Doubt about User-defined function.

I have doubt about user-defined function returns value :

* why function returns( accepts ) One attribute in the
arguments of function/table, Otherwise it returns the whole record of the
table. Function accept more than arguments .
* Why it doesn`t return more than one arguments in
the function (or) Attribute of that table.

* Its like same as C-language function, Because in C function
returns one value (or) structure/array of characters.

* My question is, In psql user-defined function doesn`t
returns more than one attribute. Is it possible (or) Not.

Some examples :
i) create function com2(text,integer) returns text as '
select city.city from city,weather
where weather.city=$1 AND city.pop>$2' language sql;

Res : Return type of the function is Text, As well as it
is one of the argument of function.
( At the type of returning, why it doesn`t
also accepts integer ).
ii) create function usrs_tab(text,integer) returns city as
'select city.city,city.pop,city.state from
city,weather where weather.city=$1 AND city.pop>$2' language
sql;

Res : Return one record from City table ( table
contains city, pop, state only ).

Thanking you.

--
sathiyamoorthy