Protect PL/PGSQL source

Hello,

Does anyone knows if it´s possible to protect from users see a PL/PGSQL
source ?

I have a PL/PGSQL function and I want to make it invisible to users.

Just a example, in Oracle there is a option like this:
http://www.dbasupport.com/oracle/ora9i/wrap_utility.shtml

Regards,

Wilton Ruffato Wonrath
wrwonrath@yahoo.com.br
São Paulo - Brazil
PostgreSQL 8.2