (op == Operation.Null)
                {
                    return(left);
                }

                splitter.Move_sign(); //move to the next sign
                if (splitter.current_sign == Sign.Space)
                {
                    splitter.Move_sign();
                }

                //Check whether the current node is a unary operator
                Node_M right = Unary();

                //Create a node with a correspondent binary operation
                left = new NodeMatrBinary(left, right, op);
            }
        }