to_char/to_number loses sign

This is from one of the examples in the documentation:

SELECT to_char(-485, '999S');to_char
---------485-

The reverse doesn't work as well:

SEKLECT to_number('485-', '999S');to_number
-----------      485

Is this a bug or intentional?

-- 
Peter Eisentraut
http://developer.postgresql.org/~petere/