convert column of integer type to time type?

Hi,

I want to convert a column of type integer to type 'time without time zone'.

If I have a table with an integer column

some_int
----------
12
345
1622
1

Then, I add a column to the table of type 'time without time zone'
(some_time).
and, I can perform the update:

UPDATE tester SET some_time = CAST (to_char(some_int, 'FM99909:99') AS
time without time zone);

some_int | some_time
----------+-----------
12 | 00:12:00
345 | 03:45:00
1622 | 16:22:00
1 | 00:01:00

My question is: Is it possible to alter the 'some_int' column directly
without having to create a temporary 'some_time' holding column?

Thanks in advance,
C