looping through query to update column

Hello,
I am trying to loop through a table to update one column

create or replace function foo() returns integer as $$
declare
rec RECORD;
row integer := 0;
begin
for rec in select * from table loop
update rec set recordid = row;
row++;
end loop;
return 0;
end;
$$ language plpgsql

In pgadmin, I am getting the following error message, but that does not help me much:
ERROR: syntax error at or near "$1" at character 9
QUERY: update $1 set recordid = $2
CONTEXT: SQL statement in PL/PgSQL function "foo" near line 6

Thanks for any help
JCR