how to call a function from stored proc in mysql code example

Example: mysql create function

-- MySQL

-- example
DELIMITER $$
CREATE FUNCTION f_employee_count(p_dept_no INTEGER) RETURNS INTEGER
  DETERMINISTIC NO SQL READS SQL DATA
  BEGIN
    DECLARE v_emp_count INTEGER;

    SELECT COUNT(*)
    INTO v_emp_count
    FROM EMPLOYEES E
    WHERE E.DEPT_NO = p_dept_no
    GROUP BY DEPARTMENT_NO;

    RETURN v_emp_count;
END$$
DELIMITER ;

/* syntax:
DELIMITER $$
CREATE FUNCTION <Your-procedure-name>(<arguments>) RETURNS <date-type>
  DETERMINISTIC NO SQL READS SQL DATA
  BEGIN
      DECLARE <variable-name> <data-type>

      <Code-that-sets-the-output-variable>; 

      RETURN <variable-name>;
END$$
DELIMITER ;
*/