Concatenating ints and converting to time format

I'm working with SQL Anywhere and I'm writting a function and have a little problem with converting ints (Hour and Minute) to time. Can you help me?

ALTER FUNCTION "DBA"."VisitTime"
RETURNS TIME
DETERMINISTIC
BEGIN
     DECLARE "timeV" time
     DECLARE hourV integer;
     DECLARE minuteV integer;
     DECLARE minutesV integer;
     SELECT HOUR(CURRENT TIME) as hourV;
     SELECT MINUTE(CURRENT TIME) as minuteV;
     IF minuteV BETWEEN 0 and 29
     THEN SET minutesV = 30;
     END开发者_JAVA百科 IF;
     IF minuteV between 30 and 59
     THEN SET minutesV = 00;
          SET hourV = hourV + 1;
          IF hourV >= 24 THEN SET hourV = 0;
          END IF;
     END IF;

     SET timeV = CAST(hourV || ':' || minutesV as time);
RETURN "timeV";
END;

What I do wrong? When I try to execute this I've got ERROR ("Result set not permitted in VisitTime")

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I'm not a sqlanywhere guy, but deterministic means that given the same data and the same input/query you will get the same output. Said another way (SQL Server documentation)

Deterministic functions always return the same result any time they are called with a specific set of input values and given the same state of the database. Nondeterministic functions may return different results each time they are called with a specific set of input values even if the database state that they access remains the same.

In your case your function, you reference CURRENT TIME, making the function NON-deterministic because the mere passing of time makes results differ.