For now there is no special support for returning values although it may be added at a later version.

To return an int or real result you just use a plain C return statement with the appropriate return value.

To return a NULL value from any function you have to set the variable pointed to by the is_null function parameter to 1.

For strings up to 255 characters long you have to copy the string to the location pointed to by the result paramter and store its length in the varibale pointed to by the length parameter. Returning longer strings requires memory allocation within the UDF and is not yet supported.

datetime values need to be returned as strings for now. 

	// returning an INT
    return 42;

    // returning a REAL
    return 3.14;

    // returning a NULL value for INT or REAL
    *is_null = 1;
    return 0;

    // returing a STRING (up to 255 characters)
    strcpy(result, string);
    *length = strlen(string);
    return;

    // returning a binary safe STRING
    memcpy(result, string, str_len);
    *length = str_len;
    return;

    // returning a NULL STRING
    *is_null = 1;
    return;

    // returing a DATETIME
    strcpy(result, "2000-01-01 00:00:00");
    *length = strlen(result);
    return;