SELECT in a function != SELECT ?

While trying to formulate an answer to another user's query on this list, I
came a across what I think is strange behaviour in an SQL funsction:

The 3rd column of my 'contacts' table is 'first_name'.

A regular select will allow me to find this:

SELECT a.attname FROM pg_class c, pg_attribute a       WHERE c.relname = 'contacts'       and a.attnum = 3 and
a.attrelid=c.oid;
 attname
------------first_name
(1 row)


But when turned into a function:

CREATE FUNCTION get_colname (name,smallint)
RETURNS name AS '       SELECT a.attname FROM pg_class c, pg_attribute a       WHERE c.relname = ''$1''       and
a.attnum= $2 and a.attrelid=c.oid
 
'
LANGUAGE SQL;

SELECT get_colname('contacts',3);
get_colname
-------------

(1 row)


The result is empty!?

Even more strange:

SELECT 'x'||get_colname('contacts',3)||'x' as foo;
foo
-----

(1 row)

Should I not be seeing "xx" as the result here!? What's going on? Anyone
wknow why the above function get_colname isn't doing what I expect?

Regards,
Ian Morgan
-- 
-------------------------------------------------------------------Ian E. Morgan        Vice President & C.O.O.
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