MySQL stored function to convert formula to list of numbers

Execution example.sql

# Given alphanumeric string that includes two special characters + and -. 
# Dash "-" means range, "+" (plus) means inclusion of number to list.
# Please execute RangeFormulaToList.sql to create function before running test below.
# Examples:

DROP TABLE IF EXISTS `tests_formulas`;
CREATE TABLE `tests_formulas` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `formula` text DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB;

INSERT INTO `tests_formulas` (`id`, `formula`)
VALUES
	(1, '1-3+5'),
	(2, '10-20+30'),
	(3, '1-9+10+11-19');

SELECT 
  formula,
  RangeFormulaToList(formula) as list
FROM tests_formulas;

RangeFormulaToList.sql

DELIMITER //

CREATE FUNCTION RangeFormulaToList(input_string VARCHAR(255))
RETURNS TEXT
DETERMINISTIC
BEGIN
    DECLARE output_list TEXT DEFAULT '';
    DECLARE current_part VARCHAR(255);
    DECLARE range_start INT;
    DECLARE range_end INT;
    DECLARE range_separator_pos INT;
    DECLARE plus_separator_pos INT;
    DECLARE current_number INT;
    DECLARE delimiter_pos INT;

    -- Replace '+' with ','
    SET input_string = REPLACE(input_string, '+', ',');

    -- Add a comma at the end to ensure the last number is processed
    SET input_string = CONCAT(input_string, ',');

    -- Process each part of the input string
    WHILE LENGTH(input_string) > 0 DO
        -- Find the position of the next comma delimiter
        SET delimiter_pos = INSTR(input_string, ',');
        -- Extract the current part
        SET current_part = TRIM(SUBSTRING(input_string, 1, delimiter_pos - 1));
        -- Remove the processed part from the input string
        SET input_string = SUBSTRING(input_string, delimiter_pos + 1);

        -- Find the position of the range separator '-'
        SET range_separator_pos = INSTR(current_part, '-');
        IF range_separator_pos > 0 THEN
            -- If a range separator is found
            SET range_start = CAST(SUBSTRING_INDEX(current_part, '-', 1) AS UNSIGNED);
            SET range_end = CAST(SUBSTRING_INDEX(current_part, '-', -1) AS UNSIGNED);

            -- Append the range to the output list
            WHILE range_start <= range_end DO
                SET output_list = CONCAT(output_list, IF(output_list = '', '', ','), range_start);
                SET range_start = range_start + 1;
            END WHILE;
        ELSE
            -- If no range separator is found, it's a single number
            SET current_number = CAST(current_part AS UNSIGNED);
            SET output_list = CONCAT(output_list, IF(output_list = '', '', ','), current_number);
        END IF;
    END WHILE;

    RETURN (output_list);
END//
DELIMITER ;