ORDER BY in SQL functions

Are ORDER BYs allowed in SQL functions? Or do SQL functions work like
views that are as unordered as their underlting tables?

CREATE FUNCTION foo (INT)
RETURNS SETOF INT AS '
SELECT id
FROM table
WHERE some_colunm > $1
' LANGUAGE 'sql';

works. But if I try

CREATE FUNCTION foo (INT)
RETURNS SETOF INT AS '
SELECT id
FROM table
WHERE some_colunm > $1
ORDER BY some_other_colunm
' LANGUAGE 'sql';

the parser comes back with

ERROR: function declared to return int4 returns multiple values in
final retrieve

The sorting must occur in the function, because once I have a set of
IDs, there is no way to order them by some_other_column.

The function cannot be rewritten in pl/pgsql because it may return more
than one value.

--
K. Ari Krupnikov

DBDOM - bridging XML and relational databases
http://www.iter.co.il