ROWTYPE initialization question

'lo list,

I have a plpgsql SP where I loop through a cursor. I have an internal
variable that keeps the previous row, so that I can compare it with the
current row in the cursor.
Like so;

DECLARE
     current table%ROWTYPE;
     previous table%ROWTYPE;
BEGIN
     LOOP
    FETCH tableCur INTO current;

    -- Do stuff

But, in this loop I need to compare the previous row to the current one.
To do that I need to know whether a row was assigned to 'previous', or
there'll be very little to compare (if it doesn't throw an error).
How do I check for that?

I guess it would be like this, but I'd like to be sure.

    IF previous IS NOT NULL
    THEN
        -- Compare previous and current column values
    END IF

    previous := current;
     END LOOP;
END;

Thanks in advance,
--
Alban Hertroys
alban@magproductions.nl

magproductions b.v.

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