pg_user, pg_group and arrays

Hi!

I would like if there is any way to retrieve all users in a group in an
"elegant way":

Something like the following but without errors:

select usename from pg_user where usesysid in ( select grolist from
pg_group);
ERROR: Unable to identify an operator '=' for types 'int4' and '_int4'
You will have to retype this query using an explicit cast

Another way :
select usename from pg_user where usesysid in ( select grolist[1] from
pg_group where groname='tecnico')
union
select usename from pg_user where usesysid in ( select grolist[2] from
pg_group where groname='tecnico')
union
select usename from pg_user where usesysid in ( select grolist[3] from
pg_group where groname='tecnico')
union
select usename from pg_user where usesysid in ( select grolist[4] from
pg_group where groname='tecnico');

Perhaps a function in SPL ?

TIA

--
Evelio Martínez